IgG diphtheria antitoxin responses from human tonsil lymphocytes induced by anti γ chain antibodies

Human tonsil lymphocytes were cultured for 24 hr with purified antibodies specific for human IgG heavy chain determinants (anti γ chain) and then cultured for 6.5 days in Marbrook tubes. IgG diphtheria antitoxin was measured in the culture supernatants by antigen binding radioimmunoassay. In cultures from eight tonsils, anti γ chain stimulated significant IgG antitoxin formation; in each case parallel cultures stimulated with toxoid gave good responses. The specificity of the antibody produced was established by showing that supernatants from cultures stimulated with anti γ chain will neutralize toxin. Total IgG in culture supernatants was measured by radioimmunoassay and it was found that cultures stimulated with anti γ chain generally produced less total IgG than unstimulated cultures. In time course experiments IgG antitoxin formation increased rapidly. after the 3rd day whereas over 50% of the total IgG was produced in the first 3 days. Evidence is presented which suggests that anti γ chain acts differently on different groups of B cells.