Trihalomethanes and colorectal cancer.

VARIOUS ANTI-TUMOUR host-defence mechanisms have been postulated to operate in man, and in particular the possible beneficial role of lymphocytic killer cells has been invoked (Cerottini & Brunner, 1974; Henney, 1977; Herberman & Holden, 1979). A possible explanation for the improved survival and reduced potential to metastasize, seen with extensive lymphocytic infiltrates of primary tumours (for review see Underwood, 1974), is the in situ tumour cell damage mediated by the infiltrating killer lymphocytes. The presence of a prominent lymphocytic infiltrate within mammary carcinomas has been found by many investigators to be a favourable prognostic sign (Moore & Foote, 1948; Berg, 1959; Anastassiades & Pryce, 1966; Hamlin, 1 968; Cutler et al., 1969; Di Paola et al., 1974; Fisher et al., 1975). The precise anti-tumour role of the tumour-infiltrating lymphocytes, however, is as yet improperly understood. We have previously described antibodydependent cellular-cytotoxicity (ADCC) mediated by killer (K) cells, and natural cytotoxicity mediated by natural killer (NK) cells, in the peripheral blood and regional tumour-draining lymph nodes of patients with mammary carcinoma, clinically localized to the breast and axilla (Eremin et al., 1977a; 1978a). In this communication we report our findings on the K and NK activity of lymphocytes isolated from the primary mammary carcinomas removed at operation from such patients.