Mitogenic proteins of pokeweed. I. Purification, characterization and mitogenic activity of two proteins from pokeweed (Phytolacca octandra).

Saline extracts from the roots of the pokeweed species. Phytolacca octandra were separated by ion-exchange chromatography into three fractions, Po-1, Po-2 and Po-3. Po-1 contained two monomeric proteins with molecular weights of 36,000 and 29,000 and these were partially purified by gel filtration. Po-2 was purified as a single polymeric protein composed of approximately ten 14,000 mol. wt polypeptides and is a new pokeweed mitogen. Po-3 was purified as a single polymeric protein composed of approximately four 31,000 mol. wt subunits, and apart from its polymeric structure closely resembles commercial pokeweed mitogen (PWM). Po-2 and Po-3 were mitogenic for unseparated human peripheral blood lymphocytes but the degree of mitogenic activity in Po-2 preparations was dependent on storage following purification. Purified B cells were not stimulated by either mitogen. Po-3 was a potent mitogen for T cells but preparations of Po-2 required storage before they stimulated T cells. Higher responses were observed in co-cultures of B and T cells than in separated B and T cell cultures. It is suggested that human B and T lymphocytes show synergy in their responses to Po-2 and Po-3.