B Lymphocyte Memory: Role of Stromal Cell Complement and FcγRIIB Receptors

To dissect the influence of CD21/CD35 and FcγRIIB in antigen retention and humoral memory, we used an adoptive transfer model in which antigen-primed B and T lymphocytes were given to sublethally irradiated wild-type mice or mice deficient in CD21/CD35 (Cr2(−/−)) or FcγRIIB receptors (FcγRIIB(−/−)). Cr2(−/−) chimeras showed impaired memory as characterized by a decrease in antibody titer, reduced frequency of antibody secreting cells, an absence of affinity maturation, and significantly reduced recall response. The impaired memory in Cr2(−/−) chimeras corresponded with the reduced frequency of antigen-specific memory B cells. Interestingly, FcγRIIB(−/−) chimeras showed a differential phenotype with impaired splenic but normal bone marrow responses. These data suggest that CD21/CD35 on stroma, including follicular dendritic cells, is critical to the maintenance of long-term B lymphocyte memory.