CD127(low) expression in CD4+CD25(high) T cells as immune biomarker of renal function in transplant patients

Profiling of mRNA of interstitial fibrosis and tubular atrophy with subclinical inflammation in recipients after kidney transplantation

Interstitial fibrosis and tubular atrophy (IFTA) with inflammation (IFTA-I) is strongly correlated with kidney allograft failure. Diagnosis of IFTA-I accurately and early is critical to prevent graft failure and improve graft survival. In the current study, through analyzing the renal allograft biopsy in patients with stable function after kidney transplantation (STA), IFTA and IFTA-I group with semi-supervised principal components methods, we found that CD2, IL7R, CCL5 based signature could not only distinguish STA and IFTA-I well, but predict IFTA-I with a high degree of accuracy with an area under the curve (AUC) of 0.91 (P = 0.00023). Additionally, IRF8 demonstrated significant differences among STA, IFTA and IFTA-I groups, suggesting that IRF8 had the capacity to discriminate the different classifications of graft biopsies well. Also, with Kaplan-Meier and log-rank methods, we found that IRF8 could serve as the prognostic marker for renal graft failure in those biopsies without rejection (AUC = 0.75) and the recipients expressing high had a higher risk for renal graft loss (P < 0.0001). This research may provide new targets for therapeutic prevention and intervention for post-transplantation IFTA with or with inflammation.

Differing effects of rapamycin or calcineurin inhibitor on T-regulatory cells in pediatric liver and kidney transplant recipients

In a cross-sectional study, we assessed effects of calcineurin inhibitor (CNI) or rapamycin on T-regulatory (Treg) cells from children with stable liver (n = 53) or kidney (n = 9) allografts several years posttransplant. We analyzed Treg number, phenotype, suppressive function, and methylation at the Treg-specific demethylation region (TSDR) using Tregs and peripheral blood mononuclear cells. Forty-eight patients received CNI (39 as monotherapy) and 12 patients received rapamycin (9 as monotherapy). Treg numbers diminished over time on either regimen, but reached significance only with CNI (r =-0.424, p = 0.017). CNI levels inversely correlated with Treg number (r =-0.371, p = 0.026), and positively correlated with CD127+ expression by Tregs (r = 0.437, p = 0.023). Patients with CNI levels >3.6 ng/mL had weaker Treg function than those with levels <3.6 ng/mL, whereas rapamycin therapy positively correlated with Treg numbers (r = 0.628, p = 0.029) and their expression of CTLA4 (r = 0.726, p = 0.041). Overall, CTLA4 expression, TSDR demethylation and an absence of CD127 were important for Treg suppressive function. We conclude that rapamycin has beneficial effects on Treg biology, whereas long-term and high dose CNI use may impair Treg number, function and phenotype, potentially acting as a barrier to attaining host hyporesponsiveness to an allograft.

Circulating lymphocyte subsets in different clinical situations after renal transplantation

Phenotypic characterization of T and B lymphocytes allows the discrimination of functionally different subsets. Here, we questioned whether changes in peripheral lymphocyte subset distribution reflect specific clinical and histopathological entities after renal transplantation. Sixty-five renal transplant recipients with either histologically proven (sub)clinical acute rejection or chronic allograft dysfunction, or without abnormalities were studied for their peripheral lymphocyte subset composition and compared with 15 healthy control individuals. Naive, memory and effector CD8(+) T-cell counts were measured by staining for CD27, CD28 and CD45RO/RA. In addition, we studied the CD25(+) CD4(+) T-cell population for its composition regarding regulatory Foxp3(+) CD45RO(+) CD127(-) cells and activated CD45RO(+) CD127(+) cells. Naive, non-switched and switched memory B cells were defined by staining for IgD and CD27. We found a severe decrease in circulating effector-type CD8(+) T cells in recipients with chronic allograft dysfunction at 5 years after transplantation. Percentages of circulating CD25(+) CD127(low) CD4(+) regulatory T cells after transplantation were reduced, but we could not detect any change in the percentage of CD127(+) CD45RO(+) CD4(+) activated T cells in patients at any time or condition after renal transplantation. Regardless of clinical events, all renal transplant recipients showed decreased total B-cell counts and a more differentiated circulating B-cell pool than healthy individuals. The changes in lymphocyte subset distribution probably reflect the chronic antigenic stimulation that occurs in these transplant recipients. To determine the usefulness of lymphocyte subset-typing in clinical practice, large cohort studies are necessary.

Absolute of CD4(+)CD25(+)FOXP3(+) regulatory T-cell count rather than its ratio in peripheral blood is related to long-term survival of renal allografts

CD4(+)CD25(+)Foxp3(+) regulatory T cells (Tregs) may reflect the immune status of kidney transplant (KTx) recipients. Since individual KTx recipients show different lymphocyte counts, we hypothesized that the Treg absolute count rather than its peripheral ratio was more related to long-term survival. We enrolled 42 patients with more than 5-year KTx survival: 32 patients with stable graft function and 10 suffering chronic rejection (CR group). The stable group was divided into four subgroups according to graft survival time: subgroups A (5-6 years); B (6-7 years); C (7-8 years); and D (>8 years). Healthy volunteers were enrolled as controls. We compared the peripheral ratio and absolute count of CD4(+), CD4(+)CD25(+), and CD4(+)CD25(+)Foxp3(+) Tregs. Treg peripheral ratio was not significantly different among the three groups. However, the Treg absolute count was higher among the stable than the CR group (P < .01). Meanwhile, both Treg ratios and absolute counts were altered with renal graft survival. Treg absolute count in subgroups B and C were not only higher than that in subgroup A (P < .05), but also was significantly higher than that in the CR control group or (P < .05). Interestingly, both the Treg ratio and absolute count in subgroup D were lower than those in subgroups B and C (P < .05). Treg quantitation, which alters with graft survival time, may contribute to long-term acceptance of renal allografts. Compared to Treg peripheral ratio, the absolute count may be a superior index to estimate KTx recipient immune status.

Peripheral blood sampling for the detection of allograft rejection: biomarker identification and validation

Currently, acute allograft rejection can only be detected reliably by deterioration of graft function confirmed by allograft biopsy. A huge drawback of this method of diagnosis is that substantial organ damage has already taken place at the time that rejection is diagnosed. Discovering and validating noninvasive biomarkers that predict acute rejection, and chronic allograft dysfunction, is of great importance. Many studies have investigated changes in the peripheral blood in an attempt to find biomarkers that reflect changes in the graft directly or indirectly. Herein, we will review the promises and limitations of the peripheral blood biomarkers that have been described in the literature so far.