Allograft vascular dysfunction predisposes to arteriosclerosis and graft loss. We examined how dysfunction develops in transplanted human arteries in response to circulating allogeneic T cells in vivo using immunodeficient murine hosts. Within 7–9 days, transplanted arteries developed endothelial cell (EC) dysfunction but remained sensitive to exogenous NO. By 2 weeks, the grafts developed impaired contractility and desensitization to NO, both signs of VSMC dysfunction. These T cell–dependent changes correlated with loss of eNOS and expression of iNOS — the latter predominantly within infiltrating T cells. Neutralizing IFN-γ completely prevented both vascular dysfunction and changes in NOS expression; neutralizing TNF reduced IFN-γ production and partially prevented dysfunction. Inhibiting iNOS partially preserved responses to NO at 2 weeks and reduced graft intimal expansion after 4 weeks in vivo. In vitro, memory CD4+ T cells acted on allogeneic cultured ECs to reduce eNOS activity and expression of protein and mRNA. These effects required T cell activation by class II MHC antigens and costimulators (principally lymphocyte function-associated antigen–3, or LFA-3) on the ECs and were mediated by production of soluble mediators including IFN-γ and TNF. We conclude that IFN-γ is a central mediator of vascular dysfunction and, through dysregulation of NOS expression, links early dysfunction with late arteriosclerosis.
Kian Peng Koh, Yinong Wang, Tai Yi, Stephen L. Shiao, Marc I. Lorber, William C. Sessa, George Tellides, Jordan S. Pober