Abstract
Arteriosclerosis is characterized by the local activation of effector T cells leading to production of proinflammatory cytokines, such as IFN (interferon)-γ and IL-17, within the vessel wall. Conversely, the production of antiinflammatory cytokines, for example, TGF-β, by regulatory lymphocytes is known to inhibit both the differentiation of naïve T cells into effector T cells and the development of arteriosclerosis in murine models. We investigated the role of TGF-β on the alloreactivity of human effector memory T cells (Tem). Quiescent vascular cells, but not Tem, expressed TGF-β. Blockade of TGF-β activity in cocultures of CD4(+) Tem with allogeneic endothelial cells significantly increased IFN-γ, but not IL-17, secretion. Additionally, serologic neutralization of TGF-β in immunodeficient mouse hosts of human coronary artery grafts into which allogeneic human T cells were adoptively transferred resulted in heavier medial infiltration by Tem, greater loss of medial smooth muscle cells and increased IFN-γ production within the grafts without significantly reducing either intimal injury or IL-17 production. Protective effects of TGF-β may be limited by fewer TGF-β-expressing vascular cells within the intimal compartment, by a reduction in the expression of TGF-β by vascular cells in rejecting grafts, or possibly to less effective suppression of Tem than naïve T cells.