[AIDS and tuberculosis: the immunopathogenic processes]

HIV infection is characterized by CD4+ lymphocyte depletion manifested through the loss of the immune response capacity. The resulting immunodeficit is expressed by the blocking of immune surveillance mechanisms and, thus, by the establishment of favourable conditions to the development of opportunistic infections and/or malignant processes. In tuberculosis, the immunodeficiency associated with HIV infection makes possible the evolution of a latent infection to a clinically manifest disease. Latent tuberculosis is characterized by the intracellular persistence of some metabolically inactive Tb bacillus forms which are incapable of multiplication. The conversion of these inactive into metabolically active forms capable of multiplication is usually neutralized by immunosurveillance mechanisms. The blocking of such mechanisms in case of CD4+ cell depletion will allow the multiplication of metabolically active Tb bacillus forms, and the development of a clinically manifest tuberculosis. CD4+ lymphocyte depletion is the result of facilitating antibodies and certain cytokines, and of some autoimmune processes which also affect the non-infected CD4+ cells. Therefore, it is necessary that Tb chemoprophylaxis in HIV infected subjects should also be addressed to the processes initiating the immune deficit, which include autoimmune mechanisms as well as those facilitating HIV infection.