The immune system Immune system The body's defense mechanism against foreign organisms or substances and deviant native cells. It includes the humoral immune response and the cell-mediated response and consists of a complex of interrelated cellular, molecular, and genetic components. Primary Lymphatic Organs is equipped with a varied repertoire of defense mechanisms Defense mechanisms Defense mechanisms are normal subconscious means of resolving inner conflicts between an individual's subjective moral sense and their thoughts, feelings, or actions. Defense mechanisms serve to protect the self from unpleasant feelings (anxiety, shame, and/or guilt) and are divided into pathologic, immature, mature, neurotic, and other types. Defense Mechanisms against pathogens. Functionally, the immune system Immune system The body's defense mechanism against foreign organisms or substances and deviant native cells. It includes the humoral immune response and the cell-mediated response and consists of a complex of interrelated cellular, molecular, and genetic components. Primary Lymphatic Organs is differentiated into the innate and adaptive components. Innate immunity, the 1st protective layer of defense, is a system that recognizes threatening microbes, distinguishes self-tissues from pathogens, and subsequently eliminates the foreign invaders. The response is nonspecific and uses different layers of protection: barriers such as the skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions, pattern recognition receptors Receptors Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell. Receptors (PRRs) as well as circulating proteins Proteins Linear polypeptides that are synthesized on ribosomes and may be further modified, crosslinked, cleaved, or assembled into complex proteins with several subunits. The specific sequence of amino acids determines the shape the polypeptide will take, during protein folding, and the function of the protein. Energy Homeostasis (e.g., complement) that relay signals of a threat, and immune cells that help eliminate the microbe. Pathogen-associated molecular patterns Pathogen-Associated Molecular Patterns Sepsis and Septic Shock ( PAMPs PAMPs Sepsis and Septic Shock) in microorganisms and damage-associated molecular patterns Damage-Associated Molecular Patterns Sepsis and Septic Shock (DAMPs) from injured tissues are identified, and the appropriate cells are recruited. Involved cells include phagocytes and accessory cells. The offending pathogens are engulfed by phagocytes for destruction. In antigen Antigen Substances that are recognized by the immune system and induce an immune reaction. Vaccination-presenting cells (the most potent of which is the dendritic cell), parts of the pathogen material or peptides are transported to the cell surface. Through a unique antigen Antigen Substances that are recognized by the immune system and induce an immune reaction. Vaccination-loading mechanism specific to MHC I or II, the processed antigen Antigen Substances that are recognized by the immune system and induce an immune reaction. Vaccination peptides are then presented to the appropriate T cells T cells Lymphocytes responsible for cell-mediated immunity. Two types have been identified - cytotoxic (t-lymphocytes, cytotoxic) and helper T-lymphocytes (t-lymphocytes, helper-inducer). They are formed when lymphocytes circulate through the thymus gland and differentiate to thymocytes. When exposed to an antigen, they divide rapidly and produce large numbers of new T cells sensitized to that antigen. T cells: Types and Functions, leading to T-cell activation. This interaction links innate immunity with adaptive immunity.
Last updated: 25 Mar, 2022
The immune system Immune system The body’s defense mechanism against foreign organisms or substances and deviant native cells. It includes the humoral immune response and the cell-mediated response and consists of a complex of interrelated cellular, molecular, and genetic components. Primary Lymphatic Organs provides defense (immunity) against invading pathogens ranging from viruses Viruses Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells. Virology to parasites, and components are interconnected by blood and the lymphatic circulation Circulation The movement of the blood as it is pumped through the cardiovascular system. ABCDE Assessment.
There are 2 lines of defense Lines of Defense Inflammation (that overlap):
Innate immunity | Adaptive immunity | |
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Genetics Genetics Genetics is the study of genes and their functions and behaviors. Basic Terms of Genetics | Germline encoded | Gene Gene A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms. Basic Terms of Genetics rearrangements involved in lymphocyte development |
Immune response | Nonspecific | Highly specific |
Timing of response | Immediate (minutes to hours) | Develops over a longer period of time |
Memory Memory Complex mental function having four distinct phases: (1) memorizing or learning, (2) retention, (3) recall, and (4) recognition. Clinically, it is usually subdivided into immediate, recent, and remote memory. Psychiatric Assessment response | None | Responds quickly upon recognition of antigen Antigen Substances that are recognized by the immune system and induce an immune reaction. Vaccination with memory Memory Complex mental function having four distinct phases: (1) memorizing or learning, (2) retention, (3) recall, and (4) recognition. Clinically, it is usually subdivided into immediate, recent, and remote memory. Psychiatric Assessment response |
Recognition of pathogen | Pattern recognition receptors Receptors Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell. Receptors (PRRs) such as TLRs recognize pathogen-associated molecular patterns Pathogen-Associated Molecular Patterns Sepsis and Septic Shock ( PAMPs PAMPs Sepsis and Septic Shock) |
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Components |
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Stem cells differentiate into 2 pathways:
Myeloid pathways produce
erythrocytes
Erythrocytes
Erythrocytes, or red blood cells (RBCs), are the most abundant cells in the blood. While erythrocytes in the fetus are initially produced in the yolk sac then the liver, the bone marrow eventually becomes the main site of production.
