Differences in the cytologic characteristics of antibody-dependent cellular cytotoxicity of normal and leukemic bovine blood lymphocytes.

Peripheral blood lymphocytes from cows with chronic lymphocytic leukemia (CLL) and normal control animals were examined in vitro for antibody-dependent (AD) cellular cytotoxicity. Lymphocytes from bovine CLL showed high levels of killer (K) cell activity against antibody-coated, 3H-thymidine-labeled xenogeneic L target cells, as measured by residual radioactivity. Morphologic studies of AD lymphoid cytotoxic reaction recognized in vitro by effector-target binding revealed striking differences between leukemic and healthy cattle. The total number of target-bound AD lymphocytes was increased in all CLL animals. The data obtained show that the subpopulation of Fc receptor-bearing blood lymphocytes in CLL is significantly greater than that of healthy animals. The phenomenon of multiple, multilymphocytic, effector-target cellular complexes formed during AD leukemic lymphoid cytotoxic reaction is suggested as an additional in vitro parameter in the diagnosis of CLL.