Isolation by electrofocusing of two lymphocyte mitogens produced by Staphylococcus aureus.

Staphylococcus aureus strain DA352, grown in a diffusate of Todd-Hewitt broth, produced two extracellular nondialyzable lymphocyte mitogens having isoelectric points of 5.5 to 5.7 and 8.6 to 9.0. The mitogens were separable from one another by isoelectric focusing and could be isolated free of detectable amounts of other staphylococcal products by ethanol precipitation followed by isoelectric focusing. Dose-response curves with both mitogens showed a maximum per cent transformation in the range (90%+) obtained with phytohemagglutinin (PHA), a decrease of transformation with excess mitogen, and, with decreasing concentrations, a slope somewhat less steep than that obtained with PHA. Incubation with undigested or pepsin-digested pooled human gamma globulin enhanced the activity of the basic mitogen.