STUDIES ON THE MECHANISM OF IMMUNITY IN TUBERCULOSIS THE ROLE OF EXTP.ACELLULAR FACTORS AND LOCAL Im~UNITY IN THE FIXATION AND INHIBITION OF GROWTH OF TUBERCLE BACILLI

The investigations of Rich (1) and his associates have cast profound doubt on the r61e of allergy in immunity to tuberculosis. Their studies intimate that both the fixation of tubercle bacilli at the site of reinfection and the inhibition of their growth may take place in the absence of exaggerated inflammation. Many studies (2) since then have indicated that there is no strict parallel between allergy and immunity. If the fate of the bacilli of reinfection is determined it has been found (3) that their destruction and the inhibition of their growth on intravenous inoculation is most marked in the presence of considerable residual primary lesions and is associated with scant inflammatory response at the site of their focalization. With slight remaining primary tuberculosis the bacilli of reinfection are less effectively inhibited~ yet the acute inflammation at the site of localization of the microorganism is much more intense. On introducing melted agar impregnated with tubercle bacilli and trypan blue subcutaneously into normal and highly immunized rabbits (4), it was found that with large doses, the early rush of lymph from the focus of reinfection is so intense that both the bacilli and the trypan blue are swept over to the draining lymph nodes much more rapidly in the sensitized than in the normal animal. However, one cannot conclude from this that in man also the exaggerated inflammation aids rather than hinders the dissemination of the bacilli of reinfection. Rabbits become only moderately sensitized to the tubercle bacillus 555