Characterization of rabbit antithymocyte globulins-induced CD25+ regulatory T cells from cells of patients with end-stage renal disease.

BACKGROUND.: Rabbit antithymocyte globulins (rATGs) are known to convert CD4CD25FoxP3 T cells from healthy individuals to CD4CD25FoxP3 T cells. In this study, we investigated the effect of rATG on the induction of regulatory T cells (Tregs) from blood cells of patients with end-stage renal disease who are candidates for transplantation and rATG-induction therapy. The induced Tregs were analyzed and compared with naturally occurring CD4CD25FoxP3T cells. METHODS.: The CD25 T cells of pretransplant patients (n=7) and healthy controls (n=4) were stimulated with rATG or control rabbit immunoglobulins for 24 hr. The phenotype of induced Tregs was examined by flow cytometry, and their function was studied in the conventional suppression assay. Further characterization was performed by mRNA analyses. RESULTS.: After 24 hr, the percentage of CD4CD25FoxP3CD127 T cells and CD8CD25FoxP3CD127 T cells became higher in the rATG-treated samples compared with the rabbit immunoglobulin-treated samples (P<0.01). The rATG-induced CD25T cells, whether CD4 or CD8 inhibited the allogeneic responses of CD25 effector T cells as vigorously as natural CD25T cells. However, the proportion of FoxP3 within the top 2% rATG-induced CD4CD25T-cells was lower than within the natural CD4CD25T-cells (11%+/-2% vs. 95%+/-5%, P<0.01). The mRNA-expression levels of interleukin-27, interleukin-10, interferon-gamma, perforin, and granzyme B were markedly higher compared with natural CD25T-cells (all P=0.03), whereas CTLA4 (P=0.03), transforming growth factor-beta (P=0.02), and RORgammat (P=0.04) were lower. CONCLUSION.: rATG allows the induction of Tregs from patient peripheral blood mononuclear cell in vitro. In comparison with natural Tregs, the rATG-induced Tregs are phenotypically distinct but have similar regulatory activities. rATG may beneficially contribute to the mechanisms that control alloreactivity.

Conversion from calcineurin inhibitor to mycophenolate mofetil-based immunosuppression changes the frequency and phenotype of CD4+FOXP3+ regulatory T cells.

BACKGROUND: CD4+FOXP3+ regulatory T cells (Treg) depend on interleukin (IL)-2 for their function and survival. By interfering with the IL-2 production, calcineurin inhibitors (CNI) may negatively affect Treg. Here, we describe the effects of conversion from CNI to mycophenolate mofetil (MMF) monotherapy on renal function, and on Treg frequency and phenotype in liver transplant recipients. METHODS: Patients (n=16) with renal impairment on CNI were converted to MMF and received a single dose of IL-2-receptor blocking antibody (Daclizumab). Control patients (n=8) continued CNI treatment. RESULTS: Renal function rapidly and significantly improved after conversion. Daclizumab treatment resulted in a 75% blocking of CD25 at 1 month causing a significant reduction in the percentage of CD4+CD25+ cells but not affecting the percentage of CD4+CD25+Foxp3+ cells. Six months after conversion to MMF, the percentage of CD4+CD25+Foxp3+ cells increased significantly by 125%. FOXP3 mRNA analysis of mononuclear cells confirmed the enrichment of Foxp3 in peripheral blood. Interestingly, the CD25 expression level on CD4+Foxp3+, but not CD4+Foxp3-, cells significantly increased compared with preconversion. CONCLUSION: Conversion to MMF increases the percentage and CD25 expression of CD4+FOXP3+ cells indicating that MMF therapy can overturn the repressive effect of CNI on circulating Treg levels and therefore may promote Treg-mediated suppression of alloreactivity.

Generation of donor-specific regulatory T-cell function in kidney transplant patients.

