Low responsiveness to immunization with immunoglobulin E antigen and immunoglobulin G antigen complexes in H-2A(b) mice

Immunoglobulin (Ig)E and IgG antibodies specific for 2,4,6-trinitrophenyl ( TNP) are able to enhance the carrier-specific antibody response to TNP-conj ugated soluble proteins such as bovine serum albumin (BSA). We have recentl y reported that mice carrying the MHC class II Ab molecule are low responde rs to immunization with IgE/antigen complexes and now show that H-2A(b) mic e are also low responders to IgG/antigen complexes. In addition, we found t hat spleen cells from naive low- and high-responder mice captured IgE/antig en complexes exclusively on B cells, and that the binding was completely in hibited by monoclonal antibodies (MoAbs) against the low-affinity receptor for IgE (Fc epsilon RII or CD23). The IgG/antigen complexes were targeted b oth to B cells and macrophages. The binding of IgG/antigen to B cells prima rily seemed to be dependent on the low-affinity receptor for IgG (Fc gamma RII or CD32), although some influence of complement receptor 2 (CR2 or CD21 ) was seen. Capture of IgG/antigen complexes on macrophages was partially b locked by MoAbs against Fc gamma RII/III. There was no difference in expres sion of Fc epsilon RII, Fc gamma RII/III, CR1, CR2, and CR3 between low- an d high-responder strains, thus excluding low levels of these FcRs and CRs a s a reason for low responsiveness in H-2Ab mice.