Autologous lymphocyte-mediated cytotoxicity against monocytes in canine ehrlichiosis.

: The 51Cr-release technique for detecting cytotoxicity had been adapted to immunologic studies of canine ehrlichiosis. Lymphocytes from dogs infected with Ehrlichia canis, cause of canine ehrlichiosis, were shown to be cytotoxic for autologous monocytes. The effect was dependent on the concentraton of lymphocytes, being optimal at 100:1 lymphocyte:monocyte ratio. Neither immune serum and complement, nor anti-canine globulin had any observable effect on cytotoxicity. The monocytotoxicity bore a temporal relationship to the thrombocytopenia. It is suggested that T lymphocyte activation accompanying ehrlichiosis contributes to pathogenesis of the disease and that the specific immune elimination of parasitized monocytes is antibody independent.