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Optimal defense against pathogens requires adaptive immunity in which specialized antigen-specific T cell subsets play an important role. Protection against endosomal pathogens requires type 1 T helper (Th1) cells, protection against helminths Th2 cells, protection against bacteria Th17 cells and protection against viruses cytotoxic T (Tc) cells. Importantly, the function of these effector T cells is inhibited by T regulatory (Tr) cells, that  prevent in this way excessive host tissue damage, autoimmunity and allergy. In fact, each immune response is characterized by a certain balance between the immunogenic effector T cells and tolerogenic Tr cells, which is orchestrated by antigen-presenting dendritic cells. Dendritic cells not only present antigen to naïve T cells, but also express molecules that enable these naïve T cells to become a certain effector T cell or a regulatory T cell. We have proposed the concept that the expression pattern of these T cell polarizing molecules by dendritic cells is flexible and depends on how these dendritic cells have been conditioned by micro-environmental factors, such as pathogens or host tissue reactivity factors. Failure of adaptive immunity can in many cases be explained by failure of the tuning role of dendritic cells.

Current research further focus on the way dendritc cells promote the development of Th17, Tc and Tr cells by studying the interaction between pathogens or tissue factors and dendritic cells on the one hand and the subsequent interaction between dendritic cells and naïve T cells on the other hand. The results will be used in the design of vaccines or therapies of chronic inflammatory diseases (allergy, cancer) based on the ex vivo manipulation or the in vivo targeting of dendritic cells.