Systemic immunological reactivity in the absence of delayed type hypersensitivity during murine leprosy

Dissociation between cell-mediated immunity and acquired resistance in systemic murine candidiasis

Mice immunized with 10(7) heat-killed (HK) Candida albicans injected subcutaneously with or without BCG, used as an immunoadjuvant, were able to develop strong significant delayed-type hypersensitivity (DTH) against C. albicans but without any increase in specific resistance, as measured by median survival time and enumeration of yeasts inside target organ such as lungs, liver, spleen and kidneys after an intravenous (i. v.) challenge of 1 X 10(6) live C. albicans. Concomitant activation of the mononuclear phagocytic system, measured in vivo by increased resistance to L. monocytogenes, was shown to be induced in immune mice challenged i. v. with 1 X 10(6) HK C. albicans. These results are in favour of a clear distinction between DTH and acquired resistance to systemic candidiasis, even in the presence of specific activation of macrophages.

Leprosy, an overview

Leprosy is both a public health problem and a model for host-parasite relationship. There is much progress in many areas, and in most, hurdles are not only scientific but also social and financial. The following are goals to reach: 1) progress of growth of M. leprae in animals (to be able to breed armadillos in captivity or to substitute them with other animals); 2) to develop methods for in vitro culture of M. leprae; 3) to obtain antigens from M. leprae and characterize them immunologically; 4) to achieve techniques for objective diagnosis of infection with M. leprae and of leprosy (these techniques will most likely be serologic); 5) to develop methods to direct and manipulate immune response. This should include a better definition of immunologically active cells, their characterization by reliable methods, and an understanding of their functions. Immune control mechanisms and ways to channel them should also be understood; and 6) to have better methods of treatment including flexible adaptable schedules. It will be clear that "solving" the problem of leprosy requires "solving" the social problems in developing countries, as well as unraveling the mystery of the precise control of immune response. As I pointed out, the problems that we face are basically similar to those of autoimmune disorders and of cancer immunology. Research in autoimmune diseases or cancer might provide answers to questions posed by leprosy. It may also be that research in leprosy could supply answers to questions concerning cancer and autoimmunity.

The immunology of mycobacterial infections

Mycobacteria are endowed with substances that profoundly affect the immune system. Leprosy and tuberculosis exemplify broad spectra of useful and detrimental immune responses of mycobacterial infections that range from intense potentiation to severe specific adn nonspecific suppression of humoral and cellular immune elements. The cellular hypersensitivity induced by mycobacteria serves as a classical model for the analysis of specific and nonspecific immune mechanisms. Mycobacterial disease are prevalent worldwide and rank among the most important bacterial diseases. The kaleidoscope of immunologic events induced by injected mycobacteria and during infections will be reviewed from the standpoint of pathogenesis, pathology, in vitro and in vivo effects on cellular and humoral arms of the immune response, diagnosis, classification, potentiation and suppression.

Enhancement of delayed-type hypersensitivity to Trypanosoma cruzi in mice treated with Mycobacterium bovis BCG and cyclophosphamide

C57BL/10J mice treated with Mycobacterium bovis BCG and cyclophosphamide were immunized with disrupted epimastigotes or with living blood trypomastigotes from Trypanosoma cruzi and assayed for delayed hypersensitivity by footpad testing with epimastigote antigens. Enhanced and lasting reactions were observed in mice pretreated with BCG or cyclophosphamide or both and immunized with epimastigotes. Whereas BCG pretreatment clearly reduced the mortality rates of mice immunized with living blood forms, no enhancement of the delayed hypersensitivity responses was observed in animals treated with BCG or cyclophosphamide or both before infection. The production of high levels of delayed hypersensitivity in the absence of infection and its adoptive transfer with cells could help to evaluate the participation of cell-mediated immunity in the protection against T. cruzi.