Immune sources of transforming growth factor-beta1 reduce transplant arteriosclerosis: insight derived from a knockout mouse model

oxLDL antibody inhibits MCP-1 release in monocytes/macrophages by regulating Ca2+ /K+ channel flow

oxLDL peptide vaccine and its antibody adoptive transferring have shown a significantly preventive or therapeutic effect in atherosclerotic animal model. The molecular mechanism behind this is obscure. Here, we report that oxLDL induces MCP‐1 release in monocytes/macrophages through their TLR‐4 (Toll‐like receptor 4) and ERK MAPK pathway and is calcium/potassium channel‐dependent. Using blocking antibodies against CD36, TLR‐4, SR‐AI and LOX‐1, only TLR‐4 antibody was found to have an inhibitory effect and ERK MAPK‐specific inhibitor (PD98059) was found to have a dramatic inhibitory effect compared to inhibitors of other MAPK group members (p38 and JNK MAPKs) on oxLDL‐induced MCP‐1 release. The release of cytokines and chemokines needs influx of extracellular calcium and imbalance of efflux of potassium. Nifedipine, a voltage‐dependent calcium channel (VDCC) inhibitor, and glyburide, an ATP‐regulated potassium channel (K⁺_ATP) inhibitor, inhibit oxLDL‐induced MCP‐1 release. Potassium efflux and influx counterbalance maintains the negative potential of macrophages to open calcium channels, and our results suggest that oxLDL actually induces the closing of potassium influx channel – inward rectifier channel (K_ir) and ensuing the opening of calcium channel. ERK MAPK inhibitor PD98059 inhibits oxLDL‐induced Ca²⁺/K_ir channel alterations. The interfering of oxLDL‐induced MCP‐1 release by its monoclonal antibody is through its FcγRIIB (CD32). Using blocking antibodies against FcγRI (CD64), FcγRIIB (CD32) and FcγRIII (CD16), only CD32 blocking antibody was found to reverse the inhibitory effect of oxLDL antibody on oxLDL‐induced MCP‐1 release. Interestingly, oxLDL antibody specifically inhibits oxLDL‐induced ERK MAPK activation and ensuing Ca²⁺/K_ir channel alterations, and MCP‐1 release. Thus, we found a molecular mechanism of oxLDL antibody on inhibition of oxLDL‐induced ERK MAPK pathway and consequent MCP‐1 release.

Transforming growth factor beta expression by human vascular cells inhibits interferon gamma production and arterial media injury by alloreactive memory T cells

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.

Kruppel-like factor KLF10 targets transforming growth factor-beta1 to regulate CD4(+)CD25(-) T cells and T regulatory cells

CD4(+)CD25(+) regulatory T cells (T regs) play a major role in the maintenance of self-tolerance and immune suppression, although the mechanisms controlling T reg development and suppressor function remain incompletely understood. Herein, we provide evidence that Kruppel-like factor 10 (KLF10/TIEG1) constitutes an important regulator of T regulatory cell suppressor function and CD4(+)CD25(-) T cell activation through distinct mechanisms involving transforming growth factor (TGF)-beta1 and Foxp3. KLF10 overexpressing CD4(+)CD25(-) T cells induced both TGF-beta1 and Foxp3 expression, an effect associated with reduced T-Bet (Th1 marker) and Gata3 (Th2 marker) mRNA expression. Consistently, KLF10(-/-) CD4(+)CD25(-) T cells have enhanced differentiation along both Th1 and Th2 pathways and elaborate higher levels of Th1 and Th2 cytokines. Furthermore, KLF10(-/-) CD4(+)CD25(-) T cell effectors cannot be appropriately suppressed by wild-type T regs. Surprisingly, KLF10(-/-) T reg cells have reduced suppressor function, independent of Foxp3 expression, with decreased expression and elaboration of TGF-beta1, an effect completely rescued by exogenous treatment with TGF-beta1. Mechanistic studies demonstrate that in response to TGF-beta1, KLF10 can transactivate both TGF-beta1 and Foxp3 promoters, implicating KLF10 in a positive feedback loop that may promote cell-intrinsic control of T cell activation. Finally, KLF10(-/-) CD4(+)CD25(-) T cells promoted atherosclerosis by approximately 2-fold in ApoE(-/-)/scid/scid mice with increased leukocyte accumulation and peripheral pro-inflammatory cytokines. Thus, KLF10 is a critical regulator in the transcriptional network controlling TGF-beta1 in both CD4(+)CD25(-) T cells and T regs and plays an important role in regulating atherosclerotic lesion formation in mice.

