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Learning Objectives: Generation of Antigen-Specific B Cells

Reading Assignment: Janeway Chapter 4 pp 135-139 and 154-164 and Chapter 7 pp 247-250 and 258-265 or Parham Chapter 2 pp 47-49 and 52-61 and Chapter 4 pp 99-107

Supplementary Materials: Decker Tutorials  Antibody,   Antibody Genes,  B Cell Development ,  Flow Cytometry

B Cell Diversity refers to the large number of different antigen-binding sites available on antibodies/BCR . We know that the amount of diversity (the number of different antibody specificities) is very high, in the billions or higher. We also know that each individual B cell makes only one kind of light chain (κ or λ), every light chain with identical V_L regions. Each individual B cell makes antibodies containing identical V_H regions, but it can use that V_H with any of the C_H isotypes (μ , δ , γ , α and ε). The mechanism by which each developing B lymphocyte forms the genes for unique V_H and V_L or Vα and Vβ regions is called somatic recombination. It is a process that is unique to lymphocytes. As somatic recombination randomly produces V_H and V_L regions, some of these regions are able to bind self antigen. B cells producing self-specific BCR must be eliminated in a process called negative selection before the B cells are allowed to leave the bone marrow.

The developing B cell in the bone marrow first makes membrane IgM (monomer) and then membrane IgD. In the lymphoid organs following antigen contact, the B cell initially secretes IgM pentamer but, depending on signals from Th2 cells, can "switch" to secreting IgG, IgA or IgE (isotype switching).

When you finish Generation of Antigen-Specific B Cells, you should be able to