Lymphocyte in vitro Cytotoxicity: Specific Release of Lymphotoxin-like Materials from Tuberculin-sensitive Lymphoid Cells

Abstract

ALLOGRAFT immunity and delayed hypersensitivity reactions are caused chiefly by the action of host immune lymphoid cells¹. Although these reactions have been much studied in vivo and in vitro, the mechanism of cell destruction is essentially unknown. There have been reports from this laboratory that a cell-free toxic factor released by immune and phytohaemagglutinin (PHA)-stimulated non-immune mouse lymphocytes is essential in the in vitro destruction of target L cells². This factor, termed lymphotoxin (LT), caused in vitro cytolysis of both continuous and primary cells obtained from many animal species³. Later work showed that lymphocytes from various animal species, including man, could be stimulated ^{in vitro} to release LT, in the absence of target cells, by treatments which induce lymphocyte transformation, that is the mixed lymphocyte reaction, PHA and xenogeneic antibody⁴. It was therefore of interest to investigate whether lymphoid cells obtained from animals with delayed hypersensitivity to soluble antigens could be induced in vitro to release LT-like materials. We wish to report here that in the case of tuberculin hypersensitivity in mice, guinea-pigs and man, non-specific toxic materials are released when the cells are cultured in the presence of specific antigen.