Enhanced capture of extramembranous IgM and IgG on B cells in the NOD mouse--implications for immune complex trapping.
Binding of various antibody isotypes to B cells through either FcgammaRs or complement receptors has been attributed to play several roles, e.g. in immune complex (IC) transportation and regulation of B cell receptor signaling. We have revealed a novel B cell intrinsic receptor for IgM and IgG which is present in C57BL/6 (B6) mice and is more abundant in non-obese diabetic (NOD) mice. As a consequence, the level of extramembranous IgG monomers and IgM pentamers on peripheral blood B cells from NOD mice was significantly higher compared with B6 mice. The effect of this aberration was that all B cells in peripheral blood of (NOD.IgH(a) x B6(IgH(b)))F(1) mice carried both IgM allotypes on their surface. In addition, analysis of IC binding using IgG- or IgM-opsonized bacterial particles revealed a higher degree of binding in NOD mice compared with B6. We hypothesize that this novel Ig-binding receptor is part of the normal immune system function. The aberrant function in the NOD mouse could contribute to the development of Type 1 diabetes by altering normal B cell functions such as activation, IC transportation and B cell homeostasis.
Ekici
Rifat
R
Department of Clinical Microbiology, Division of Immunology, Umeå University, SE-901 87 Umeå, Sweden.
Sundström
Mia
M
Thay
Bernard
B
Lejon
Kristina
K
D000818:Animals; D000936:Antigen-Antibody Complex / Q000276:immunology* / Q000378:metabolism; D001402:B-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D007074:Immunoglobulin G / Q000276:immunology* / Q000378:metabolism; D007075:Immunoglobulin M / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D016688:Mice, Inbred NOD; D011947:Receptors, Antigen, B-Cell / Q000276:immunology* / Q000378:metabolism
D000936:Antigen-Antibody Complex; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D011947:Receptors, Antigen, B-Cell