Differences in the in vitro response of lymphocytes from leukotic and normal cattle to concanavalin A

The response of cultured peripheral blood lymphocytes from cattle affected with bovine leukosis and from animals free of detectable leukosis to the nonspecific mitogen Concanavalin A ws determined by the measurement of 3H-thymidine incorporation. The stimulatory effect of the mitogen was significantly decreased in leukotic lymphocytes in comparison with normal lymphocytes. This depression was dependent on the severity of the disease. Leukotic lymphocytes showed high basal levels of spontaneous thymidine uptake possibly due to their low maturity. It is suggested that leukotic lymphocytes are not stimulated by Concanavalin A because of their B cell characteristics. A residual cell population of normal reacting lymphocytes--enriched by nylon wool column fractionation--is probably responsible for the remaining but weak in vitro reaction of leukotic lymphocytes.