BACKGROUND: In the search for mechanisms that can induce and maintain transplant tolerance, donor-specific CD4CD25FoxP3 regulatory T cells have been frequently mentioned. However, it remains to be demonstrated, whether these cells are generated after clinical transplantation. METHODS: We prospectively analyzed the phenotype and function of peripheral regulatory CD4CD25 T cells of 79 patients before, 3, 6, and 12 months after kidney transplantation. The immune regulatory capacities of CD4CD25 T cells were assessed by their depletion from peripheral blood mononuclear cells and in co-culture with CD25 responder T-cells in the mixed lymphocyte reactions. RESULTS: In the first year after transplantation, the number and proportion of CD4CD25 T cells significantly decreased (P<0.05 and P<0.001, respectively). In the mixed lymphocyte reactions, we observed donor-specific hyporesponsiveness in the presence of significantly increased proliferation to third and fourth Party-Ag, (P<0.001 and P<0.05, respectively). Furthermore, functional analysis of CD25 cells showed that the effect of depletion of these cells from peripheral blood mononuclear cells, and their suppressive capacities in co-culture with donor-Ag stimulated CD25 responder T-cells (1:10 ratio) significantly improved (P<0.01 and P<0.001, respectively). Moreover, the difference between the stimulation with donor-Ag and third Party-Ag became apparent at 6 months after transplantation. CONCLUSIONS: These findings demonstrate that donor-specific CD4CD25 regulatory T-cell function is generated in fully immunosuppressed renal recipients in the first year after transplantation.

End-stage renal failure and regulatory activities of CD4+CD25bright+FoxP3+ T-cells.

BACKGROUND: The defensive immune system in patients with end-stage renal failure is impaired at multiple levels. This state of immune incompetence is associated with continuous activation of the immune system. An additional explanation for this state of activation may be the disturbed function of CD4(+)CD25(bright+)FoxP3(+) regulatory T-cells. METHODS: The phenotype and function of peripheral regulatory T-cells from patients with end-stage renal failure (N = 80) and healthy controls (N = 17) was studied by flow cytometry, RT-PCR and mixed lymphocyte reaction. Patients were on haemodialysis (N = 40), peritoneal dialysis (N = 26) or not treated with dialysis yet (N = 14). The latter group had a glomerular filtration rate of <20 ml/min/ 1.73 m(2). RESULTS: The basal IL-2 mRNA level was high in patient-PBMC (P = 0.0002 versus healthy controls). The absolute number of CD4(+)CD25(bright+) T-cells was low in patients (P < 0.05 versus healthy controls). Furthermore, proliferation of patient-PBMC upon allogeneic stimulation was impaired (P < 0.0001 versus healthy controls). The regulatory function of CD4(+)CD25(bright+) T-cells was determined in the setting of direct allorecognition. First, the effect of depletion of CD25(bright+) cells from patient-PBMC on proliferation was low. Second, co-culture of CD25(bright+) cells with CD25(neg/dim) cells (1:10 ratio) showed impaired regulatory function (P < 0.001 versus healthy controls), which was especially pronounced in patients on dialysis. The FOXP3 mRNA level was also low upon stimulation (P = 0.0002 versus healthy controls). CONCLUSIONS: In line with previous studies, we observed an overactivated but functionally compromised immune system in patients with end-stage renal failure. It now appears that in this setting, regulation by CD4(+)CD25(bright+)FoxP3(+) T-cells is also impaired.

The effect of rabbit anti-thymocyte globulin induction therapy on regulatory T cells in kidney transplant patients.

BACKGROUND: Prevention of alloreactivity by rabbit anti-thymocyte globulins (rATG) may not only result from immunodepletion but also from the induction of T cells that control allogeneic immune responses. In the present prospective and controlled study, we investigated the effect of rATG on the frequency, function and phenotype of peripheral immunoregulatory CD4+ T cells in kidney transplant (KTx) patients. METHODS: After transplantation, 16 patients received ATG-induction therapy and triple therapy consisting of tacrolimus, MMF and steroids. The control group (n = 18) received triple therapy only. By flow cytometry, T cells were analysed for CD25, FoxP3, CD127, CD45RO and CCR7. To study their suppressive capacities, CD25bright T cells were co-cultured with CD25(-/dim) effector T cells (Teff) in mixed lymphocyte reactions (MLR), stimulated with donor and third party (3P) antigens. RESULTS: Pre-transplant levels of FoxP3+CD127(-/low) T cells were 6% of CD4+ T cells. One week post-ATG treatment, no measurable numbers of regulatory T cells were present (P < 0.01). After 4 weeks, the cell numbers of CD4+FoxP3+CD127(-/low) T cells slowly reappeared and thereafter remained low (P < 0.01). At 14 weeks, a significant shift towards the CD45RO+CCR7+ (central memory) phenotype within CD4+FoxP3+ T cells was observed (P < 0.01). At 26 weeks, the proliferative alloresponses of the PBMC and CD25(-/dim) Teff profoundly decreased compared to pre-transplant (P = 0.01 and P = 0.02 respectively), while the regulatory capacity of the CD25bright T cells, of which 90% consisted of FoxP3+CD127(-/low) T cells, remained unaffected. The CD25bright T cells suppressed the anti-donor (94%) and 3P responses (93%). CONCLUSION: Our findings show that rATG therapy does not spare peripheral immunoregulatory T cells in vivo, but after regeneration preserves their suppressive activity.

