Trimethylmethoxyphenyl-retinoic acid (Ro 10-1670) and lymphocyte DNA synthesis activity in vitro.

Trimethylmethoxyphenyl-retinoic acid (TMMPRA), the main active therapeutic form of etretinate, was used for in vitro studies on human lymphocytes. Lymphocyte DNA synthesis remained unchanged when TMMPRA was added to the cultures at a concentration range of 1.25-25 micrograms/ml culture medium. No modulatory activity of the drug on DNA synthesis was seen on cultured lymphocytes stimulated by lectins (phytohemagglutinin, pokeweed mitogen, concanavalin A) or by a mitogen selective for a T lymphocyte subpopulation, phorbol myristate acetate. Concanavalin A induced T suppressor cell activity tested toward the proliferative response to allogeneic stimuli was lowered by TMMPRA. The results indicated that TMMPRA alone or in the presence of lectins or phorbol myristate acetate did not inhibit or stimulate DNA synthesis activity in vitro but that the drug could lower T suppressor cell activity.