Role of regulatory T cell populations in controlling graft vs host disease.

Immune function is critical in health and disease. The control and regulation of immune reactions is an area of intense investigation that has important implications for allogeneic hematopoietic cell transplantation. Immune reactions are regulated in a number of important ways. Compartmentalization of immune responses and the production of both pro-inflammatory and anti-inflammatory cytokines play a major role. More recently several populations of T cells that regulate immune responses termed regulatory T cells have been identified. This manuscript will focus on CD4+CD25+FoxP3+ natural regulatory T cells (T(reg)) and αβTCR+CD4+NK1.1+ natural killer T (NK-T) cells which both suppress graft vs host disease but appear to function by distinct mechanisms.