Kidney transplantation: mechanisms of rejection and acceptance

We describe the molecular and cellular mechanisms believed to be responsible for the rejection of renal allografts, including acute T cell-mediated rejection, acute antibody-mediated (humoral) rejection, rejection mediated by the innate immune system, and chronic rejection. We present mechanisms of graft acceptance, including accommodation, regulation, and tolerance. Studies in animals have replicated many pathologic features of acute and chronic rejection. We illuminate the pathogenesis of human pathology by reflection from experimental models.

Atorvastatin attenuates transplant-associated coronary arteriosclerosis in a murine model of cardiac transplantation

Accelerated coronary arteriosclerosis remains a major problem for the long-term survival of cardiac transplant recipients. However, the pathogenesis of transplant vasculopathy is poorly understood and there is no effective therapy. HMG-CoA reductase inhibitors, or statins, are widely prescribed to lower plasma cholesterol level. Accumulating evidence indicates that statins have various effects on vascular cells which are independent of their lipid-lowering effect. We investigated whether orally administered atorvastatin, one of the most potent statins, inhibits the development of intima hyperplasia in a mouse model of cardiac transplantation. Cardiac allografts from DBA mice were transplanted heterotopically into B10.D2 mice. Mice were administered either vehicle or atorvastatin everyday by gavage. Morphometrical analysis revealed that atorvastatin significantly reduced the development of coronary arteriosclerosis on the cardiac allografts harvested at one month. Immunohistochemical analysis revealed that atorvastatin attenuated infiltration of inflammatory cells with reduced expression of TGF-beta and adhesion molecules. These results suggest that atorvastatin may be effective in preventing transplant-associated arteriosclerosis along with other immunosuppressive agents.

The Angiotensin II Type 1 Receptor Blocker Candesartan Attenuates Graft Vasculopathy

OBJECTIVE

Transplant arteriosclerosis remains the major cause of graft failure after cardiac transplantation, although recent progress in immunosuppressive therapy has dramatically improved short-term survival of recipient. We investigated the effects of the angiotensin II type 1 receptor (AT(1)R) blocker candesartan on the development of transplant arteriosclerosis in a murine model of cardiac transplantation.

MATERIALS AND METHODS

Hearts from DBA/2 (H-2(d)) mice were heterotopically transplanted into B10.D2 (H-2(d)) mice. Recipients were treated with oral administration of candesartan (1 mg/kg per day) or vehicle. Allografts were analyzed at 14 or 30 days after transplantation.

RESULTS

Candesartan significantly reduced the development of coronary arteriosclerosis (intima/media ratio: 0.86 +/- 0.09 versus 0.57 +/- 0.10, P < 0.05), without affecting the degree of parenchymal rejection at 30 days. There was no significant difference in the expression of adhesion molecules and cytokines at 14 days. Candesartan significantly reduced the number of peripheral mononuclear cells that differentiated into smooth muscle-like cells in the presence of basic fibroblast growth factor and platelet-derived growth factor BB (27.1 +/- 3.1 versus 17.3 +/- 1.8 cells/HPF, P < 0.05).

CONCLUSIONS

Angiotensin II may play a role in the pathogenesis of transplant arteriosclerosis. Blockade of AT(1)R might be effective as a prophylactic therapy for transplant arteriosclerosis along with conventional immunosuppressive drugs.

