Regulatory mechanisms in graft-versus-host responses.

Graft-versus-host disease (GVHD) is induced by donor T cells cotransplanted with the stem cell graft. The main risk factors for the development of GVHD are the degree of HLA disparity between donor and recipient and the precursor frequency and intensity of T cell responses against major or minor histocompatibility antigens. However, allogeneic T cell responses do not occur in a static and sterile environment, but are modulated by the inflammatory milieu in lymphoid and GVHD target tissues that influences the functional characteristics of antigen presenting cells APCs. Here, we summarize our recent findings concerning the pro- and anti-inflammatory function of (APCs) in the gastrointestinal tract, the role of APCs in the induction of GVH and graft-versus-leukemia (GVL) responses, and their influence on suppressive effects mediated by regulatory T cells.