Erythrocytes: Histology,
platelets
Platelets
Platelets are small cell fragments involved in hemostasis. Thrombopoiesis takes place primarily in the bone marrow through a series of cell differentiation and is influenced by several cytokines. Platelets are formed after fragmentation of the megakaryocyte cytoplasm.
Platelets: Histology, and cells of the
innate immune response
Innate Immune Response
Immunity to pathogens is divided into innate and adaptive immune responses. The innate immune response is the 1st line of defense against a variety of pathogens, including bacteria, fungi, viruses, and parasites. In essentially the same form, the innate type of immunity is present in all multicellular organisms.
Innate Immunity: Barriers, Complement, and Cytokines. Lymphoid pathways produce the cells of adaptive response and
natural killer cells
Natural killer cells
A specialized subset of T-lymphocytes that exhibit features of innate immunity similar to that of natural killer cells. They are reactive to glycolipids presented in the context of the major histocompatibility complex (MHC) class I-like molecule, CD1D antigen.
Lymphocytes: Histology.
Phagocytes “eat” the foreign material, and help detect, clear, and repair damaged tissue, recognizing pathogens via PRRs or opsonization (by complement or immunoglobulins Immunoglobulins Immunoglobulins (Igs), also known as antibodies, are glycoprotein molecules produced by plasma cells that act in immune responses by recognizing and binding particular antigens. The various Ig classes are IgG (the most abundant), IgM, IgE, IgD, and IgA, which differ in their biologic features, structure, target specificity, and distribution. Immunoglobulins: Types and Functions).
Neutrophil:
Granulocyte with multilobed
nucleus
Nucleus
Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus.
The Cell: Organelles and fine faintly pink granules
Mechanism of neutrophil extracellular trap (NET)
release
Release
Release of a virus from the host cell following virus assembly and maturation. Egress can occur by host cell lysis, exocytosis, or budding through the plasma membrane.
Virology:
Neutrophils are stimulated by contact with
bacteria
Bacteria
Bacteria are prokaryotic single-celled microorganisms that are metabolically active and divide by binary fission. Some of these organisms play a significant role in the pathogenesis of diseases.
Bacteriology,
protozoa
Protozoa
Nitroimidazoles,
fungi
Fungi
A kingdom of eukaryotic, heterotrophic organisms that live parasitically as saprobes, including mushrooms; yeasts; smuts, molds, etc. They reproduce either sexually or asexually, and have life cycles that range from simple to complex. Filamentous fungi, commonly known as molds, refer to those that grow as multicellular colonies.
Mycology (
yeast
Yeast
A general term for single-celled rounded fungi that reproduce by budding. Brewers’ and bakers’ yeasts are saccharomyces cerevisiae; therapeutic dried yeast is yeast, dried.
Mycology and
hyphae
Hyphae
Microscopic threadlike filaments in fungi that are filled with a layer of protoplasm. Collectively, the hyphae make up the mycelium.
Mycology forms), which leads to: (a) Ultrastructural alterations of nuclear shape with
chromatin
Chromatin
The material of chromosomes. It is a complex of dna; histones; and nonhistone proteins found within the nucleus of a cell.
DNA Types and Structure decondensation and a swollen and fragmented nuclear membrane, which allows the association of granules and cytoplasmic
proteins
Proteins
Linear polypeptides that are synthesized on ribosomes and may be further modified, crosslinked, cleaved, or assembled into complex proteins with several subunits. The specific sequence of amino acids determines the shape the polypeptide will take, during protein folding, and the function of the protein.
Energy Homeostasis with the
chromatin
Chromatin
The material of chromosomes. It is a complex of dna; histones; and nonhistone proteins found within the nucleus of a cell.
