Lymphocyte culture in solid medium: I. Phytohaemagglutinin stimulation of human blood lymphocytes in chicken plasma clot cultures

Normal human blood lymphocytes were cultured in chicken plasma clots with a series of PHA-P dilutions. In this situation direct cell-to-cell contact was prevented, and thus a morphological estimate of the actual number of PHA responsive cells was possible in the absence of any cell-to-cell co-operation which might be mediated via cell contact. The distorting effects of transformed cell proliferation on quantification, and of death of the original small lymphocyte population, were similarly obviated. Between 9 and 20 per cent of those lymphocytes separated by methylcellulose and iron were PHA responsive at the optimal dose of PHA-P.