Immune response to a syngeneic rat tumour: development of regional node lymphocyte anergy.

The development of cellular immunity to a syngeneic squamous cell carcinoma in Wistar rats was studied by in vitro microcytotoxicity assay. Reactivity of lymphocytes from lymph nodes, spleen and blood was tested throughout the period of tumour growth. Maximum lymphocyte cytotoxicity against the tumour was observed at 2 weeks in regional lymph nodes, 4 weeks in intermediate nodes, spleen and blood, and 6 weeks in distant nodes; the intensity of these cytotoxic responses subsequently declined. In the regional nodes, lymphocytes became totally unresponsive despite the maintenance of significant cytotoxicity in intermediate nodes, spleen and blood. Local anergy may account for tumour spread to the regional node in an otherwise immunocompetent host. This anergy may be due to high local concentration of tumour antigen or antigen-antibody complexes, but it was not associated with selective changes in T and B cell proportions.