Preliminary demonstration of human tuberculoimmunity in vitro

In this paper a method for studying human tuberculoimmunity in vitro is described. Results from its use support an explanation for human tuberculoimmunity that is like that for mouse tuberculoimmunity: that immune lymphocytes are stimulated by being cultured with immunizing antigen to make a lymphokine which enables syngeneic macrophages to kill intracellular tubercle bacilli. This method uses antigen-responding lymphocytes and effector monocytes taken in the same original 20-ml sample of venous blood. These cells are cultured separately, the lymphocytes for 72 h with antigen to make immune lymphokine and the monocytes for 7 days to become macrophages. The macrophages are then infected with attenuated or virulent tubercle bacilli and cultured for 7 days more in medium with or without the immune lymphokine. Without it they are unable to control intracellular replication of the bacilli, whereas with it they do. This lymphokine was produced only by lymphocytes of immune subjects, of whom there were three kinds: tuberculin positive naturally immunized, Mycobacterium bovis BCG immunized, and trypsin-extracted bacillary antigen immunized. This method for detecting human tuberculoimmunity in vitro should be useful for comparing experimental vaccines and for studying cellular and molecular mechanisms of human tuberculoimmunity under better controlled conditions than hitherto have been possible.