title: Murine B-cell subpopulations responsive to T-dependent and T-independent antigens.
abstract: Strain A/J mice made secondary indirect plaque-forming cell (PFC) responses to azobenzenearsonate (ABA) conjugates of giant keyhole limpet hemocyanin (KLH), a thymic-dependent antigen, but not to conjugates of Ficoll, a T-independent antigen. ABA-Ficoll was also unable to elicit a response in animals primed with ABA-KLH, which have an expanded anti-ABA memory cell pool. On the other hand, ABA-Ficoll rendered mice unresponsive to ABA-KLH when administered before priming or boosting with the T-dependent immunogen. Hence, the T-independent antigen was able to tolerize but unable to trigger B-memory cells responsive to the T-dependent antigen. A/J mice immunized with dinitrophenyl conjugates of Ficoll or bovine IgG (BGG) made vigorous IgM and IgG PFC responses. PFC responses to ABA-KLH and 2,4-dinitrophenyl (DNP)-BGG were abrogated by depleting mice of C3 with cobra venom factor, whereas the IgM and IgG PFC responses to DNP-Ficoll were unaffected. B lymphocytes were fractionated on the basis of receptors for C3 and the subpopulations were assayed for in vitro PFC responses to DNP-Ficoll. Very little response was obtained from complement receptor lymphocyte [CRL(+)] B cells, whereas CRL(-) cells were more responsive than unfractionated B cells. Both populations responded to a polyclonal B-cell mitogen (lipopolysaccharide). On the other hand, the in vitro PFC response to a T-dependent antigen (sheep erythrocytes) correlated with the presence of CRL(+) B cells in the cultures. However, a minor component of this response, sensitive to anti-Thy-1 serum, was made by CRL(-) B cells, indicating the existence of subpopulations of T-dependent B cells with different signalling requirements. The results suggest that most B cells responsive to T-dependent antigens possess receptors for C3 and that C3 plays an obligatory role in the response of these cells. A distinct subpopulation of B cells which lack C3 receptors respond to T-independent antigens. The precursors of PFC for the ABA epitope reside largely or exclusively in the CRL(+) compartment in A/J mice, whereas precursors for the DNP determinant are found in both compartments.
mesh_terms: D000818:Animals; D000917:Antibody Formation; D001391:Azo Compounds / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology*; D002352:Carrier Proteins / Q000276:immunology; D003176:Complement C3; D003165:Complement System Proteins; D005260:Female; D005362:Ficoll / Q000276:immunology; D006433:Hemocyanins / Q000276:immunology; D007156:Immunologic Memory; D051379:Mice; D008805:Mice, Inbred A; D011955:Receptors, Drug; D013154:Spleen / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*; D010132:p-Azobenzenearsonate / Q000276:immunology*
chemical_list: D001391:Azo Compounds; D002352:Carrier Proteins; D003176:Complement C3; D011955:Receptors, Drug; D005362:Ficoll; D010132:p-Azobenzenearsonate; D003165:Complement System Proteins; D006433:Hemocyanins