Early expansion of secondary B cells after primary immunization with antigen complexed with IgE

Abstract

IgE antibodies have potent immunoregulatory effects in vivo, and mice immunized with IgE-antigen (IgE/Ag) complexes exhibit a several hundred-fold higher humoral Ag-specific response than mice immunized with non-complexed Ag. In vitro studies indicate that this is a result of efficient endocytosis of the IgE/Ag complexes via the low affinity receptor for IgE (CD23) on B cells, leading to efficient antigen presentation to T cells. Previous studies of IgE-induced Ab responses in vivo have only measured serum responses. The authors have now studied the up-regulated response as the number of IgG-, IgA- IgE- and IgM-secreting single B cells in spleen, lymph nodes and bone marrow of mice immunized with IgE-anti-TNP + BSA-TNP (2.4.6- trinitrophenylated bovine serum albumin). IgE and Ag induced a greater than 500-fold increase of specific IgG-secreting spleen cells with the peak of the response 6 days after primary immunization. The response of other Ab isotypes and the response in other lymphoid organs was marginal. The rapid increase in the number of IgG-secreting cells in the spleen suggests that IgE/Ag complexes induce a secondary type of antibody response without requirement for conventional priming.