Immunity to Tuberculosis.
Those engaged in studying this problem have not yet reached agreement on the exact nature of the mechanisms involved in humoral and cellular resistance to TB. At one time it was believed that the high susceptibility of adult negroes to TB. was due to the fact that they had not been exposed to infection in childhood and therefore had no healed primary complex. K. shows that this facile explanation is incorrect; the susceptibility of the negro is due to his inability to develop an acquired resistance, following primary infection, which would alter the character of reinfection lesions. In the same way, LURIE (1928) has shown that in the first week after inoculation in the rabbit, human type tubercle bacilli multiply even more rapidly than the bovine type organisms. The rabbit, however, soon develops a resistance to the human type tubercle bacilli, but not to the bovine which continue to multiply in the lungs and kidney. Speaking generally, K. considers that the following degrees of resistance to TB. may be recognized. The lowest degree of natural resistance will not, on first contact with the bacillus, prevent an extensive primary complex with rapid generalization and death. A higher degree of natural resistance will lead to a primary complex with perhaps some dissemination, and recovery, but no acquired resistance will follow; so that, as is often the case with negroes and South African natives, a fresh infection under bad environmental conditions will again result in a primary complex, this time with generalization and death. A still higher degree of natural resistance will cause a primary complex, recovery from which will give acquired resistance; and therefore any subsequent reinfection will not produce a primary complex but a parenchymatous lesion which tends to liquefy, cavitate, and spread by the bronchi. The work of RICH (1936) and of PAGEL (1937) showing that hypersensitivity and immunity are not necessarily associated and can be demonstrated as distinct phenomena, is quoted. Authorities are not agreed about the relative importance of cellular and humoral immunity in TB.-JOHN FRANCIS.