Antigen conjugated to anti-CD23 antibodies is rapidly transported to splenic follicles by recirculating B cells.

IgE-antigen complexes, administered intravenously to mice, induce a several 100-fold higher specific antibody response than antigen alone. Additionally, in vivo activation and proliferation of specific CD4(+) T cells is enhanced. The mechanism behind these effects is thought to be that peripheral B cells capture IgE-antigen complexes via their low-affinity receptor for IgE, CD23, and rapidly transport them to splenic B cell follicles where an immune response is initiated. Here, we demonstrate that ovalbumin, covalently coupled to anti-CD23 antibodies and administered intravenously to mice, is also transported to splenic follicles and induces an enhanced primary antibody response. These effects are absent in CD23-deficient mice. No enhanced induction of immunological memory was observed. These findings extend previous observations regarding the in vivo role of CD23 and emphasize that recirculating B cells play an important role in antigen transport to the spleen.