Specific T helper cells that activate B cells polyclonally. In vitro enrichment and cooperative function.

Abstract

C3H/HeJ T [thymus-derived] cells which specifically recognize B [bone marrow-derived] cell-surface antigens of the related, major histocompatibility complex-compatible C3H/Tif strain, can be substantially enriched in vitro by long-term exposure (2-6 wk) of primed lymph node cells to the relevant cellular antigens. These enriched T cells contain functional helper cells as demonstrated by their capacity to induce large numbers of Ig[immunoglobulin]-secreting plaque-forming cells (PFC) in cultures of antigenic B cells. The cooperative interaction results in activation of a large fraction of all splenic B cells, with consequent exponential growth and maturation to high rate secretion of IgM, IgG1 and IgG2, but not IgG3. The IgM PFC response includes antibody specificities to a number of different antigens and can be considered as polyclonal. The T helper cell-dependent B cell response is insensitive to inhibition by anti-.delta. antibodies, and in contrast with lipopolysaccharide-induced PFC responses, is only partially sensitive to the inhibitory effects of anti-.mu. antibodies. B cell activation to growth and maturation by helper T cells strictly required direct T cell recognition of antigens on the surface of responding B cells, leading us to the conclusions that if any soluble factors are generated in the collaborative process, they are either antigen specific or incompetent to initiate B cell growth.