<ORIGINAL REPORT>INHIBITORY ACTION OF PHA ON THE APPEARANCE OF THYMIC RETICULAR CELLS IN VITRO

Abstract

When cultured rat thymus cells were treated with PHA at the time of plating, reticular cell-like cells which are regular elements of cultured thymus did not appear. However, PHA added to primary cultures on the 3rd or 5th day showed no inhibitory effect on such reticular cell-like cells. In addition it was not cytotoxic to the established reticular cell-like cells which were isolated and maintained in vitro for six months. Thymic lymphocytes activated by PHA were not aggressive against such cells. This phenomenon may be due to the selective toxicity of PHA to large round cells which are precursors of the reticular cell-like cells.