DNA Types and Structure, and (b)
release
Release
Release of a virus from the host cell following virus assembly and maturation. Egress can occur by host cell lysis, exocytosis, or budding through the plasma membrane.
Virology of extracellular structures consisting of a
DNA
DNA
A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine).
DNA Types and Structure backbone, decorated with
histones
Histones
Small chromosomal proteins (approx 12-20 kd) possessing an open, unfolded structure and attached to the DNA in cell nuclei by ionic linkages. Classification into the various types (designated histone I, histone II, etc.) is based on the relative amounts of arginine and lysine in each.
DNA Types and Structure, neutrophil, granular, and cytoplasmic
proteins
Proteins
Linear polypeptides that are synthesized on ribosomes and may be further modified, crosslinked, cleaved, or assembled into complex proteins with several subunits. The specific sequence of amino acids determines the shape the polypeptide will take, during protein folding, and the function of the protein.
Energy Homeostasis (NETs), which ensnare and kill microorganisms.
Monocyte development starts from
hematopoietic stem cells
Hematopoietic stem cells
Progenitor cells from which all blood cells derived. They are found primarily in the bone marrow and also in small numbers in the peripheral blood.
Bone Marrow: Composition and Hematopoiesis (HSCs) and progresses through stages to the colony-forming unit granulocyte-macrophage (CFU-GM):
The 1st monocyte precursor is the
monoblast
Monoblast
White Myeloid Cells: Histology, which has a round or oval
nucleus
Nucleus
Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus.
The Cell: Organelles.
The
promonocyte
Promonocyte
White Myeloid Cells: Histology follows and has a convoluted
nucleus
Nucleus
Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus.
The Cell: Organelles.
The monocyte arises with an indented
nucleus
Nucleus
Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus.
The Cell: Organelles and is released from the
bone
Bone
Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy.
Bones: Structure and Types marrow to become a macrophage in the tissues.
Dendritic cells Dendritic cells Specialized cells of the hematopoietic system that have branch-like extensions. They are found throughout the lymphatic system, and in non-lymphoid tissues such as skin and the epithelia of the intestinal, respiratory, and reproductive tracts. They trap and process antigens, and present them to T-cells, thereby stimulating cell-mediated immunity. They are different from the non-hematopoietic follicular dendritic cells, which have a similar morphology and immune system function, but with respect to humoral immunity (antibody production). Skin: Structure and Functions release Release Release of a virus from the host cell following virus assembly and maturation. Egress can occur by host cell lysis, exocytosis, or budding through the plasma membrane. Virology IL-12, which activates CD4 Th1 Th1 A subset of helper-inducer T-lymphocytes which synthesize and secrete interleukin-2; interferon-gamma; and interleukin-12. Due to their ability to kill antigen-presenting cells and their lymphokine-mediated effector activity, th1 cells are associated with vigorous delayed-type hypersensitivity reactions. T cells: Types and Functions cells. These Th1 Th1 A subset of helper-inducer T-lymphocytes which synthesize and secrete interleukin-2; interferon-gamma; and interleukin-12. Due to their ability to kill antigen-presenting cells and their lymphokine-mediated effector activity, th1 cells are associated with vigorous delayed-type hypersensitivity reactions. T cells: Types and Functions cells produce IL-2, stimulating production of more Th1 Th1 A subset of helper-inducer T-lymphocytes which synthesize and secrete interleukin-2; interferon-gamma; and interleukin-12. Due to their ability to kill antigen-presenting cells and their lymphokine-mediated effector activity, th1 cells are associated with vigorous delayed-type hypersensitivity reactions. T cells: Types and Functions T-cell subsets. Th1 Th1 A subset of helper-inducer T-lymphocytes which synthesize and secrete interleukin-2; interferon-gamma; and interleukin-12. Due to their ability to kill antigen-presenting cells and their lymphokine-mediated effector activity, th1 cells are associated with vigorous delayed-type hypersensitivity reactions. T cells: Types and Functions cells also release Release Release of a virus from the host cell following virus assembly and maturation. Egress can occur by host cell lysis, exocytosis, or budding through the plasma membrane. Virology IFN IFN Interferon (IFN) is a cytokine with antiviral properties (it interferes with viral infections) and various roles in immunoregulation. The different types are type I IFN (IFN-É‘ and IFN-β), type II IFN (IFN-ÉŁ), and type III IFN (IFN-Ć›). Interferons-Îł, which activates macrophages and activates fibroblasts Fibroblasts Connective tissue cells which secrete an extracellular matrix rich in collagen and other macromolecules. Sarcoidosis to cause angiogenesis Angiogenesis Bartonella and fibrosis Fibrosis Any pathological condition where fibrous connective tissue invades any organ, usually as a consequence of inflammation or other