Complement component 3 (C3) deficiency is the absence, reduction, or dysfunction of complement factor C3 and its fragments, C3a and C3b. Complement factors are key components of the innate immune system Innate immune system 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, pattern recognition receptors (PRRs) as well as circulating proteins, and immune cells that help eliminate the microbe. Innate Immunity: Phagocytes and Antigen Presentation. Reduced levels of C3b increase the probability Probability Probability is a mathematical tool used to study randomness and provide predictions about the likelihood of something happening. There are several basic rules of probability that can be used to help determine the probability of multiple events happening together, separately, or sequentially. Basics of Probability of developing infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease with encapsulated Encapsulated Klebsiella organisms (e.g., Pneumococcus, Haemophilus Haemophilus Haemophilus is a genus of Gram-negative coccobacilli, all of whose strains require at least 1 of 2 factors for growth (factor V [NAD] and factor X [heme]); therefore, it is most often isolated on chocolate agar, which can supply both factors. The pathogenic species are H. influenzae and H. ducreyi. Haemophilus influenza Influenza Influenza viruses are members of the Orthomyxoviridae family and the causative organisms of influenza, a highly contagious febrile respiratory disease. There are 3 primary influenza viruses (A, B, and C) and various subtypes, which are classified based on their virulent surface antigens, hemagglutinin (HA) and neuraminidase (NA). Influenza typically presents with a fever, myalgia, headache, and symptoms of an upper respiratory infection. Influenza Viruses/Influenza, Neisseria meningitidis Neisseria meningitidis A species of gram-negative, aerobic bacteria. It is a commensal and pathogen only of humans, and can be carried asymptomatically in the nasopharynx. When found in cerebrospinal fluid it is the causative agent of cerebrospinal meningitis. It is also found in venereal discharges and blood. There are at least 13 serogroups based on antigenic differences in the capsular polysaccharides; the ones causing most meningitis infections being a, b, c, y, and w-135. Each serogroup can be further classified by serotype, serosubtype, and immunotype. Neisseria), especially respiratory infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease, due to reduced opsonization. Individuals with C3 deficiencies are also more susceptible to type III hypersensitivity reactions because a reduced clearance of antigen-antibody C3b complexes from the circulation Circulation The movement of the blood as it is pumped through the cardiovascular system. ABCDE Assessment causes an increased risk of hypersensitivity reactions.
Last updated: 8 Mar, 2022
Complement component 3 (C3) deficiency is part of the larger category of complement deficiencies:
Membrane attack complex
Membrane attack complex
A product of complement activation cascade, regardless of the pathways, that forms transmembrane channels causing disruption of the target cell membrane and cell lysis. It is formed by the sequential assembly of terminal complement components (complement C5b; complement C6; complement C7; complement C8; and complement C9) into the target membrane. The resultant C5b-8-poly-c9 is the ‘membrane attack complex’ or MAC.
Type II Hypersensitivity Reaction (MAC) formation:
When the 1st protein in the complement series is activated (typically by an antibody locked onto an
antigen
Antigen
Substances that are recognized by the immune system and induce an immune reaction.
Vaccination), a domino effect is set into motion. Each component takes a turn in a precise chain of steps known as the complement cascade. The end
product
Product
A molecule created by the enzymatic reaction.
Basics of Enzymes is the cylindrical MAC, which inserts into and punctures a hole in the cell’s wall. With fluids and molecules flowing in and out, the cell swells and bursts.
Clinical testing directed by pattern of infection:
Management of patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with C3 deficiency centers on prevention of illness.