The effect of drugs used in anticoagulation therapy on T lymphocyte activation in vitro. I. Heparin inhibits activation by soluble antigen or allogeneic cells but not by phytohaemagglutinin.

Heparin in concentrations corresponding to the therapeutic serum level (0.5 IU/ml) was found to inhibit proliferative responses in MLC and antigen (mumps)-stimulated cultures. Heparin had to be present early during culture to exert this effect. Heparin did not inhibit antigen-induced expression of IL-2 receptors. No inhibition was seen when heparin was present only during antigen pulsing of antigen-presenting cells. Heparin had no effect on PHA-stimulated proliferation, IL-2 production or expression of IL-2 receptors. Heparin also inhibited the IL-2 dependent growth of long-time cultured T cell lines. The inhibitory effects of heparin were not caused by a toxic effect on the cells.