Resynthesis of trypsinized sheep red blood cell receptors on human lymphocytes: comparison of the effects of immunopotentiators of biological and synthetic origin in vitro.

Five immunostimulants--thymosin, dialyzable leukocyte extracts containing transfer factor (DLE), isoprinosine, BM 12 531 (azimexon), and levamisole--were compared separately and in various combinations for their ability to increase the binding of sheep erythrocytes by trypsinized human peripheral blood lymphocytes in vitro. Levamisole produced the greatest enhancement when used alone, DLE produced a smaller increase, and isoprinosine, thymosin, and BM 12 531 were less effective. When combining two of these agents, the greatest increase was seen when one of the components was thymosin and the other either DLE, isoprinosine, or BM 12 531. These results indicate possible synergistic mechanisms and the possible advantage of combined therapeutic use of selected combinations of immunostimulants. In the majority of the combinations, however, inhibition rather than stimulation of rosette formation was observed.