Properties of lymphocytes which confer adoptive immunity to tuberculosis in rats.

Following immunization of rats with BCG there was added to thoracic duct lymph a population of sensitized lymphocytes which conferred adoptive immunity to tuberculosis upon syngeneic recipients. At an early stage of immunization, 5 days after BCG inoculation, the sensitized cells were large and medium lymphocytes as evidenced by their sensitivity to vinblastine. On day 8, the sensitized cell population was partially resistant to vinblastine and by day 28 it was totally resistant. The vinblastine resistant cells have the functional properties of small lymphocytes, since they recirculate freely from the blood to lymph, and can confer long lasting immunity upon recipient rats. The data imply that protective immunity against the tubercle bacillus is transferred by a family of newly-formed lymphocytes, the most immature of which are immunoblasts or large lymphocytes. As the response matures, sensitized small lymphocytes are delivered to the circulation and comprise an increasing proportion of the protective cell population.