The cryopreservation of immunocompetent cells

Lymphoid cells sensitized against tumor cells in vivo were removed from sheep and mice, frozen and thawed, and then assayed for retention of cytotoxic function. Sheep lymphocytes efferent from immunized nodes have been shown previously to be cytotoxic owing to the production of antibody and these cells retained approximately 50% of their activity after freezing. The specific cytotoxicity of sensitized mouse spleen cells has been shown to be due to thymus-derived lymphocytes and such cells totally retained specific cytotoxic action after freezing. However, spleen cells also generally exhibited a degree of nonspecific cytotoxic action which disappeared on freezing and was attributed to the selective elimination of glass-adherent cells by the freezing process.