Induction and suppression of the cytotoxic activity of human lymphocytes in vitro by heterologous anti-lymphocyte serum.

  • 1 October 1969
    • journal article
    • Vol. 5  (4) , 381-98
Abstract
Heterologous anti-lymphocyte sera were demonstrated to induce a cytotoxic potential in normal non-immunized human lymphocytes against allogeneic fibroblast target cells. The cytotoxicity-inducing capacity was restricted to certain dilutions of anti-lymphocytic serum above and below which no cytotoxic effect was obtained. This optimal concentration shifted towards higher dilutions in sera taken late during the immunization course. The antisera were shown to stimulate the DNA-synthesis in lymphocytes and to aggregate the lymphocytes to the target cells. The DNA-synthesis and the aggregation as well were maximal at the same dilution of anti-lymphocytic serum which induced cytotoxicity. No cytotoxic effect was demonstrable on sheep fibroblasts. It is, therefore, suggested that the anti-lymphocytic serum antibody induces lymphocyte-mediated cytotoxicity against allogeneic fibroblasts in a two step manner: it stimulates the lymphocytes into a cytotoxic state; it aggregates the human lymphocytes to the human fibroblasts by virtue of its bivalent structure.