title: Definition of conditions that enable antigen-specific activation of the majority of isolated trinitrophenol-binding B cells.
abstract: In an effort to further elucidate the early cellular events in generation of antibody responses, we have determined the requirements for antigen-specific initiation of the G0 to G1 transition by isolated trinitrophenol (TNP) -binding B lymphocytes. TNP-binding cells were isolated from normal B6D2F1 splenocyte populations using hapten affinity fractionation on disulfide-bonded TNP-gelatin-coated plates. Populations prepared in this way are greater than or equal to 96% immunoglobulin positive and 70-95% antigen binding. Isolated cells were cultured for 48 h in the presence of a variety of TNP conjugates including TNP-Brucella abortus (Ba), TNP-Ficoll, TNP-sheep erythrocytes (SRBC), TNP-human gamma globulin (HGG), or TNP-ovalbumin (OVA) before being harvested and subjected to acridine orange cell cycle analysis. As many as 80% of cells were in cycle by 48 h in response to TNP-Ba, a thymus-independent (TI1 antigen. A smaller proportion (congruent to 40%) were in cycle in response to TNP-Ficoll, a TI2 antigen. Significant activation was not detected in cultures challenged with the thymus-dependent immunogens TNP-SRBC, TNP-HGG, and TNP-OVA. Addition of interleukin 1 (IL-1), IL-2, B cell growth factor, and/or T cell-replacing factor to cultures did not facilitate responses to these immunogens, suggesting a requirement for antigen-specific T cell help for entry into cell cycle induced by thymus dependent antigens. Activation by TNP-Ba was antigen specific and independent of accessory cells, occurring with equal efficiency in bulk and single-cell cultures. Activation by TNP-Ba was inhibitable by anti-Fab and anti-mu antibodies, but not by anti-delta antibodies. Results indicate that activation of TNP-binding cells to enter cell cycle by TNP-Ba is independent of accessory cells and requires interaction of antigen with cell surface IgM. Exposure to thymus-dependent TNP-immunogens plus nonspecific helper factors is insufficient to cause entry of TNP-binding cells into cycle.
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology; D002003:Brucella abortus / Q000276:immunology; D000939:Epitopes; D005362:Ficoll / Q000276:immunology; D007072:Immunoglobulin D / Q000378:metabolism; D007075:Immunoglobulin M / Q000378:metabolism; D007163:Immunosorbent Techniques; D008213:Lymphocyte Activation; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D009578:Nitrobenzenes / Q000378:metabolism*; D010641:Phenotype; D011947:Receptors, Antigen, B-Cell / Q000378:metabolism; D014301:Trinitrobenzenes / Q000276:immunology / Q000378:metabolism*
chemical_list: D000939:Epitopes; D007072:Immunoglobulin D; D007075:Immunoglobulin M; D009578:Nitrobenzenes; D011947:Receptors, Antigen, B-Cell; D014301:Trinitrobenzenes; D005362:Ficoll