injury. Bronchiolitis Obliterans. If these macrophages are persistently stimulated by pathogens, such as Mycobacterium Mycobacterium Mycobacterium is a genus of the family Mycobacteriaceae in the phylum Actinobacteria. Mycobacteria comprise more than 150 species of facultative intracellular bacilli that are mostly obligate aerobes. Mycobacteria are responsible for multiple human infections including serious diseases, such as tuberculosis (M. tuberculosis), leprosy (M. leprae), and M. avium complex infections. Mycobacterium and Schistosoma Schistosoma Schistosomiasis is an infection caused by Schistosoma, a trematode. Schistosomiasis occurs in developing countries with poor sanitation. Freshwater snails are the intermediate host and are transmitted to humans through skin contact with contaminated fresh water. The clinical presentation occurs as a result of the host’s immune response to antigens from the eggs. Schistosoma/Schistosomiasis, granulomas Granulomas A relatively small nodular inflammatory lesion containing grouped mononuclear phagocytes, caused by infectious and noninfectious agents. Sarcoidosis are formed.
Image by Lecturio.It is important to note that follicular dendritic cells Follicular dendritic cells Non-hematopoietic cells, with extensive dendritic processes, found in the primary and secondary follicles of lymphoid tissue (the B cell zones). They are different from conventional dendritic cells associated with T-cells. They are derived from mesenchymal stem cells and are negative for class II mhc antigen and do not process or present antigen like the conventional dendritic cells do. Instead, follicular dendritic cells have fc receptors and C3b receptors that hold antigen in the form of antigen-antibody complexes on their surfaces for long periods for recognition by B-cells. MALT Lymphoma are completely unrelated to dendritic cells Dendritic cells Specialized cells of the hematopoietic system that have branch-like extensions. They are found throughout the lymphatic system, and in non-lymphoid tissues such as skin and the epithelia of the intestinal, respiratory, and reproductive tracts. They trap and process antigens, and present them to T-cells, thereby stimulating cell-mediated immunity. They are different from the non-hematopoietic follicular dendritic cells, which have a similar morphology and immune system function, but with respect to humoral immunity (antibody production). Skin: Structure and Functions in lineage and function.
Follicular dendritic cells Follicular dendritic cells Non-hematopoietic cells, with extensive dendritic processes, found in the primary and secondary follicles of lymphoid tissue (the B cell zones). They are different from conventional dendritic cells associated with T-cells. They are derived from mesenchymal stem cells and are negative for class II mhc antigen and do not process or present antigen like the conventional dendritic cells do. Instead, follicular dendritic cells have fc receptors and C3b receptors that hold antigen in the form of antigen-antibody complexes on their surfaces for long periods for recognition by B-cells. MALT Lymphoma:
Dendritic cells Dendritic cells Specialized cells of the hematopoietic system that have branch-like extensions. They are found throughout the lymphatic system, and in non-lymphoid tissues such as skin and the epithelia of the intestinal, respiratory, and reproductive tracts. They trap and process antigens, and present them to T-cells, thereby stimulating cell-mediated immunity. They are different from the non-hematopoietic follicular dendritic cells, which have a similar morphology and immune system function, but with respect to humoral immunity (antibody production). Skin: Structure and Functions | Follicular dendritic cells Follicular dendritic cells Non-hematopoietic cells, with extensive dendritic processes, found in the primary and secondary follicles of lymphoid tissue (the B cell zones). They are different from conventional dendritic cells associated with T-cells. They are derived from mesenchymal stem cells and are negative for class II mhc antigen and do not process or present antigen like the conventional dendritic cells do. Instead, follicular dendritic cells have fc receptors and C3b receptors that hold antigen in the form of antigen-antibody complexes on their surfaces for long periods for recognition by B-cells. MALT Lymphoma | |
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Origin | Derived from hematopoietic stem cells Hematopoietic stem cells Progenitor cells from which all blood cells derived. They are found primarily in the bone marrow and also in small numbers in the peripheral blood. Bone Marrow: Composition and Hematopoiesis | Derived from mesenchymal stem cells |
Sites | Present throughout the body | Present only in germinal centers of secondary lymphoid tissues |
MHC class and costimulatory molecules | Possess MHC II and costimulatory (e.g., B7) molecules | Lack MHC II and costimulatory molecules |
Functions |
|
|
Eosinophil and basophil
Both are
granulocytes
Granulocytes
Leukocytes with abundant granules in the cytoplasm. They are divided into three groups according to the staining properties of the granules: neutrophilic, eosinophilic, and basophilic. Mature granulocytes are the neutrophils; eosinophils; and basophils.
