Page 462 - Veterinary Immunology, 10th Edition

for most “natural” IgM in serum. They thus participate in innate
VetBooks.ir immunity. B1a cells express CD5, an adhesion and receptor

molecule. (CD5 is the receptor for CD72.) They recognize common
bacterial molecules such as phosphocholine as well molecules such

as immunoglobulins and DNA. They produce antibodies in a T-
independent manner. B1a cells also differ from conventional B2
cells in that they are found in the peritoneal and pleural cavities
and can renew themselves. B1b cells are distinguished from B1a

cells by lacking CD5. They are, however, required for protection
against several parasites and bacteria. B1b cells are produced
throughout adult life. Many of the IgA-producing cells in the
intestine originate from B1 cells. B1 cells have been identified in

humans, mice, rabbits, guinea pigs, pigs, sheep, and cattle. It is
unclear, however, whether the B1-B2 classification applies to all
these species.

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