Dipyridamol inhibits activation of human T lymphocytes in vitro

The effect of dipyridamol on T-lymphocyte activation was investigated. The drug did not have an irreversible toxic effect on T lymphocytes. Dipyridamol inhibited both PHA- and mumps-stimulated proliferation and the proliferative response in mixed lymphocyte cultures. The drug inhibited PHA-stimulated proliferation independent of the time when it was added during the culture period. The PHA-stimulated expression of interleukin-2 (IL-2) receptors and IL-2 production (at least for low concentrations) was not inhibited. Dipyridamol inhibited IL-2-dependent growth of T cell lines. The drug caused no inhibition when present only during antigenic pulsing.