Page 461 - Veterinary Immunology, 10th Edition

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FIG. 15.19 B cells in the germinal center undergo somatic
mutation as they respond to antigen presented by dendritic cells. If
the mutation enables them to bind antigen with increased affinity,
they will be stimulated to continue dividing. If, on the other hand, the
mutation reduces their antigen-binding affinity, they will undergo
apoptosis.

B Cell Subpopulations

In laboratory mice, there are two subpopulations of B cells that
develop from different precursor stem cells. These are called B1 and

B2 cells. B2 cells are conventional B cells that are central to the
adaptive antibody responses and are discussed in this chapter and
throughout the book. B2 cells appear late in neonatal life and are
the predominant population in adult bone marrow and produce

most of the body's IgG.
Mouse B1 cells originate from stem cells in the fetal liver or
omentum rather than the bone marrow. They are innate-like cells
that share some features with macrophages. They are, for example,

phagocytic and microbicidal (they produce reactive oxygen species)
+
and can present antigen to CD4 T cells. There are two
subpopulations of B1 cells termed B1a and B1b. B1a cells develop
exclusively in the neonate, are self-replenishing, and are responsible

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