The effect of coumarin derivatives on the immunological system of man.

Peripheral blood lymphocyte mitogen responsiveness was studied in 12 normal and 51 cancer patients. One group of patients was treated with warfarin, the second group with coumarin. There was a significant increase in lymphocyte response to phytohaemagglutinin (PHA) following both drugs. This increase indicates that both agents are capable of activating lymphocytes and thus stimulating some immunological functions.