Background-Atherosclerosis is an inflammatory disease in which interferon (IFN)-␥, the signature cytokine of Th1 cells, plays a central role. We investigated whether interleukin (IL)-17, the signature cytokine of Th17 cells, is also associated with human coronary atherosclerosis. Methods and Results-Circulating IL-17 and IFN-␥ were detected in a subset of patients with coronary atherosclerosis and in referent outpatients of similar age without cardiac disease but not in young healthy individuals. IL-17 plasma levels correlated closely with those of the IL-12/IFN-␥/CXCL10 cytokine axis but not with known Th17 inducers such as IL-1␤, IL-6, and IL-23. Both IL-17 and IFN-␥ were produced at higher levels by T cells within cultured atherosclerotic coronary arteries after polyclonal activation than within nondiseased vessels. Combinations of proinflammatory cytokines induced IFN-␥ but not IL-17 secretion. Blockade of IFN-␥ signaling increased IL-17 synthesis, whereas neutralization of IL-17 responses decreased IFN-␥ synthesis; production of both cytokines was inhibited by transforming growth factor-␤1. Approximately 10-fold fewer coronary artery-infiltrating T helper cells were IL-17 producers than IFN-␥ producers, and unexpectedly, IL-17/IFN-␥ double producers were readily detectable within the artery wall. Although IL-17 did not modulate the growth or survival of cultured vascular smooth muscle cells, IL-17 interacted cooperatively with IFN-␥ to enhance IL-6, CXCL8, and CXCL10 secretion. Conclusions-Our findings demonstrate that IL-17 is produced concomitantly with IFN-␥ by coronary arteryinfiltrating T cells and that these cytokines act synergistically to induce proinflammatory responses in vascular smooth muscle cells.

Inflammation is associated with the pathogenesis of coronary atherosclerosis, although the mechanisms remain unclear. We investigated whether cytokine secretion by innate immune responses could contribute to the production of proarteriosclerotic Th1-type cytokines in human coronary atherosclerosis. Cytokines were measured by ELISA in the plasma of patients with coronary atherosclerosis undergoing cardiac catheterization. IL-18 was detected in all subjects, whereas a subset of patients demonstrated a coordinated induction of other IFN-γ-related cytokines. Specifically, elevated plasma levels of IL-12 correlated with that of IFN-γ and IFN-γ-inducible chemokines, defining an IFN-γ axis that was activated independently of IL-6 or C-reactive protein. Systemic inflammation triggered by cardiopulmonary bypass increased plasma levels of the IFN-γ axis, but not that of IL-18. Activation of the IFN-γ axis was not associated with acute coronary syndromes, but portended increased morbidity and mortality after 1-year follow-up. IL-12 and IL-18, but not other monokines, elicited secretion of IFN-γ and IFN-γ-inducible chemokines in human atherosclerotic coronary arteries maintained in organ culture. T cells were the principal source of IFN-γ in response to IL-12/IL-18 within the arterial wall. This inflammatory response did not require, but was synergistic with and primed for TCR signals. IL-12/IL-18-stimulated T cells displayed a cytokine-producing, nonproliferating, and noncytolytic phenotype, consistent with previous descriptions of lymphocytes in stable plaques. In contrast to cognate stimuli, IL-12/IL-18-dependent IFN-γ secretion was prevented by a p38 MAPK inhibitor and not by cyclosporine. In conclusion, circulating IL-12 may provide a mechanistic link between inflammation and Th1-type cytokine production in coronary atherosclerosis.

1 These authors contributed equally to this work.

Background-Heparin, used clinically as an anticoagulant, also has antiinflammatory properties and has been described to inhibit interferon (IFN)-␥ responses in endothelial cells. We investigated the effects of heparin on the IFN-␥-inducible chemokines IP-10/CXCL10, I-TAC/CXCL11, and Mig/CXCL9, which play important roles in the vascular recruitment of IFN-␥-producing Th1 cells through interactions with their cognate receptor, CXCR3. Methods and Results-Patients undergoing coronary artery bypass grafting were studied because coronary atherosclerosis is recognized as a Th1-type inflammatory disease and the subjects required systemic heparinization. Plasma levels of IP-10, I-TAC, and Mig increased immediately after heparin administration and diminished promptly after heparin antagonism with protamine. These effects were independent of detectable circulating IFN-␥ or the IFN-␥ inducer interleukin-12. We confirmed previous reports that heparin inhibits the IFN-␥-dependent production of CXCR3 chemokine ligands using atherosclerotic coronary arteries in organ culture. In addition to prolonged treatment decreasing chemokine secretion, heparin rapidly displaced membrane-associated IP-10 from cultured endothelial cells that did not express CXCR3 and reduced the IP-10 -dependent transendothelial migration of T helper cells under conditions of venular shear stress. Finally, heparin administration to immunodeficient mouse hosts decreased both the recruitment and accumulation of memory T cells within allogeneic human coronary arteries. Conclusions-Besides

SRL plus CsA prevented allograft arteriopathy, correlating with suppression of intragraft interferon-gamma, suggesting that SRL effects may result from anti-inflammatory consequences from inhibiting interferon-gamma.