Increased number of circulating suppressor T-lymphocytes in sun-induced multiple skin cancers.

The distribution of peripheral lymphocyte subsets was studied in fifteen patients with multiple nonmelanoma skin cancers, selected according to history of ultraviolet (UV) or X-ray exposure. The skin cancer was associated with previous heavy exposure to UV light in seven patients, and past exposure to x-rays in eight patients. In the UV group, the helper T-lymphocytes/suppressor T-lymphocytes (Th/Ts) ratio was abnormally low (P less than 0.01) compared with the ratios of the x-ray and control groups. The low Th/Ts ratio was associated with an absolute increase in the number of Ts. This suggests that heavy sun exposure may cause a permanent increase in the number of Ts in certain persons. These extra T-lymphocytes may in turn prevent immune rejection of transformed keratinocytes.