Takayasu's arteritis: An update on physiopathology.

Takayasu's arteritis (TA) is a chronic large vessel vasculitis. The physiopathology of TA has not been completely elucidated, but it appears to be multifactorial and to mainly involve cellular immunity. The pathologic sequence could implicate stimulation from an antigen that triggers heat shock protein (HSP)-65 expression in aortic tissue which, in turn, induces MHC class I-related chain A (MICA). T-cells and natural killer (NK) cells expressing NKG2D receptors could recognize MICA, resulting in acute inflammation. Pro-inflammatory cytokines released from these infiltrating cells induce matrix metalloproteinases and amplify the inflammatory response, inducing more MHC antigen and costimulatory molecule expression on vascular cells and, thus, recruiting more mononuclear cells. Alpha-beta T-cells then infiltrate and specifically recognize one or a few autoantigens presented by a shared epitope associated with specific MHC on the dendritic cells (DC). These DC simultaneously cooperate to some extent with B-cells and determine a humoral immunity mainly constituted by anti-endothelial cell autoantibodies that could trigger complement-dependent cytotoxicity against endothelial cells. The use of corticosteroids and of other immunosuppressive agents can bring TA into remission in most patients. A better understanding of the immunological mechanisms responsible for the vascular injury has led to trials of anti-TNF-alpha agents with encouraging results. In the near future, new drugs specifically designed to target some of the mechanisms described above may be able to expand the physician's therapeutic arsenal in TA.