White Myeloid Cells: Histology, with eosinophils possessing a bilobed
nucleus
Nucleus
Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus.
The Cell: Organelles and dark pink granules and basophils having a bilobed or trilobed
nucleus
Nucleus
Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus.
The Cell: Organelles, and dark blue granules.
Antigen Antigen Substances that are recognized by the immune system and induce an immune reaction. Vaccination-presenting cells (such as dendritic cells Dendritic cells Specialized cells of the hematopoietic system that have branch-like extensions. They are found throughout the lymphatic system, and in non-lymphoid tissues such as skin and the epithelia of the intestinal, respiratory, and reproductive tracts. They trap and process antigens, and present them to T-cells, thereby stimulating cell-mediated immunity. They are different from the non-hematopoietic follicular dendritic cells, which have a similar morphology and immune system function, but with respect to humoral immunity (antibody production). Skin: Structure and Functions and macrophages) detect, process, and present the antigens to T cells T cells Lymphocytes responsible for cell-mediated immunity. Two types have been identified – cytotoxic (t-lymphocytes, cytotoxic) and helper T-lymphocytes (t-lymphocytes, helper-inducer). They are formed when lymphocytes circulate through the thymus gland and differentiate to thymocytes. When exposed to an antigen, they divide rapidly and produce large numbers of new T cells sensitized to that antigen. T cells: Types and Functions, allowing adaptive immunity to recognize and mount a response every time the pathogen is encountered (immunologic memory Memory Complex mental function having four distinct phases: (1) memorizing or learning, (2) retention, (3) recall, and (4) recognition. Clinically, it is usually subdivided into immediate, recent, and remote memory. Psychiatric Assessment).
Structures of MHC I and MHC II:
MHC I has 1 short and 1 long chain (ɑ chain with 3 domains: ɑ1, ɑ2, and ɑ3), associated with the β₂-microglobulin. MHC II has 2 ɑ and 2 β chains. The peptide
antigen
Antigen
Substances that are recognized by the immune system and induce an immune reaction.
Vaccination goes to the
antigen
Antigen
Substances that are recognized by the immune system and induce an immune reaction.
Vaccination-binding cleft.
MHC: major histocompatibility complex
Routes of
antigen
Antigen
Substances that are recognized by the immune system and induce an immune reaction.
Vaccination
presentation
Presentation
The position or orientation of the fetus at near term or during obstetric labor, determined by its relation to the spine of the mother and the birth canal. The normal position is a vertical, cephalic presentation with the fetal vertex flexed on the neck.
Normal and Abnormal Labor by MHC class I and II molecules:
In class I
antigen
Antigen
Substances that are recognized by the immune system and induce an immune reaction.
Vaccination
presentation
Presentation
The position or orientation of the fetus at near term or during obstetric labor, determined by its relation to the spine of the mother and the birth canal. The normal position is a vertical, cephalic presentation with the fetal vertex flexed on the neck.
Normal and Abnormal Labor (left), proteasomes degrade endogenous antigens or
proteins
Proteins
Linear polypeptides that are synthesized on ribosomes and may be further modified, crosslinked, cleaved, or assembled into complex proteins with several subunits. The specific sequence of amino acids determines the shape the polypeptide will take, during protein folding, and the function of the protein.
Energy Homeostasis (within the cell) into peptides. Peptide fragments are transported (via transporter associated with
antigen
Antigen
Substances that are recognized by the immune system and induce an immune reaction.
Vaccination processing (TAP)) to the ER, where they are further trimmed by
aminopeptidases
Aminopeptidases
A subclass of exopeptidases that act on the free n terminus end of a polypeptide liberating a single amino acid residue.
