MYCOBACTERIAL INFECTIONS - ARE THE OBSERVED ENIGMAS AND PARADOXES EXPLAINED BY IMMUNOSUPPRESSION AND IMMUNODEFICIENCY

The enigmas and paradoxes observed in tuberculous patients, in Bacille Calmette-Guerin-vaccinated people and in Bacille Calmette-Guerin-trea ted cancer patients have been examined, in an attempt to explain them through the mechanisms of immunodeficiency and immunosuppression. A du al effect is postulated: an immunosuppression induced by the infecting mycobacteria that adds to a pre-existing or emerging state of immunod eficiency of the infected individual. The immunological cellular and h umoral anergies observed at the beginning of a tuberculous therapy are usually lifted after the first two weeks of treatment. This restorati on of immune responsiveness may be attributed to the destruction or to the growth inhibition of Immunosuppressive mycobacteria. The observat ion that drugs cytocidal in vitro do not always sterilize the patients under treatment whereas bacteriostatic drugs do, may find an explanat ion in the dual immunosuppression induced by cytocidal drugs and mycob acteria. The fact that Bacille Calmette-Guerin applied as an immunothe rapy to residual cancer has either a favorable or an unfavorable actio n may be due to the immunosuppressive activity attached to some Bacill e Calmette-Guerin strains and to some cancers. The variable protective activity of Bacille Calmette-Guerin vaccines may be due to the immuno logical status of the vaccinated people and the compositional differen ces between strains. The protective activity of subunit vaccines in ex perimental models can be attributed to the elimination of immunosuppre ssive factors present in whole killed mycobacteria.