Page 458 - Veterinary Immunology, 10th Edition

years.) These antibodies provide immediate immunity to microbial
VetBooks.ir pathogens. The short-lived cells are found in the spleen and lymph

nodes soon after immunization. The long-lived plasma cells, in
contrast, accumulate in the bone marrow. These long-lived plasma

cells probably develop from a population of self-renewing, slowly
dividing memory B cells. These memory B cells require a functional
BCR to survive, suggesting that constant low-affinity antigen
binding keeps them alive. Thus cats immunized with killed

panleukopenia virus will continue to produce antibodies at low
levels for many years. The source of these antibodies is believed to
be the long-lived plasma cells stimulated to secrete antibodies by
exposure to PAMPs and T cell help.

If a second dose of antigen is given to a primed animal, it will
encounter large numbers of memory B cells, which respond in the
manner described previously for antigen-sensitive B cells (Fig.
15.18). As a result, a secondary immune response is much greater

than a primary immune response. The lag period is shorter since
more antibodies are produced, and they can be detected earlier. IgG
is also produced in preference to the IgM characteristic of the
primary response.

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