Comparison of reactions to human and avian tuberculins in leprosy patients.

A large proportion of tuber culin tests in tropical countries yield weak or doubtful reactions. Since leprosy is common in many of the countries where this phenomenon has been observed, it has been suggested that some of these anomalous r eactions may be due to nonspecific sensitization to mycobacterial antigens common to both the leprosy and the tubercle bacilli, The positive tuberculin hemagglutination reaction usually encounter ed with sera from leprosy patients, alld the positive lepromin reaction r esulting from vaccination with BGG, support the belief in such common antigens. Not all patients with leprosy, however, react to tuberculin, and the positive tuberculin reactions among them are generally ascribed to an associated infection by the tubercle bacillus. Leprosy affords no protection against tuberculosis ; instead, tuberculosis is a frequently fatal complication among patients in leprosaria. The wid ely held belief that tuberculosis infection, or vaccination with BCG, affords protection again st leprosy is similarly quite questionable. Nonspecific sensitization to tuberculin resulting from infection with leprosy may not, accordingly, be inferred merely from the high incidence of positive tuberculin reactions in leprosy populations. Differential tuberculin tests with a variety of antigens may be more informative. Such differential r eactions to mycobacteria have been well established in connection with J ohne 's disease in cattle, which produces much stronger r eactivity to avian tuberculin, as well as to johnin itself, than to mammalian tuberculin (3). The so-called "Battey" bacillus, which is held responsible for the high frequency of weak reactions to human tuberculin in the southeastern United States, also produces greater sensitivity to avian than to human tuberculin e). On the other hand, bovine and human tubercle bacilli, as well as the photochromogenic acid-fast bacilli, produce sensitization to mammalian tuberculin much greater than to the avian preparation. Greater sensitivity to avian than to human tuberculin has also been r eported in India (5) and in Africa (4), were leprosy is frequent.