EARLY EXPANSION OF SECONDARY B-CELLS AFTER PRIMARY IMMUNIZATION WITH ANTIGEN COMPLEXED WITH IGE

IgE antibodies have potent immunoregulatory effects in vivo, and mice immunized with IgE-antigen (IgE/Ag) complexes exhibit a several hundre d-fold higher humoral Ag-specific response than mice immunized with no n-complexed Ag, In vitro studies indicate that this is a result of eff icient endocytosis of the IgE/Ag complexes via the low-affinity recept or for IgE (CD23) on B cells, leading to efficient antigen presentatio n ro T cells. Previous studies of IgE-induced Ab responses in vivo hav e only measured serum responses. The authors have now studied the up-r egulated response as the number of IgG-, IgA-, IgE- and IgM-secreting single B cells in spleen, lymph nodes and bone marrow of mice immunize d with IgE-anti-TNP+BSA-TNP (2,4,6-trinitrophenylated bovine serum alb umin). 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 respo nse in other lymphoid organs was marginal. The rapid increase in the n umber of IgG-secreting cells in the spleen suggests that IgE/Ag comple xes induce a secondary type of antibody response without requirement f or conventional priming.