Depletion of CD8+ or CD4+ lymphocytes enhances susceptibility to transplantable ultraviolet radiation-induced skin tumours.

BACKGROUND Immunosuppressed patients are extremely susceptible to cutaneous squamous cell carcinoma, suggesting that immunosurveillance by T lymphocytes protects against this ultraviolet radiation-induced tumour. MATERIALS AND METHODS To determine the relative contribution of CD8+ and CD4+ lymphocytes to immunosurveillance, we tested the effects of CD8+ or CD4+ T lymphocyte depletion on the susceptibility of C3H/HeN mice to a syngeneic UVR-induced skin tumour cell line. RESULTS Both anti-CD8 and anti-CD4 treatment significantly enhanced the growth of transplanted tumours. In CD8-depleted animals, tumours grew rapidly in all animals. Tumour growth in CD4-depleted animals was slower, and 50% of these mice eventually rejected their tumours. In CD4-depleted mice that did not reject their tumours, an early period of tumour growth was followed by partial regression of the tumour; a second phase of rapid tumour growth then supervened. CONCLUSION Our findings suggest that both CD8+ and CD4+ lymphocytes contribute to immunosurveillance against skin cancer.