THE ROLE OF MACROPHAGES IN INCREASED MITOGEN RESPONSE OF RAT SPLENIC LYMPHOCYTES FOLLOWING IN-VITRO INCUBATION WITH VITAMIN-E

The role of macrophages (Mo) in the enhancement of lymphocyte prolifer ation by alpha-tocopherol (VE) was investigated using rat splenocytes. The proliferation of whole splenocytes was significantly higher than that of Mo-depleted splenocytes at all concentrations of concanavalin A (Con A; 0.5-10 mu g/ml). When whole and Mo-depleted splenocytes were preincubated with VE (2 mu g/ml) for 24 h, the proliferation of whole splenocytes was significantly enhanced compared to that of whole sple nocytes preincubated with medium alone. In contrast, Mo-depleted splen ocytes did not show any increase of proliferation following in vitro p retreatment with VE. When the splenic Mo pretreated with both VE (2 mu g/ml) and Con A (10 mu g/ml) for 24 h were further incubated with spl enic lymphocytes, their proliferation was significantly enhanced compa red to that of splenic lymphocytes cultured with splenic Mo pretreated with Con A. In this experiment, the medium containing 2-mercapto-etha nol (2-ME) had the ability to enhance splenic lymphocyte proliferation , which masked the enhanced effect of VE on splenic lymphocyte prolife ration. Furthermore, in vitro treatment of VE could not decrease the p roduction of prostaglandin E(2), but could enhance the production of i nterleukin 1 from splenic Mo. These results suggest that Mo play an im portant role in the proliferation of splenic lymphocytes following in vitro incubation with VE, which is closely associated with the action of VE as an immunomodulator rather than antioxidant.