Inhibition of lymphocyte response to mitogens by dipyridamole: preliminary findings.

It has been recently noted that dipyridamole (DP) may be involved in certain immunological reactions, in addition to its antiplatelet action. In the present investigation the mitogenic response of human lymphocytes from three groups of subjects to 3 different lectins was examined. In both the experimental group treated over a short period and in the controls a highly significant decrease in the mean lymphocyte response to all 3 mitogens was noted following 3 days of DP administration. The response remained low after an additional 3 days of treatment. Discontinuation of drug administration was followed by a significant increase in response to two mitogens, concanavalin A (Con A) and pokeweed mitogen (PWM). The response to phytohaemagglutinin (PHA) extent only increased to a small, non-significant. No change in the mean mitogenic response was detected in the group undergoing long-term treatment. The mechanism by which DP alters lymphocyte activity is as yet unknown.