Antibody and Complement-like Factors in the Cytotoxic Action of Immune Lymphocytes

Abstract

L5178Y lymphoma cells from DBA/2 mice grow well in vitro and the cytotoxicity of immune lymphoid cells can be assayed easily in terms of the degree to which they inhibit the growth of the lymphoma. Using this system we have already shown that sheep lymph cells, collected from the efferent ducts of individual lymph nodes that had been immunized with the lymphoma, displayed a powerful and immunologically specific cytotoxic action¹. The cytotoxicity of the lymphoid cell population correlated with the percentage of large basophilic immunoblasts that were present and consequently an unequivocal cytotoxic action was only demonstrable between 4–7 days after immunization when large numbers of immunoblasts were present in the lymph. At later times the lymph was populated mainly with small lymphocytes and these cells, even when collected from hyperimmune sheep, were without demonstrable cytotoxic action in vitro. For these reasons it was concluded that the immunoblast was the cytotoxic cell. In these experiments the lymphoma cells were cultured in a medium containing 10 per cent heat-inactivated foetal calf serum.