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Introduction to the immune system
MHC class I and MHC class II molecules
B-cell activation and differentiation
Cell-mediated immunity of CD4 cells
Cell-mediated immunity of natural killer and CD8 cells
Somatic hypermutation and affinity maturation
Contracting the immune response and peripheral tolerance
B- and T-cell memory
Anergy, exhaustion, and clonal deletion
Type I hypersensitivity
Type II hypersensitivity
Type III hypersensitivity
Type IV hypersensitivity
Innate immune system
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The immune response is highly specific for each invader, and that’s because the cells of the adaptive immune response have unique receptors that can differentiate friendly bacteria from deadly pathogens by their unique parts - called antigens.
The key cells of the adaptive immune response are the lymphocytes - the B and T cells which have unique antigen receptors known as the B cell receptor or BCR and T cell receptor or TCR respectively.
Both B cells and T cells undergo a process called VDJ rearrangement to generate a massively diverse set of receptors.
B cells can further enhance the diversity of their BCR repertoire using a process called somatic hypermutation, and the result is that the cells that emerge will have a stronger and more specific response to the antigen - and this is called affinity maturation.
Now remember, that the B cell receptor is essentially an antibody except that it’s attached to the surface of the B cell.
And each B cell receptor or antibody has two general parts- the variable region which binds antigen and the constant region which determines the specific antibody class - IgM, IgG, IgA, IgD, or IgE.
When B cell receptors are initially created it’s done in the absence of antigen.
Somatic hypermutation only happens in activated B cells, and not in T cells.
This happens at sites where B cells are activated and T cells are also present- basically in germinal centers within lymph nodes and the spleen.
Somatic hypermutation and affinity maturation are two mechanisms by which the immune system can adapt to better recognize and neutralize pathogens. Somatic hypermutation is a cellular mechanism by which the immune system adapts to the new foreign elements that confront it (e.g. microbes), whereas affinity maturation refers to the process of increasing the specificity and strength of the interaction between an antibody and its target antigen to increase the effectiveness of the immune response.
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