TRANSIENT INDUCIBLE EVENTS IN DIFFERENT TISSUES - IN-SITU STUDIES IN THE CONTEXT OF THE DEVELOPMENT AND EXPRESSION OF THE IMMUNE-RESPONSES TO INTRACELLULAR PATHOGENS

Intracellular pathogens whether facultative like Mycobacterium sp., e. g. Bacillus Calmette Guerin, Listeria monocytogenes or strictly intrac ellular like Leishmania sp. initiate either asymptomatic infectious pr ocesses or disease depending both on factors of the host (genetic as w ell as environmental ones) and the infectious/pathogenic agents. In th is contribution, we first summarized informations which justify to dev elop in situ analysis to decipher the sequential events that result in different modes/classes of immune responses. How the mode of the immu ne response is determined remains a main question to address. Although it has recently become clear, in vitro, that immunocompetent cells an d their cytokines are critical to set on a stable mode oi immune respo nse, acting on naive T cells, this area deserves more in vivo studies. Indeed, peripheral T cells, at different stages of differentiation, m ay exist in vivo Ja) naive/virgin, (b) experienced, (c) effector T cel ls, depending on the level of stimulation of the immune system by eith er endogenous or exogenous (e. g. gut flora) signals. The three chosen examples illustrate our contributions in this field focusing on three different non-lymphoid tissues which may become infected: bone marrow (Bacille de Calmette Guerin), liver (Listeria monocytogenes), skin (L eishmania major). These three illustrations also allow to attract atte ntion on the interest of using mice of genetically different strains t he immune response of which is set up under different