We have shown that during memory immune responses basophils are able to bind significant amounts of intact antigens on their surface. This binding is mediated by antigen-specific IgE molecules and high affinity IgE receptors on basophils. After re-exposure to antigens basophils become activated and constitute the main source of IL-4 and IL-6 in the spleen and bone marrow. Activated basophils markedly alter the phenotype of CD4+ T cells and play an important role in the development of memory immune responses as shown in models of immunization and infection. A memory type immune response predominates in transplantation, especially after acute rejections or in the setting of chronic transplant rejection. We hypothesize that basophils play an important role as modulators of humoral and cellular immune responses during acute and chronic transplant rejection and that activation of basophils is a good indicator for ongoing memory immune responses. These aspects will be investigated in vitro using MLR reactions, in mouse models of transplantation, and in patients after transplantation.
