Induction of DNA synthesis in normal human lymphocyte cultures by antigen-antibody complexes

Abstract

Antibodies were produced in various species against particulate (sheep red blood cells and Salmonella bacteria) or soluble (E. coli endotoxin, human serum albumin and mouse γ-globulin) antigens. Antibody mixed with the corresponding antigen stimulated DNA synthesis in normal human lymphocytes cultivated in vitro, whereas antibody alone or antigen alone had no or a negligible effect. The species origin of the antibody did not seem to influence the results. Maximal stimulation of DNA synthesis occurred after 5–6 days. Preformed antigen–antibody complexes were also stimulatory, whereas heat-aggregated γ-globulin had no effect. The addition of fresh complement did not increase DNA stimulation. The degree of stimulation of DNA synthesis after contact between lymphocytes from immunized individuals and the specific antigen was even further increased when humoral antibody was introduced.

The present findings suggest a mechanism by which non-committed lymphoid cells of host origin are activated by a small proportion of antibody-producing cells to participate in various cell-mediated immune reactions, in particular since it was found that lymphocytes stimulated by antigen–antibody complexes acquired the capacity to kill allogeneic and autochthonous fibroblasts.