Suppression of lymphocyte activation by a factor produced by Mycoplasma arginini.

Mycoplasma arginini, when grown in broth or in cultures of human lymphoblast cell lines, inhibits activation of lymphocytes by allogeneic cells of mitogens. This inhibition can also be produced by cell free media obtained after the growth of this organism. Inhibition is not species specific and inhibits both B and T cell activation in the mouse. The inhibitory factor is required during the first 3 days of the mixed leukocyte culture, but has no effect on the latter phase of this reaction when thymidine uptake is greatest. The factor is stable to treatment at 60 degrees, but not 90 degrees, for 30 min.