Human lymphocyte mitogen of microbial origin and cell-cell interaction among leukocytes in response to the mitogen.

Abstract

Mitogenic substances on human peripheral blood mononuclear leukocytes were screened from culture filtrates of microorganisms newly isolated from soil and sea water by measuring [3H]-thymidine incorporation into the cells. Strong mitogenic activity was found in marine bacteria, particularly in marine vibrios. These mitogen samples exhibited neither hemagglutinating activity nor leukoagglutinating activity. They could scarcely stimulate murine lymphocytes. Cell-cell interaction among leukocyte subsets in response to a bacterial mitogen was investigated using the most powerfully mitogenic sample (culture filtrate of strain H 52-2). A slight decrease in the mitogen response was observed on depletion of plastic surface adherent cells. Separation of T and non-T cells from each other by erythrocyte-rosette sedimentation resulted in a markedly diminished mitogen response. Considerable restoration of the mitogen response was obtained when T cells were mixed with mitomycin C-treated adherent cells or mitomycin C-treated non-T lymphocytes, or when non-T lymphocytes were mixed with mitomycin C-treated T cells.