Proteins and Peptides and loaded onto the MHC class I molecule. MHC class I–loaded complexes go to the Golgi apparatus for posttranslational modification. Then the complexes are transported to the cell surface, where they are presented to CD8+
T cells
T cells
Lymphocytes responsible for cell-mediated immunity. Two types have been identified – cytotoxic (t-lymphocytes, cytotoxic) and helper T-lymphocytes (t-lymphocytes, helper-inducer). They are formed when lymphocytes circulate through the thymus gland and differentiate to thymocytes. When exposed to an antigen, they divide rapidly and produce large numbers of new T cells sensitized to that antigen.
T cells: Types and Functions.
IN class II
antigen
Antigen
Substances that are recognized by the immune system and induce an immune reaction.
Vaccination
presentation
Presentation
The position or orientation of the fetus at near term or during obstetric labor, determined by its relation to the spine of the mother and the birth canal. The normal position is a vertical, cephalic presentation with the fetal vertex flexed on the neck.
Normal and Abnormal Labor (right), extracellular/exogenous antigens are taken up within phagosomes by
antigen
Antigen
Substances that are recognized by the immune system and induce an immune reaction.
Vaccination-presenting cells. The phagosomes then fuse with proteolytic enzyme-filled
lysosomes
Lysosomes
A class of morphologically heterogeneous cytoplasmic particles in animal and plant tissues characterized by their content of hydrolytic enzymes and the structure-linked latency of these enzymes. The intracellular functions of lysosomes depend on their lytic potential. The single unit membrane of the lysosome acts as a barrier between the enzymes enclosed in the lysosome and the external substrate. The activity of the enzymes contained in lysosomes is limited or nil unless the vesicle in which they are enclosed is ruptured or undergoes membrane fusion.
The Cell: Organelles. This results in the breakdown of phagocytosed
proteins
Proteins
Linear polypeptides that are synthesized on ribosomes and may be further modified, crosslinked, cleaved, or assembled into complex proteins with several subunits. The specific sequence of amino acids determines the shape the polypeptide will take, during protein folding, and the function of the protein.
Energy Homeostasis into small peptides. Meanwhile, in the
endoplasmic reticulum
Endoplasmic reticulum
A system of cisternae in the cytoplasm of many cells. In places the endoplasmic reticulum is continuous with the plasma membrane (cell membrane) or outer membrane of the nuclear envelope. If the outer surfaces of the endoplasmic reticulum membranes are coated with ribosomes, the endoplasmic reticulum is said to be rough-surfaced; otherwise it is said to be smooth-surfaced.
The Cell: Organelles (ER), new MHC class II molecules are synthesized. These molecules have the invariant chain (pink structure in the right image, marked Ii), which binds the
antigen
Antigen
Substances that are recognized by the immune system and induce an immune reaction.
Vaccination-binding cleft. With the cleft occluded (by the invariant chain), ER-resident peptides cannot
bind
BIND
Hyperbilirubinemia of the Newborn. The invariant chain directs the MHC II complex to the acidified
endosome
Endosome
Cytoplasmic vesicles formed when coated vesicles shed their clathrin coat. Endosomes internalize macromolecules bound by receptors on the cell surface.
Hepatitis C Virus (where
antigen
Antigen
Substances that are recognized by the immune system and induce an immune reaction.
Vaccination peptides are) as it exits from the ER. When MHC II complexes are delivered to the
endosome
Endosome
Cytoplasmic vesicles formed when coated vesicles shed their clathrin coat. Endosomes internalize macromolecules bound by receptors on the cell surface.
Hepatitis C Virus, the invariant chain is released, allowing loading of
antigen
Antigen
Substances that are recognized by the immune system and induce an immune reaction.
Vaccination peptides (chaperoned by a protein, HLA-
DM
DM
Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance.
Diabetes Mellitus) onto the MHC class II molecules. Once loaded, the formed
antigen
Antigen
Substances that are recognized by the immune system and induce an immune reaction.
Vaccination peptide-MHC class II complexes are brought to the cell surface, ready to present the
antigen
Antigen
Substances that are recognized by the immune system and induce an immune reaction.
Vaccination to CD4+
T cells
T cells
Lymphocytes responsible for cell-mediated immunity. Two types have been identified – cytotoxic (t-lymphocytes, cytotoxic) and helper T-lymphocytes (t-lymphocytes, helper-inducer). They are formed when lymphocytes circulate through the thymus gland and differentiate to thymocytes. When exposed to an antigen, they divide rapidly and produce large numbers of new T cells sensitized to that antigen.
T cells: Types and Functions.
Ii: MHC class II–associated invariant chain
MIIC: MHC class II compartment
Antigen
Antigen
Substances that are recognized by the immune system and induce an immune reaction.
