UC Irvine

High levels of cytotoxic activity (lymphotoxin-like (LT) detectable on L-929 cells was obtained in serum-free culture supernatants when non-adherent murine splenic lymphocytes or nylon wool-enriched T cells were cultured on monolayers of mitogen- (PHA) coated allogeneic or xenogeneic stimulator cells in vitro. Levels of lytic activity were lower in supernatants obtained from splenocyte cultures containing glass-adherent cell populations. Although release of lytic activity was very rapid, reaching maximal levels by 6 to 10 hr, this activity was very unstable. The levels of toxic activity in 8-hr supernatants were 20 to 50 times the levels obtained when lymphocytes were cultured with various dosages of mitogen (PHA-P, Con A) alone, even after 5 days of incubation. This phenomenon was not unique to murine lymphoid cells, for similarly high levels of LT activity were found in supernatants from lymphoid cells obtained from several animal species activated in a similar fashion. These results indicate that lymphoid cells from several animal species are capable of rapidly releasing high levels of cell-lytic activity in vitro not previously noted, and provide a means for obtaining highly active supernatants for biochemical studies. Furthermore, the data suggest that rapid release of LT may depend upon the nature of the cellular activating stimulus involving interaction of the lymphocyte with both lectin and target cell surface.