title: The specificity of T-cell helper factor in man.
abstract: Supernates of human T cells stimulated with TT antigen contain a factor that induces mitogenesis and immunoglobulin synthesis in autologous as well as allogeneic B cells. A fraction of the IgG produced has specificity against TT. The T-cell-derived LMF-TT eluted after albumin on Sephadex G 200 and did not contain immunoglobulin heavy chain determinants. LMF-TT was active on B cells from TT immune as well as TT- nonimmune individuals but in the latter instance the IgG secreted had no specificity against TT. B cells incubated with LMF-TT in the presence of a second antigen (DT) made IgG with specifity to that antigen provided the B-cell donor was immune to that second antigen. LMF-TT-containing supernates were depleted of TT antigen by Sephadex G 200 chromatography followed by passage over anti-TT immunosorbent columns. The antigen-free supernates were able to induce mitogenesis and IgG synthesis in B cells but the IgG produced failed to exhibit specificity against TT unless the TT antigen was readded to the B-cell cultures. The optimal concentration of LMF-TT (50 percent) inducing B-cell mitogenesis was different from the optimal concentration (20 percent) causing IgG synthesis by B cells. At low LMF concentrations (less than or equal 10 percent) addition of a second antigen to which the cell donor was immune caused an increase in the degree of B-cell mitogenesis. Submitogenic concentrations of LMF-TT (less than or equal to 5 percent) were still capable of inducingimmunoglobulin synthesis in B cells At these low concentrations of LMF-TT the proportion of anti-TT IgG over total IgG increased sharply. B cells from TT immune donors were separated on TT immunosorbent columns. Cells that bound to the column were more sensitive to the mitogenic and IgG synthetic effects of LMF-TT than unfractionated B cells. Thus, LMF is a nonspecific human T-cell helper factor which behaves like a polyclonal B-cell activator. However, in the presence of specific antigen (TT) the antigen-specific B cell is preferentially triggered by LMF. The experimental design of the present study does not rule out the additional presence of an antigen-specific helper factor in the supernates of TT-stimulated human T cells.
mesh_terms: D000917:Antibody Formation; D000921:Antibody-Producing Cells / Q000276:immunology; D000941:Antigens; D001402:B-Lymphocytes / Q000276:immunology; D004247:DNA / Q000096:biosynthesis; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007109:Immunity; D007074:Immunoglobulin G / Q000096:biosynthesis; D007164:Immunosorbents / Q000494:pharmacology; D008938:Mitosis; D013601:T-Lymphocytes / Q000276:immunology*; D013745:Tetanus Toxoid
chemical_list: D000941:Antigens; D007074:Immunoglobulin G; D007164:Immunosorbents; D013745:Tetanus Toxoid; D004247:DNA