For many years it has been known that the injection of antigen bound to an antibody leads to more than a 1000-fold increase in antigen specific antibody response. This observation holds true for IgE, which is dependent upon CD23 expression, as this enhancement is not present in mice deficient in CD23. It also has been shown that when mice are injected with IgE-antigen complexes also display an increase in antigen specific T cell proliferation. While there are published studies that demonstrate a role for B cell derived exosomes in the activation and proliferation of T cells, none have focused upon the potential role of CD23 as a molecular basis for this phenomenon, at least in the context of allergy and asthma. This thesis provides direct evidence that B cell-derived exosomes possess co-stimulatory molecules, including CD80 and CD86, which act in concert with CD23 to induce T cell proliferation, at least in vitro. This is due to, or enhanced by, the exosomal transfer of the antigen or peptide to T cells. Importantly, the antigen transfer is dependent upon the availability of IgE and the expression of CD23.