title: Monoclonal antibodies to the human C3b/C4b receptor (CR1) enhance specific B cell differentiation.
abstract: The addition of monoclonal antibodies against the human C3b/C4b receptor (CR1) to cultures of peripheral blood lymphocytes in the presence of suboptimal amounts of TNP bound to polyacrylamide beads enhanced by 150 to 400% the specific anti-TNP response, as measured by a plaque-forming cell assay on day 7. Anti-CR1 antibodies similarly enhanced the anti-fluorescein antibody response. Enhancement only occurred in cultures performed in the presence of the relevant antigen. No enhancing effect on the anti-TNP response was observed on addition to cultures of monoclonal antibodies directed against other surface antigens of B cells or an anti-T cell antibody of the same subclass as that of anti-CR1 antibodies. Anti-CR1 antibodies alone did not induce nonspecific B cell proliferation and did not provide B cells with a first signal for proliferation in the presence of a source of B cell growth factors. Anti-CR1 antibodies did not enhance the nonspecific proliferative response of B cells to growth factors derived from PHA-stimulated T cells, semi-purified BCGF 20 KD, BCGF 50 KD, or recombinant IL 2 in the presence of anti-mu. In this respect, the effect of anti-CR1 antibodies differs from that of anti-CR2 antibodies which interact with early stages of B cell activation. In contrast, anti-CR1 antibodies enhanced specific differentiation of antigen-activated B cells in the absence of T cells when soluble T cell factors were provided. Similar results were obtained by using either of two sources of differentiation factors, the MLA-144 supernatant or a 30 to 15 KD fraction from PHA-stimulated T cells. These results indicate that triggering of CR1 on B cells positively regulates the specific antibody response to low doses of antigen by enhancing B cell differentiation whether T cell help is provided by intact T cells or by T cell-derived differentiation factors.
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology*; D000917:Antibody Formation; D001402:B-Lymphocytes / Q000276:immunology*; D002454:Cell Differentiation; D004306:Dose-Response Relationship, Immunologic; D006133:Growth Substances / Q000276:immunology; D006801:Humans; D007376:Interleukin-2 / Q000276:immunology; D015847:Interleukin-4; D008213:Lymphocyte Activation; D008222:Lymphokines / Q000276:immunology; D011951:Receptors, Complement / Q000276:immunology*; D017463:Receptors, Complement 3b; D013601:T-Lymphocytes / Q000276:immunology; D014301:Trinitrobenzenes / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D006133:Growth Substances; D007376:Interleukin-2; D008222:Lymphokines; D011951:Receptors, Complement; D017463:Receptors, Complement 3b; D014301:Trinitrobenzenes; D015847:Interleukin-4