Functional analysis of CD4+ CD25bright T cells in kidney transplant patients: improving suppression of donor-directed responses after transplantation.

BACKGROUND: The role of CD4(+) CD25(bright) regulatory T cells (Treg) in controlling alloreactivity is established, but little is known whether antigen-specific Treg are induced in fully immunosuppressed kidney transplant patients. METHODS: The frequency and function of CD25(bright) T cells of nine stable kidney transplant patients before and 0.5-2 yr after transplantation were measured. Patients received triple therapy consisting of cyclosporine, mycophenolate mofetil and prednisone. To investigate the influence of transplantation and immunosuppression on Treg function, we compared their suppressive capacities pre- and post-transplantation using mixed lymphocyte reactions and kept the CD25(-/dim) effector T-cell (Teff) population constant. RESULTS: After transplantation, the percentage of CD4(+) CD25(bright) T cells significantly decreased from 8.5% pre-transplant to 6.9% post-transplant (median, p = 0.05). However, the lower percentage of post-transplant CD4(+) CD25(bright) T cells was not associated with reduced, but rather improved suppressor function of these cells. The proliferative response of pre-transplant Teff to donor-antigens was more profoundly suppressed by post-transplant Treg than by pre-transplant Treg (pre-transplant 18% vs. post-transplant 55% median, p = 0.03) and was comparable against third party antigens at a CD25(bright):CD25(-/dim) ratio of 1:20. CONCLUSIONS: In immunosuppressed kidney transplant patients, the donor-directed suppressive capacity of CD4(+) CD25(bright) regulatory T cells improved, which may contribute to the development of donor-specific hyporesponsiveness against the graft.

Inflammation and apoptosis genes and the risk of restenosis after percutaneous coronary intervention.

OBJECTIVES: Genetic factors appear to be important in the development of restenosis after percutaneous coronary intervention, as well as in the process of inflammation, a pivotal factor in restenosis. Caspase-1, interleukin-1-receptor and protein tyrosine phosphatase nonreceptor type 22 are important mediators in the inflammatory response and caspase-1 also in apoptosis. Therefore, we examined whether polymorphisms in these candidate genes are related to the risk of developing restenosis after percutaneous coronary intervention. METHODS: The GENetic DEterminants of Restenosis-project is a multicenter prospective follow-up study. The 5352G/A (L235L) caspase-1-polymorphism, the 7464C/G (A124G) interleukin-1r-polymorphism and the 1858C/T (R620W) protein tyrosine phosphatase nonreceptor type 22-polymorphism were genotyped. To examine the functional effect of the caspase-1 polymorphism, mature plasma interleukin-1beta levels were measured by enzyme-linked immunosorbent assay in lipopolysaccharide-stimulated whole blood from a subpopulation of patients. RESULTS: A total of 3104 patients, age 62.1+/-10.7 years, were included after successful percutaneous coronary intervention. A significant association between the 5352AA genotype of the caspase-1 gene and target vessel revascularization (relative risk 2.2, 95% confidence interval 1.32-3.76) was observed after correcting for clinical variables. Angiographic analysis of a subgroup of patients (N=478) also showed an increased risk for developing restenosis for patients having the 5352GA/AA genotype (P=0.001). The results were corroborated, although they were not statistically significant, by somewhat higher mature interleukin-1beta levels in patients with the 5352AA genotype. CONCLUSIONS: The present study shows that patients with the 5352AA genotype in the caspase-1 gene are at increased risk of developing restenosis. If confirmed by other studies, screening patients for this genotype can lead to better risk stratification and provide indications for improving individual treatment; for instance, by providing a new target for drug-eluting stents.