Vaccination-presenting–cell and T-cell interaction:
Antigen
Antigen
Substances that are recognized by the immune system and induce an immune reaction.
Vaccination-presenting cell interacts with T cell via signal 1 (T-cell
receptor
Receptor
Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell.
Receptors binding the cognate
antigen
Antigen
Substances that are recognized by the immune system and induce an immune reaction.
Vaccination presented by MHC molecule in the
APC
APC
A polyposis syndrome due to an autosomal dominant mutation of the apc genes on chromosome 5. The syndrome is characterized by the development of hundreds of adenomatous polyps in the colon and rectum of affected individuals by early adulthood.
Familial Adenomatous Polyposis) and signal 2 (
costimulatory molecule
Costimulatory molecule
T cells: Types and Functions interaction between
APC
APC
A polyposis syndrome due to an autosomal dominant mutation of the apc genes on chromosome 5. The syndrome is characterized by the development of hundreds of adenomatous polyps in the colon and rectum of affected individuals by early adulthood.
Familial Adenomatous Polyposis and T cell). With the proper
antigen
Antigen
Substances that are recognized by the immune system and induce an immune reaction.
Vaccination
presentation
Presentation
The position or orientation of the fetus at near term or during obstetric labor, determined by its relation to the spine of the mother and the birth canal. The normal position is a vertical, cephalic presentation with the fetal vertex flexed on the neck.
Normal and Abnormal Labor, the mature T cell becomes activated.
MHC I | MHC II | |
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Loci | HLA-A HLA-A Polymorphic class I human histocompatibility (HLA) surface antigens present on almost all nucleated cells. At least 20 antigens have been identified which are encoded by the a locus of multiple alleles on chromosome 6. They serve as targets for t-cell cytolytic responses and are involved with acceptance or rejection of tissue/organ grafts. Organ Transplantation, HLA-B HLA-B Class I human histocompatibility (HLA) surface antigens encoded by more than 30 detectable alleles on locus B of the HLA complex, the most polymorphic of all the HLA specificities. Several of these antigens (e.g., hla-b27, -b7, -b8) are strongly associated with predisposition to rheumatoid and other autoimmune disorders. Like other class I HLA determinants, they are involved in the cellular immune reactivity of cytolytic T lymphocytes. Organ Transplantation, HLA-C HLA-C Class I human histocompatibility (HLA) antigens encoded by a small cluster of structural genes at the c locus on chromosome 6. They have significantly lower immunogenicity than the hla-a and -b determinants and are therefore of minor importance in donor/recipient crossmatching. Their primary role is their high-risk association with certain disease manifestations (e.g., spondyloarthritis, psoriasis, multiple myeloma). Organ Transplantation | HLA-DP, HLA-DQ, HLA-DR |
Binding | CD8 T cell | CD4 T cell |
Distribution | All nucleated cells (none on RBCs RBCs Erythrocytes, or red blood cells (RBCs), are the most abundant cells in the blood. While erythrocytes in the fetus are initially produced in the yolk sac then the liver, the bone marrow eventually becomes the main site of production. Erythrocytes: Histology) | Antigen Antigen Substances that are recognized by the immune system and induce an immune reaction. Vaccination-presenting cells |
Role | Present endogenous antigens to CD8+ T cells T cells Lymphocytes responsible for cell-mediated immunity. Two types have been identified – cytotoxic (t-lymphocytes, cytotoxic) and helper T-lymphocytes (t-lymphocytes, helper-inducer). They are formed when lymphocytes circulate through the thymus gland and differentiate to thymocytes. When exposed to an antigen, they divide rapidly and produce large numbers of new T cells sensitized to that antigen. T cells: Types and Functions (cytolytic) | Present exogenous antigens to CD4+ T cells T cells Lymphocytes responsible for cell-mediated immunity. Two types have been identified – cytotoxic (t-lymphocytes, cytotoxic) and helper T-lymphocytes (t-lymphocytes, helper-inducer). They are formed when lymphocytes circulate through the thymus gland and differentiate to thymocytes. When exposed to an antigen, they divide rapidly and produce large numbers of new T cells sensitized to that antigen. T cells: Types and Functions |
Structure |
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2 chains of equal length (2 ɑ, 2 β) |
Associated protein | β₂-microglobulin | Invariant chain |
Antigen Antigen Substances that are recognized by the immune system and induce an immune reaction. Vaccination loading | Loading of antigen Antigen Substances that are recognized by the immune system and induce an immune reaction. Vaccination peptide onto MHC I in ER (delivered via TAP) | Loading of antigen Antigen Substances that are recognized by the immune system and induce an immune reaction. Vaccination peptide onto MHC II in the acidified phagolysosome Phagolysosome Chédiak-Higashi Syndrome after release Release Release of a virus from the host cell following virus assembly and maturation. Egress can occur by host cell lysis, exocytosis, or budding through the plasma membrane. Virology of invariant chain |
The HLA region encodes several molecules that perform key functions in the immune system Immune system The body’s defense mechanism against foreign organisms or substances and deviant native cells. It includes the humoral immune response and the cell-mediated response and consists of a complex of interrelated cellular, molecular, and genetic components. Primary Lymphatic Organs. There is a robust association between the HLA region and several diseases.
