Differentiation between various effects of cytotoxic fractions of lymphocyte culture medium

This paper describes the partial characterization of supernatants derived from mitogen stimulated lymphocytes by ammonium sulfate precipitation, ultrafiltration on Hollow-Fiber beakers and gelchromatography. Fractions from these purification procedures were tested on FL-target cells and the following target cell alterations were measured: RNA- and protein synthesis, 3H-TdR incorporation, cell number and lysis of target cells. Target cell alterations of control fractions from supernatants of non-stimulated lymphocytes, from culture medium and from FCS were compared to the effects of fractions from activated lymphocytes. 3H-TdR incorporation was not only inhibited by the fractions of activated lymphocyte cultures but also by fractions of various controls. Inhibition of 3H-TdR incorporation disappeared when control fractions were serially diluted. Only fractions of supernatant from activated lymphocytes could lyse target cells. It were the same fractions which still inhibited 3H-TdR incorporation of target cells after serial dilution and which showed stimulating effects on RNA synthesis. MW of fractions which were differentiated from control fractions with respect to target cell lysis were: 90,000, 45,000 and lower than 20,000 d.