[Effect of gamma-ray irradiation, DNA and protein synthesis inhibitors on the generation of soluble suppressor factors by mononuclear leukocytes].

During a 4-days in vitro culturing period and without any antigenic or mitogenic stimulation, mononuclear leukocytes of normal human peripheral blood could release a soluble suppressor factor(s) which was able to suppress the one-way mixed lymphocyte reaction to an average degree of 45.3%. The generation of the aforementioned factor(s) was not affected by mitomycin C which is a DNA synthesis inhibitor, but was suppressed to a certain extent by protein synthesis inhibitors such as puromycin and cycloheximide. In addition, the factor(s) released by non-irradiated cells was more active than that released by irradiated counterparts, suggesting that the factor(s) was not a byproduct of cell death or metabolic toxic substances. The soluble suppressor factor(s) was found to be mainly generated by lymphocytes rather than by monocytes. However, the latter might, in some way, potentiate the generation of this factor(s).