Types – Hypersensitivity

by Peter Delves, PhD

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    So we’re going to look at each of these four different types, and I’ll explain to you exactly what’s involved in these different types of hypersensitivity reaction. So Type I - IgE mediated mast cell degranulation. So here we have a mast cell, and on the surface of mast cells are Fc receptors that are specific for the IgE class of antibody. This is in fact the high affinity IgE receptor that’s called FcεR1. So this will bind IgE antibodies by the Fc region of the antibody. That’s why it’s called an Fc receptor. And we all have mast cells sitting in our tissues that have IgE on their cell surface. And it doesn’t cause any problems at all. The problem arises, is if an antigen comes in which the IgE is specific for, and that antigen binds to the IgE. Because what happens then, is that the IgE antibodies on the surface of the mast cell get linked together; we use the term cross-linked. And if this substance is a completely innocuous substance, for example grass pollen, we refer to it as an allergen. It’s going to generate allergy. And the consequence of the IgE antibodies being linked together by the allergen is that the mast cells release their granules, they degranulate. Type II hypersensitivity is cytotoxic antibodies against cell surface antigen. So here we have a cell surface, with some antigens present on the cell surface, and antibodies are bound to those antigens. Sometimes the antibodies can be directly toxic to the cell. However, in most cases, other components of the immune response are required in order for these antibodies to actually damage the cell. So for example, the classical pathway of complement may become activated, leading to the production of the membrane attack complex. Or killer cells,...

    About the Lecture

    The lecture Types – Hypersensitivity by Peter Delves, PhD is from the course Hypersensitivity and Autoimmune Disease. It contains the following chapters:

    • Hypersensitivity - Type I
    • Hypersensitivity – Type II
    • Hypersensitivity – Type III
    • Hypersensitivity – Type IV

    Included Quiz Questions

    1. Type IV
    2. Type I
    3. Type II
    4. Type III
    5. Type V
    1. FcεRI
    2. pMHCII
    3. Cell surface antigen receptors
    4. CD5a
    5. CR
    1. Type II and Type III
    2. Type I and Type II
    3. Type I and Type IV
    4. Type II and Type IV
    5. Type I and Type III

    Author of lecture Types – Hypersensitivity

     Peter Delves, PhD

    Peter Delves, PhD

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