Stimulation of syngeneic and allogeneic lymphoid cells by tumour cells in vitro.

August and Wistar rat lymph node cells were found to respond well to PHA stimulation and in mixed lymphocyte culture, as determined by an increased incorporation of 3H-thymidine. August rat lymph node cells were also stimulated by incubation with irradiated syngeneic tumour cells. Allogeneic Wistar rat lymph node cells produced a larger response to the August tumour cells. The response of syngeneic and allogeneic lymph node cells was reduced by pretreating the tumour cells with a Wistar anti-tumour serum. Pretreating the tumour cells with sera from normal or tumour bearing rats also reduced the response of syngeneic lymph node cells but did not reduce the response of allogeneic lymph node cells.