The rabbit B cell antigen receptor is non-covalently associated with unique heteromeric protein complexes: possible insights into the membrane IgM/IgD coexpression paradox.
We describe several proteins that are components of the rabbit B cell receptor complex. Two proteins (37 kDa and 42 kDa) were found in non-covalent association with IgM expressed on B cells from peripheral blood. These proteins were also immunoprecipitated by anti-B29 (Ig-beta) and anti-mb1 (Ig-alpha) monoclonal antibodies. As in the mouse and human, the IgM associated molecules were found as heteromeric structures with non-reduced apparent molecular weights of approximately 70-75 kDa. On rabbit B cells we also found these proteins in a 100-135 kDa complex which may represent trimeric or tetrameric structures. By Western blot, the 37 kDa protein was identified as rabbit Ig-beta (B29), suggesting that the 42 kDa protein is rabbit Ig-alpha. These data suggest that rabbit IgM is associated with both Ig-alpha/beta and Ig-(alpha beta)2 or alpha beta gamma complexes. When similar immunoprecipitation studies were performed on lysates made from B cells isolated from appendix follicles, we found two additional IgM associated protein complexes containing 34 kDa and 36 kDa proteins.
Fitts
M G
MG
Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
Metzger
D W
DW
Hendershot
L M
LM
Mage
R G
RG
D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D002462:Cell Membrane / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D007072:Immunoglobulin D / Q000276:immunology* / Q000378:metabolism; D007075:Immunoglobulin M / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D011817:Rabbits; D011940:Receptor Aggregation; D011947:Receptors, Antigen, B-Cell / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism
D007072:Immunoglobulin D; D007075:Immunoglobulin M; D011947:Receptors, Antigen, B-Cell