The functions of GSH are not only inhibitory as described above for the inflammatory response. In fact, GSH is essential for some functions of the immune system, both innate and adaptive, including T-lymphocyte proliferation, 38, 39 phagocytic activity of polymorphonuclear neutrophils (PMN), 40 and dendritic cell functions, 41 and is also important for the first step of adaptive immunity, consisting of the antigen presentation by antigen-presenting cells (APC). Indeed, cell-mediated immunity requires that protein antigens be first degraded in the endocytic vesicles of APCs (eg, macrophages, dendritic cells), so that the smaller peptides can be presented on the cell surface by the major histocompatibility complex to activate proliferation of antigen-specific T cells. One of the first steps in antigen degradation and processing is the reduction of disulfide bonds, 42 which requires GSH. 43 It should also be noted that although GSH inhibits the production of most inflammatory cytokines, it is required to maintain an adequate interferongamma (IFN-gamma) production by dendritic cells, 44 which is essential for the host defense against intracellular pathogens such as mycobacteria. 45 This essential role of GSH in immunity might explain why in many diseases, not only AIDS, decreased GSH levels are associated with an increased susceptibility to infection. These include COPD, 46 cystic f ibrosis, 47, 48 influenza infection, 49 and alcoholism, 50,51 as ethanol impairs Th1/Th2 balance via GSH depletion 52 (Table 3) .