Regulatory factors in human serum: effect on murine T cells

Effect of lymphocyte E rosette stimulatory and inhibitory factors from human serum on murine T cells was studied. It was shown that the stimulatory factor (a polypeptide, temperature sensitive, with a molecular weight about 20,000, isolated from healthy individuals) interacted, in vitro, with murine spleen T cell precursors and generated formation of Thy-1,2+ cells. The cells generated were also active in GvH reaction. The stimulatory factor induced, in vitro, formation of cortisone-resistant thymocytes. Unfractionated pool of spleen cells treated with the inhibitory factor (a beta-lipoprotein isolated from sera of humans with active pulmonary tuberculosis) showed lower number of Thy-1,2+ cells, and lower activity in GvH reaction. However, when the spleen cells were subsequently treated with the stimulatory factor, the initial number of Thy-1,2+ cells was restored. It was confirmed that the factors did not interact with the target cells in the presence of prostaglandin inhibitors.