Prevention of chronic allograft nephropathy with vitamin D

Chronic allograft nephropathy (CAN) is the leading cause of late allograft loss in kidney transplantation. Interstitial fibrosis and glomerulosclerosis are characteristic of CAN. Transforming growth factor beta-1 (TGFbeta-1) is associated with both of these histologic findings in the transplant setting. Recent studies have suggested that vitamin D signaling pathways may interact with and regulate TGFbeta-1 mediated events. We examined the efficacy of 1,25-dihydroxyvitamin D(3), the active metabolite of vitamin D [1,25-(OH)(2)D(3)], the active metabolite of vitamin D, as monotherapy to prolong allograft survival and preserve renal function in a rat model of CAN, the Fisher 344 to Lewis model. Recipients went without treatment or were treated with cyclosporine A (CSA; 10 days) or 1,25(OH)(2)D(3) (1000, 500 or 250 ng/kg/day). Grafts were harvested at the time of rejection or at 24 weeks post-transplant. A portion of the graft was processed for histology and immunohistochemistry and a second portion was analyzed for protein expression by western blotting. Not only did 1,25-(OH)(2)D(3) treatment significantly prolong graft survival, but it also prevented histological changes associated with CAN. 1,25-(OH)(2)D(3) treatment significantly decreased Smad 2 expression. This TGFbeta signaling molecule is likely involved in fibrosis. Moreover, 1,25-(OH)(2)D(3) treatment increased Smad 7 expression, an important feedback molecule in the TGFbeta-1 signaling pathway. This suggests that 1,25-(OH)(2)D(3) interacts with TGFbeta-1 in limiting histological injury in this model of CAN. Furthermore, 1,25-(OH)(2)D(3), treatment increased expression of matrix metalloproteinase 2 (MMP-2), thus directly affecting levels of another important matrix molecule. Taken together our data suggests that 1,25-(OH)(2)D(3) mitigates CAN in this model by altering TGFbeta-1 and matrix-regulating molecules.

Peripheral Expansion of Circulating T-Helper 1 Cells Predicts Coronary Endothelial Dysfunction After Cardiac Transplantation

OBJECTIVE

We sought to assess the importance of Th1 cells for the development of cardiac allograft vasculopathy.

BACKGROUND

Despite improvements in immunosuppressive regimens, chronic rejection still represents one of the leading causes of death beyond the first year after heart transplantation. Chronic rejection is characterized by the development of transplant vasculopathy. The exact mechanisms initiating and promoting this form of arteriosclerosis in the human setting remain unclear.

METHODS

In order to assess the role of T lymphocytes we characterized differentiated T-cell subsets in 32 transplant recipients early after transplantation using RT-PCR, flow cytometry and immunhistochemistry and matched these findings with endothelial function testing as an early clinical indicator of transplant vasculopathy.

RESULTS

Allograft endothelial dysfunction (ED) was defined as a compromised coronary flow reserve to acetylcholine (CFVR<2 in 8 of 32 transplant recipients). In these patients, mRNA transcript levels for the T-helper (Th)1 signature cytokines interferon (INF)-gamma (p<0.0001) and interleukin (IL)-2 (p<0.005) and STAT4 (Th1 transcription factor, p<0,05) were significantly higher than in the remaining 24 patients with normal endothelial function. This correlated with a significant increase in circulating CD3(+)/IFN-gamma(+)-T-cells (28.6 +/- 4.4% vs 8.7 +/- 5.6%; p<0.0001). In contrast, transcript levels for the Th2 signature cytokines (IL-4, IL-10) and STAT6 (Th2 transcription factor) did not differ significantly between the two groups.

CONCLUSIONS

Peripheral expansion of circulating Th1 but not Th2 cells predicts coronary ED after cardiac transplantation. Therefore, quantification of circulating T cells might be a diagnostic tool to predict development of ED in patients after heart transplantation.

Temporal and spatial characterization of cellular constituents during neointimal hyperplasia after vascular injury: Potential contribution of bone-marrow-derived progenitors to arterial remodeling

BACKGROUND

Exuberant smooth muscle cells (SMCs) hyperplasia is the major cause of postangioplasty restenosis. We suggested that circulating smooth muscle progenitor cells might contribute to lesion formation after vascular injury.

METHODS

We extensively investigated the cellular constituents during neointimal formation after mechanical vascular injury.

RESULTS

A large wire was inserted into the mouse femoral artery, causing complete endothelial denudation and marked enlargement of the lumen with massive apoptosis of medial SMCs. At 2 h, the injured artery remained dilated with a thin media containing very few cells. A scanning electron microscopy showed fibrin and platelet deposition at the luminal side. One week after the injury, CD45-positive hematopoietic cells accumulated at the luminal side. Those CD45-positive cells gradually disappeared, whereas neointimal hyperplasia was formed with alpha-smooth muscle actin (SMA) positive cells. Bone marrow cells and peripheral mononuclear cells differentiated into alpha-SMA-positive cells in the presence of PDGF and basic FGF. Moreover, in bone marrow chimeric mice, bone-marrow-derived cells substantially contributed to neointimal hyperplasia after wire injury.

