A human lymphokine released by mononuclear blood cells upon contact with CEA

As revealed by the macrophage electrophoretic mobility (MEM) technique mononuclear blood cells from certain cancer patients respond to carcinoembryonic antigen (CEA). This phenomenon appeared to be due to a specific lymphokine release. In this study, the lymphokine activity of supernatant pools was stepwise enriched by gel filtration on Sephadex. The mediator activity was recovered within a molecular mass region less than 47 kDA. The lymphokine was highly enriched during further gel filtration steps and showed a single activity peak in the molecular mass region of 23.5 kDa. Gel filtrations of appropriate control supernatants resulted in biologically inactive fractions. The lymphokine was heat-labile at 56 degrees C, showed a clear-cut, dose-dependent effect on macrophages, and could be blocked by fucose. Preparative gel electrophoresis of radiolabeled and unlabeled lymphokine resulted in two corresponding peaks of biological activity and radioactivity.