Lymphokine-like products of cultured tumour cells.

Supernatants from cultures of rat and guinea-pig tumour cells, guinea-pig fibroblasts and kidney cells, but not rat fibroblasts, inhibited the migration of peritoneal exudate macrophages in vitro. The inhibitory activity in tumour-cell supernatants differed from that of lymphokine in being heat stable (60 degrees, 3 hr) and dialysable, not inhibited by fucose and, in the case of guinea-pig line 1 tumour, not absorbed by an anti-lymphokine immunoabsorbent. Rat lymphokine and supernatants from four cultured rat tumours and, to a lesser extent, fibroblasts induced procoagulant activity in rat peritoneal exudate macrophages. The tumour procoagulant-inducing activity was heat stable and non-dialysable. Direct procoagulant activity was also found in rat lymphokine, fibroblast and tumour culture supernatants. This activity was partly or completely heat-labile but was non-dialysable.