HLA subtype | Condition(s) | Mnemonics |
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A3 | Hemochromatosis Hemochromatosis A disorder of iron metabolism characterized by a triad of hemosiderosis; liver cirrhosis; and diabetes mellitus. It is caused by massive iron deposits in parenchymal cells that may develop after a prolonged increase of iron absorption. Hereditary Hemochromatosis | HA3mochromatosis Fe3 ( iron Iron A metallic element with atomic symbol fe, atomic number 26, and atomic weight 55. 85. It is an essential constituent of hemoglobins; cytochromes; and iron-binding proteins. It plays a role in cellular redox reactions and in the transport of oxygen. Trace Elements = hemochromatosis Hemochromatosis A disorder of iron metabolism characterized by a triad of hemosiderosis; liver cirrhosis; and diabetes mellitus. It is caused by massive iron deposits in parenchymal cells that may develop after a prolonged increase of iron absorption. Hereditary Hemochromatosis), A3 |
B8 |
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Don’t B l8, Dr. Addison, or you’ll send my patient to the grave! |
B27 |
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PAIR |
C | Psoriasis Psoriasis Psoriasis is a common T-cell-mediated inflammatory skin condition. The etiology is unknown, but is thought to be due to genetic inheritance and environmental triggers. There are 4 major subtypes, with the most common form being chronic plaque psoriasis. Psoriasis | “C-riasis” |
DQ2/DQ8 | Celiac disease Celiac disease Celiac disease (also known as celiac sprue or gluten enteropathy) is an autoimmune reaction to gliadin, which is a component of gluten. Celiac disease is closely associated with HLA-DQ2 and HLA-DQ8. The immune response is localized to the proximal small intestine and causes the characteristic histologic findings of villous atrophy, crypt hyperplasia, and intraepithelial lymphocytosis. Celiac Disease | I 8 2 much gluten Gluten Prolamins in the endosperm of seeds from the triticeae tribe which includes species of wheat; barley; and rye. Celiac Disease at Dairy Queen (DQ2/8; gluten Gluten Prolamins in the endosperm of seeds from the triticeae tribe which includes species of wheat; barley; and rye. Celiac Disease = celiac disease Celiac disease Celiac disease (also known as celiac sprue or gluten enteropathy) is an autoimmune reaction to gliadin, which is a component of gluten. Celiac disease is closely associated with HLA-DQ2 and HLA-DQ8. The immune response is localized to the proximal small intestine and causes the characteristic histologic findings of villous atrophy, crypt hyperplasia, and intraepithelial lymphocytosis. Celiac Disease) |
DR2 |
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DR3 |
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DR4 |
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DR5 | Hashimoto’s thyroiditis Thyroiditis Thyroiditis is a catchall term used to describe a variety of conditions that have inflammation of the thyroid gland in common. It includes pathologies that cause an acute illness with severe thyroid pain (e.g., subacute thyroiditis and infectious thyroiditis) as well as conditions in which there is no clinically evident inflammation and the manifestations primarily reflect thyroid dysfunction or a goiter (e.g., painless thyroiditis and fibrous Riedel’s thyroiditis). Thyroiditis | Dr. Hashimoto is odd (odd numbers 3, 5) |
DR7 | Steroid-responsive nephrotic syndrome Nephrotic syndrome Nephrotic syndrome is characterized by severe proteinuria, hypoalbuminemia, and peripheral edema. In contrast, the nephritic syndromes present with hematuria, variable loss of renal function, and hypertension, although there is sometimes overlap of > 1 glomerular disease in the same individual. Nephrotic Syndrome | 7, “pee in heaven” (nephrotic) |