A spleen cell derived factor imparts resistance to NK cell mediated lysis in a mouse lymphoma cell line

The effect of interleukin-2 (IL-2) preparations on the susceptibility of YAC cells to mouse natural killer (NK) cells was examined. Crude IL-2 preparations induced a significant decrease in the susceptibility of YAC cells. Highly purified IL-2 preparations, however, did not have a similar effect. Since the IL-2 preparations used in this study were purified from the culture supernatant of Con A activated spleen cells (Con A Sup.), our results indicated the presence in Con A Sup. of a lysis resistance inducing factor (LRIF), distinct from IL-2. We were able to purify LRIF from Con A Sup. by preparative isoelectric focusing and determined its isoelectric pH to be 4.8.