Expression of LFA-1 adhesion molecules on cisplatin-treated macrophages.

Appropriately activated mononuclear phagocytes mediate contact-dependent tumoricidal activity. Adhesion structures involved in contact-dependent tumor cytotoxicity have not been defined. The present study was aimed at identifying the adhesion structure involved in the tumoricidal activity of cisplatin-activated murine peritoneal macrophages. Tumor cells of different histological origin were used as targets in a 24-h cytotoxicity assay. Anti-CD18 (LFA-1 beta) substantially inhibited macrophage cytotoxicity whereas anti-LFA-1 alpha marginally inhibited macrophage-mediated cytotoxicity. When combined together, almost complete inhibition of tumoricidal activity was observed. Activated macrophages showed augmented binding to target cells and anti-LFA MAb inhibited the binding of resting and activated macrophages to target cells. Cisplatin augmented the expression of LFA-1 alpha and beta integrins and LPS had no effect as assessed by immunoprecipitation. These results implicate that in cisplatin activated macrophages LFA-1 alpha and beta integrins are important molecules in contact-dependent tumoricidal activity.