Effect of L-asparaginase and hydrocortisone on human lymphocyte transformation and production of a mononuclear leucocyte chemotactic factor in vitro

Human peripheral lymphocytes stimulated in vitro with PHA produce a soluble factor which is chemotactic for homologous monocytes. The synthesis of this factor was found to precede the blastogenic response as measured by [³H] thymidine incorporation. In cultures of unseparated leucocytes the maximum of chemotactic activity was detected after 24 hr, whereas in supernatants from purified lymphocyte suspensions the maximal synthesis occurs after 72 hr. High doses of L-asparaginase from E. coli which have been found to prevent lymphocyte transformation completely have no influence on the production of the chemotactic factor. Therefore it seems possible that the induction of DNA synthesis by PHA and its effect on the production of a chemotactic factor depend on different biochemical mechanisms. In contrast hydrocortisone leads to a dose-dependent inhibition of both DNA synthesis and chemotactic response.