The interaction of normal lymphocytes and cells from lymphoid cell lines. I. The nature of the activation process.

Human peripheral lymphocytes from all donors tested were mitotically activated when cultured in the presence of X-irradiated cells from continuously cultivated lymphoid cell lines (LCL). X-irradiated cells from LCL originating from normal individuals were effective as well as those of Burkitt's tumour origin and cells from LCL reported to be free of herpes-like virus were as effective as those reported to contain virus. The activation was of much greater intensity than the normal mixed lymphocyte reaction but occurred over a similar culture period. The reaction occurred only under conditions permitting direct cell contact between the two populations of cells. Most stimulation was obtained with viable X-irradiated LCL cells. Disrupted LCL cells were ineffective.