CONCLUSION

These results suggest that early accumulation of hematopoietic cells may play a role in the pathogenesis of SMC hyperplasia under certain circumstances.

Reduced expression of transforming growth factor beta 1 exacerbates pathology in an experimental asthma model

Allergic asthma is characterized by airway hyperreactivity (AHR), eosinophilic airway inflammation and elevated serum IgE levels. T-helper 2 (Th2) cells play a critical role in the pathogenesis of asthma, but the immunological mechanisms that inhibit Th2 cell function in vivo are not well understood. Conflicting results regarding the protective role of Th1 cytokines and TGF-beta in asthma have been reported. To further investigate the role of TGF-beta(1 )in asthma, we examined mice heterozygous for deletion of the TGF-beta(1) gene (TGF-beta(1) (+/-) mice) in a murine asthma model. While TGF-beta(1) (+/-) mice seem phenotypically normal, they express only about 30% of wild type TGF-beta(1) protein levels as shown before. The reduced expression of TGF-beta(1) is accompanied by a strikingly increased eosinophilic inflammation and mucus secretion in response to ovalbumin (OVA) sensitization. Moreover, TGF-beta(1) (+/-) mice develop significantly enhanced Th2-cytokine levels, decreased IFN-gamma production and increased levels of OVA-specific IgE in serum. In contrast, AHR in response to methacholine is not altered significantly. Our data demonstrate that reduced expression of TGF-beta(1) exacerbates pathology in an experimental asthma model and support the view that the elevated levels of TGF-beta(1) in asthmatic airways might be, at least in part, a result of anti-inflammatory compensation by this cytokine.

A novel polymorphism of the gene encoding furin, a TGF-β1 activator, and the influence on cardiac allograft vasculopathy formation

BACKGROUND

Coronary vasculopathy (CV) is an important determinant of survival following cardiac transplantation. We have previously shown that G915C polymorphism of the Transforming Growth Factor-beta1 (TGF-beta1) gene strongly influences CV development. Furin is a proprotein convertase enzyme important in TGF-beta1 activation. We investigated for polymorphism within the promoter region of the gene for furin (fur). Allelic variation of the fur gene, in conjunction with TGF-beta1 polymorphism, was subsequently related to the development of CV.

METHODS AND RESULTS

The fur gene promoter region (position -1199 to +39) was analysed by SSCP and sequencing. A C/T single nucleotide substitution polymorphism at position -231* was identified. Using PCR the fur and TGFB1 genotypes were identified in 115 cardiac transplant recipients. CV was diagnosed at routine surveillance post-transplant coronary angiography. Fur polymorphism had no influence on vasculopathy development; median time to diagnosis, *C/C homozygotes, 2.27 years (2.10-4.32), *C/T heterozygotes 2.97 years (2.09-4.24), *T/T homozygotes 2.65 years (2.33-4.08), (P=0.95). Allelic variation did not influence Kaplan Meier actuarial analysis of disease onset (P=0.54). Ninety-three percent of recipients were high TGF-beta1 producers. We used fur polymorphism to substratify patients with the +915*G/G TGFB1 (high producing) allele. Fur polymorphism did not influence CV development within this TGF-beta1 high producer cohort, when analysed by time to first diagnosis and Kaplan Meier testing.

CONCLUSIONS

We have described a novel polymorphism at position -231* in the gene encoding furin. The fur -231* single nucleotide polymorphism in isolation, or in conjunction with TGFB1 polymorphism, is not useful as a genetic risk marker for cardiac transplant associated coronary vasculopathy.

The angiotensin II type 1 receptor blocker valsartan attenuates graft vasculopathy

OBJECTIVE

Transplant arteriosclerosis remains the major cause of graft failure after cardiac transplantation. Here, we investigated the effects of the angiotensin II type 1 receptor blocker valsartan on the development of transplant arteriosclerosis in a murine model of cardiac transplantation.

METHODS

Hearts from DBA/2 (H-2(d)) mice were heterotopically transplanted into B10.D2 (H-2(d)) mice. Recipients were treated with oral administration of valsartan (10 mg/kg/day) or vehicle.

