Opsonic activity of guinea pig serum is reduced by in vivo administration of carcinogenic nitrosamines.

The administration of each of four carcinogenic nitrosamines to normal guinea pigs resulted in decreased opsonic activity of their sera but did not affect the capacity of their peritoneal macrophages to phagocytize particles opsonized with normal serum. Diphenylnitrosamine, a noncarcinogenic analogue, had no significant effect on opsonic or phagocytic activity.