Immunologic Memory to Polysaccharide Antigens

Immunologic memory is the ability of the immune system to generate an enhanced antibody response against previously encountered antigens. The clonal selection theory of acquired immunity attributes immunologic memory to the formation of an expanded compartment of quiescent antigen-specific memory B cells that are capable of rapid activation upon secondary antigen encounter. Whereas protein antigens are known to elicit memory B cells, it is not known whether polysaccharide antigens do. Here we report that polysaccharide antigens elicit memory B cells that are phenotypically distinct from those elicited by protein antigens. We show that antigen affinity of the B cell receptor regulates the development of memory B cells and that antigen-specific IgG antibodies suppress recall responses against polysaccharides via a mechanism that does not depend on epitope masking or involve known Fey receptors