Regulatory T (Treg) cells and the role of immune system in tissue repair. In the area of Treg cells, he is interested in the roles of 1,25(OH)2D (i.e. the active vitamin D metabolite) and retinoic acid (RA, i.e. the active vitamin A metabolite) in the induction of Treg cells and in the treatment of immune-mediated diseases through tissue-specific delivery of these two molecules.