title: Carrier-directed anti-hapten responses by B-cell subsets.
abstract: The capacity of the trinitrophenyl (TNP) haptenic group, coupled to a series of chemically dissimilar carriers, to cross-stimulate putative T- dependent and T-independent murine B-cell subpepulations was determined by using an in vitro limiting dilution technique to generate primary IgM responses. It was found that TNP-Ficoll and TNP-dextran, two T- independent antigens with little or no polyclonal mitogenicity, stimulate the same population of anti-TNP precursors, which is distinct from the precursor population activated by TNP-bacterial lipopolysaccharide (LPS), a T-independent polyclonal mitogen, or TNP-horse erythrocytes (HRBC), a T-dependent antigen. On the other hand, TNP-LPS and TNP-HRBC activate the same precursor population, indicating that LPS can substitute for the T- cell signal in T-dependent B-cell responses, whereas nonmitogenic T- independent antigens cannot. However, the cumulative evidence from this and other laboratories strongly indicates that LPS and T-dependent antigens activate B cells by different mechanisms. Of particular interest, LPS is incapable of activating B cells responsive to weakly- or nonmitogenic T-independent antigens. Based on clonal burst size, T-dependent antigens are capable of inducing greater antigen-specific B-cell proliferation than T-independent antigens. However, TNP conjugates of Ficoll and dextran, which are relatively poor inducers of polyclonal B-cell activation, induced larger anti-TNP clones than did TNP-LPS, a strong polyclonal mitogen. The findings reinforce the evidence favoring existence of multiple B- cell subpopulations with distinctive activation pathways. They also strengthen the proposition that a given B-cell subset can be activated by more than one mechanism.
mesh_terms: D000818:Animals; D000917:Antibody Formation; D000937:Antigen-Antibody Reactions; D000941:Antigens; D001402:B-Lymphocytes / Q000276:immunology*; D002455:Cell Division / Q000187:drug effects; D003911:Dextrans / Q000276:immunology; D004306:Dose-Response Relationship, Immunologic; D000939:Epitopes; D004912:Erythrocytes / Q000276:immunology; D005362:Ficoll / Q000276:immunology; D006241:Haptens; D007075:Immunoglobulin M / Q000096:biosynthesis; D008070:Lipopolysaccharides / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D009578:Nitrobenzenes / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology; D013950:Thymus Gland / Q000276:immunology; D014301:Trinitrobenzenes / Q000276:immunology*
chemical_list: D000941:Antigens; D003911:Dextrans; D000939:Epitopes; D006241:Haptens; D007075:Immunoglobulin M; D008070:Lipopolysaccharides; D009578:Nitrobenzenes; D014301:Trinitrobenzenes; D005362:Ficoll