The Effect of Phytohaemagglutinin on Human Foetal Cells Grown in Culture

Cell suspensions of foetal thymus, liver, spleen and bone marrow have been grown in cell culture and the effect of adding PHA observed. ³H thymidine uptake by the cells after exposure for a measured time was quantitated by autoradiographic counts performed on the initial suspensions and following culture. The initial unstimulated liver and thymic cell suspensions had a high level of ³H thymidine uptake, while that of the spleen and bone marrow cells was low. After 3 days culture the unstimulated cells from the liver, thymus and bone marrow showed very little ³H thymidine uptake, while that of the spleen was slightly increased. Foetal thymic and splenic cells responded to PHA while liver and bone marrow cells did not. The findings suggest that foetal cells of similar morphology may have different origins in the reticulo-endothelial system.