RESULTS

Morphometrical analysis of the cardiac allografts harvested at 30 days revealed that valsartan significantly reduced the development of coronary atherosclerosis (intima/media ratio: 0.39 +/- 0.05 vs. 0.66 +/- 0.08, P < 0.01). At two weeks after transplantation, there was no significant difference between the two groups in expression of adhesion molecules and cytokines. Valsartan significantly reduced the number of peripheral mononuclear cells that differentiated into smooth muscle-like cells in the presence of basic fibroblast growth factor and platelet-derived growth factor BB (18.0 +/- 1.5 vs. 30.3 +/- 4.4 cells/HPF, P = 0.01).

CONCLUSIONS

These results suggest that angiotensin II plays a role in the pathogenesis of transplant arteriosclerosis and that blockade of angiotensin II type 1 receptor might be effective as a prophylactic therapy for transplant arteriosclerosis along with conventional immunosuppressive drugs.

Transforming growth factor beta in cardiovascular development and function

Transforming growth factor betas (TGFbetas) are pleiotropic cytokines involved in many biological processes. Genetic engineering and tissue explanation studies have revealed specific non-overlapping roles for TGFbeta ligands and their signaling molecules in development and in normal function of the cardiovascular system in the adult. In the embryo, TGFbetas appear to be involved in epithelial-mesenchymal transformations (EMT) during endocardial cushion formation, and in epicardial epithelial-mesenchymal transformations essential for coronary vasculature, ventricular myocardial development and compaction. In the adult, TGFbetas are involved in cardiac hypertrophy, vascular remodeling and regulation of the renal renin-angiotensin system. The evidence for TGFbeta activities during cardiovascular development and physiologic function will be given and areas which need further investigation will be discussed.

Paracrine secretion of transforming growth factor-beta1 in aneurysm healing and stabilization with endovascular smooth muscle cell therapy

BACKGROUND

Identification of molecular factors involved in artery wall stabilization after extracellular matrix injury elicited by inflammation and proteolysis has a major role in the development of new therapies for atherosclerosis. A study from our group demonstrated that endovascular seeding of vascular smooth muscle cells (VSMCs) promotes healing and stabilizes experimental aneurysms by downregulating matrix metalloproteinase and upregulating tissue inhibitor of metalloproteinase and collagen gene expression. We analyzed expression of transforming growth factor-beta (TGF-beta) and its receptors in experimental aneurysms treated with endovascular VSMC therapy.

METHODS AND RESULTS

Aneurysms were generated in Fischer 344 rats by 14-day orthotopic implantation of a segment of guinea pig abdominal aorta (xenograft). During an endovascular repeat operation, syngeneic VSMCs were seeded in the aneurysm, always resulting in aneurysm diameter stabilization after 8 weeks, whereas diameter of control aneurysms infused with culture medium further increased. Seven days after repeat operation the intima or thrombus was separated from the aneurysmal wall in the two groups. Reverse transcriptase polymerase chain reaction with the domestic gene 18s as a standard demonstrated that aneurysm stabilization was associated with a statistically significant increase in TGF-beta(1), but not TGF-beta(2) or TGF-beta(3), messenger RNA levels in the intima. Enzyme-linked immunosorbent assay demonstrated increased TGF-beta(1) protein in the aneurysmal wall. mRNA levels of the two serine and threonine kinase TGF-beta receptors remained unchanged.

CONCLUSIONS

Healing and stabilization of aneurysms with endovascular cell therapy is associated with a specific pattern of gene expression, resulting in paracrine secretion of TGF-beta(1). Our study provides insight into the molecular mechanisms of arterial aneurysm healing and stabilization.

Upregulation of PAI-1 is mediated through TGF-beta/Smad pathway in transplant arteriopathy

BACKGROUND

Plasminogen activator inhibitor type 1 (PAI-1) is the primary physiologic inhibitor of plasminogen activator in vivo. Increased PAI-1 expression is associated with arteriosclerosis. Transforming growth factor-beta (TGF-beta) induces PAI-1 production via Smads.

METHODS

In vivo, TGF-beta receptors (TbetaRs), Smad2, Smad3, and Smad4, PAI-1, and Smad2 phosphorylation were examined by immunohistochemistry in 3 native aortas, 14 rat aortic syngrafts, and 19 allografts collected at 15, 30, and 45 days post-transplantation. In vitro, phosphorylation of Smad2 and induction of PAI-1 mRNA in human aortic smooth muscle cells (SMCs) in response to TGF-beta treatment were detected by Western blot and by TaqMan real-time RT-PCR, respectively.

