[Effect of human plasma on the in vitro formation of T-lymphocyte colonies]

T-lymphocyte colonies can be obtained from normal human peripheral blood and bone marrow, using a double layer technique which requires the simultaneous presence of peripheral blood irradiated leucocytes in the underlayer and phytohaemagglutinin in the overlayer (Foa & Catovsky, Clin. Exp. Immunol., 36, 488, 1979). The absence of either of these two factors unables colony formation. In an attempt to improve the plating efficiency 15% autologous plasma was added to the leucocyte rich underlayer, or tested alone. The results demonstrated that both leucocytes and plasma alone show a similar colony promoting activity, giving rise respectively to 160 +/- 80.4 SD and 180 +/- 113.5 SD T-colonies. The combination of both factors produced a significant increase in growth, with an overall mean of 410 +/- 190.5 colonies. Increasing concentration of plasma (1%, 5%, 10%, 15%) gave rise to a dose-dependent increase in colony growth. Furthermore, the simultaneous presence of leucocytes and plasma in the underlayer enabled good colony formation with as little as 0.1 x 105 tes cells in the overlayer. These findings indicate that both human peripheral blood leucocytes and plasma possess T-colony stimulating activity, and that optimal growth is achieved with the combination of these two factors in the underlayer.