STUDIES ON THE MECHANISM OF IMMUNITY IN TUBERCULOSIS : THE MOBILIZATION OF MONONUCLEAR PHAGOCYTES IN NORMAL AND IMMUNIZED ANIMALS AND THEIR RELATIVE CAPACITIES FOR DIVISION AND PHAGOCYTOSIS.

1. Tuberculous and vaccinated rabbits and guinea pigs mobilize mononuclear phagocytes at the site of a non-specific inflammation with greater rapidity than do normal animals, just as they respond to tubercle bacilli. 2. The succession of cells that characterizes inflammation in general is accelerated in allergic rabbits and guinea pigs in response to non specific irritants. 3. The pH at the site of reinfection with tubercie bacffli in immun ized rabbits and guinea pigs and at the site of a non-specific inflammation in the latter is slightly lower than in a similar site in a normal animal. 4. No constant relation was found between the mobifization of mononuclears and the hydrogen ion concentration at the site of inflammation. 5. The rate of mitotic and amitotic division of mononuclears in allergic rabbits and guinea pigs in response to non-specific irritants is greater than in normal animals. 6. Mononuclears derived from actively tuberculous or vaccinated guinea pigs exhibit greater in vitro phagocytic capacity for carbon particles than mononuclears obtained from normal animals. 7. Mononuclears of tuberculous rabbits ingest more staphylococci than the phagocytes of the same type originating from normal animals. 8. Mononuclears originating from actively tuberculous rabbits and guinea pigs exhibit greater in vitro phagocytic capacity for tuberde bacilli than mononuclears obtained from normal animals. 9. The enhancement of the phagocytic capacity for tubercie bacilli afforded mononuclears by vaccination with a bacillus of low virulence is lower, and of questionable significance. 10. The increased phagocytic activity of mononuclears derived from tuberculous or vaccinated rabbits and guinea pigs for tubercie bacilli and for non-specific particulate matter occurs in media containing sera derived from normal and from tuberculous individuals. 11. The more rapid mobilization of mononuclears by immunized animals in response to specific as well as non-specific irritants is associated with their increased physiological activity. The significance of this enhanced activity conferred by the tuberculous process on the mesenchyme cells is discussed in relation to the mechanism of immunity to tuberculosis and other phenomena.