Elaboration of lymphotoxin by cultured human peripheral blood leucocytes stimulated with dental-plaque deposits.

Leucocyte cultures from subjects with periodontal disease when stimulated by human dental-plaque deposit material, or phytohaemagglutinin, produce a soluble factor, lymphotoxin, which is cytotoxic for fibroblasts . The cytotoxic effect was determined from the degree of inhibition of incorporation of C-labelled L-leucine by cultures of human gingival or mouse L-fibroblasts exposed to supernatants from such cultures. Inhibition of protein synthesis by the fibroblasts was not due to either depletion of nutrients or direct toxicity of the antigenic dental-plaque material. Both plaque-stimulated leucocyte culture supernatants from clinically normal subjects and unstimulated leucocyte culture supernatants from subjects with periodontal disease were significantly less inhibitory than supernatants of plaque-stimulated leucocyte cultures from subjects with periodontal disease. This production of lymphotoxin by leucocytes stimulated with antigen(s) present in dental plaque-deposits may reflect a mechanism of tissue destruction by sensitized lymphocytes present in the tissues of subjects with periodontal disease.