Lymphokines and thrombosis. I. Thrombocyte aggregating activity released by human lymphocytes stimulated with concanavalin-A.

Supernatants from Con-A stimulated human lymphocytes containing leucocyte migration inhibitory activity were measured for thrombocyte aggregation activity and for influence on thrombocyte rich plasma clot retraction and whole blood clot retraction. The lymphocyte released activity of the supernatants produced thrombocyte aggregation and an acceleration of clot retraction. The activity resisted heating at 56 degrees C for 30 min and was inactivated at 80 degrees C for 30 min. The active substance seems to have a molecular weight above 10,000 daltons. The findings suggest that thrombotic processes associated with cell-mediated (type IV) immune inflammation could be due, at least partially, to lymphokine effects on thrombocytes.