Surface markers on human b and t lymphocytes. VI. Cytotoxicity against cell lines as a functional marker for lymphocyte subpopulations.

The spontaneous lymphocyte mediated cytotoxicity (SLMC) of cells from normal donors against 19 different established cell lines was analysed. All normal lymphocytes were cytotoxic in all combinations tested in a17h 51-Cr release assay. ALMC was found to be mediated by a minor subpopulation of lymphocytes with Fc/C3 receptors. Non-cytotoxic SRBC binding T-lymphocytes could be induced to become cytotoxic by the addition of Con A to the incubation medium. SLMC and lectin-induced cytotoxicity were briefly characterized. It is argued that SLMC is a non-specific non-immunological reaction which must be taken into consideration when lymphocytes from cancer patients are tested against tumour-cell lines in vitro. Futhermore, SLMC and letin-induced cytotoxicity are proposed as functional markers for Fc/C3-binding lymphocytes and SRBC binding lymphocytes respectively.