RESULTS

Immunohistochemical staining revealed that vascular parenchymal cells contained TbetaRI, TbetaRII, Smad2, Smad3, and Smad4, known signaling transducers for TGF-beta/Smad pathway, in all samples. Intense staining for phospho-Smad2 was observed in 94% of endothelial cells (ECs), 86% of intimal cells, 27% of medial SMCs, and 38% of adventitial cells at all 3 time points in all aortic allografts, but only in 5% of ECs in syngrafts. PAI-1 immunoreactivity was detected in similar number of cells, and from consecutive sections, phospho-Smad2 colocalized with PAI-1, in the aortic allografts. Low basal level PAI-1 expression was observed in aortic syngrafts and native vessels. Smad2 phosphorylation and time-dependent PAI-1 induction were detected in cultured SMCs upon TGF-beta treatment.

CONCLUSIONS

Phospho-Smad2 staining in aortic allografts indicates the activation of TGF-beta signaling in allo-transplantation; and co-localization of PAI-1 and phospho-Smad2 suggests that PAI-1 upregulation is mediated mainly by TGF-beta/Smad pathway in aortic allografts.

Initial T-cell activation required for transplant vasculopathy in retransplanted rat cardiac allografts

BACKGROUND

A precise understanding of immunological mechanisms is needed to prevent transplant vasculopathy.

METHODS

The developing process of transplant vasculopathy was investigated by retransplanting rat cardiac allografts and measuring the expressions of 21 different genes inside the retransplanted allografts under nonimmunosuppressive conditions.

RESULTS

Significant transplant vasculopathy developed if WKY hearts were grafted to LEW and retransplanted to WKY 5 days after the initial grafting, but it did not in allografts retransplanted 3 days after the initial grafting. The disease did not progress in retransplanted isografts or if nude rats were used as the initial recipients. However, the development of transplant vasculopathy was not affected by changing the second recipients to the F1 progeny of donor x recipient or to nude animals. Among the expressions of 21 different genes observed in allografts at 1, 14, 30, or 60 days after retransplantation, those of T-cell activation-related genes, such as interferon-y and Fas ligand, showed the earliest and the most dramatic difference between 3- and 5-day-retransplanted allografts whereas macrophage/monocyte activation-related genes showed little difference. Furthermore, reverse transcription-polymerase chain reaction analyses of allografts retransplanted to nude animal indicated that T cells of the initial recipient origin survive and remain activated even 60 days after retransplantation.

CONCLUSIONS

The T-cell response occurring between 3 and 5 days after grafting was identified as the critical parameter to the disease progression. Once alloreactive T cells enter a graft, they may be able to survive a long period and promote chronic rejection.

Possible role of proinflammatory cytokines in heart allograft coronary artery disease

Transplant coronary artery disease (Tx-CAD) is the main determinant of long-term prognosis after heart transplantation. Immunologic processes may play a central role in the development of Tx-CAD, but the pathogenesis has not been fully clarified. We examined plasma levels of the proinflammatory cytokines tumor necrosis factor-alpha (TNF-alpha), interleukins (IL)-1beta and IL-6, and the CC-chemokine macrophage chemoattractant protein-1 (MCP-1) in 62 cardiac allograft recipients undergoing yearly heart catherization with coronary angiography for evaluation of graft disease. In this cross-sectional study, we found significantly increased levels of IL-1beta, IL-6, TNF-alpha, and MCP-1 compared with healthy controls even several years (median 7 years) after transplantation in periods with no intercurrent illness. Although no significant differences were found in plasma levels of IL-1beta and TNF-alpha between patients with (n = 25) and without (n = 37) Tx-CAD, the Tx-CAD group had significantly increased levels of IL-6 and MCP-1 compared with both controls and transplant recipients without Tx-CAD. Increased IL-6 levels compared with controls were found only in patients with Tx-CAD. Finally, while there was no significant relation between Tx-CAD and altered lipid status, the combination of high plasma concentrations of IL-6 or MCP-1 and high low-density lipoprotein cholesterol was strongly associated with increased occurrence of Tx-CAD. These findings indicate that cardiac allograft recipients have a persistent immune activation long term after transplantation. This activation, as particularly reflected in increased MCP-1 and IL-6 levels, may be related to the development of Tx-CAD.