High frequency of central memory regulatory T cells allows detection of liver recipients at risk of early acute rejection within the first month after transplantation

Abstract

Several studies have analyzed the potential of T regulatory cells (Treg cells) as biomarkers of acute rejection (AR). The aim of the present multicenter study was to correlate the percentage of peripheral Treg cells in liver graft recipients drawn at baseline up to 12 months after transplantation with the presence of AR. The percentage of central memory (cm) Treg cells (CD4(+)CD25(high)CD45RO(+)CD62L(+)) was monitored at pre-transplant and at 1 and 2 weeks, and 1, 2, 3 and 6 months and 1 year post-transplantation. The same validation standard operating procedures were used in all participating centers. Fifteen patients developed AR (23.4%). Hepatitis C virus recurrence was observed in 16 recipients, who displayed low peripheral blood cmTreg levels compared with patients who did not. A steady increase of cmTregs was observed during the first month after transplantation with statistically significant differences between AR and non-AR patients. The high frequency of memory Treg cells allowed us to monitor rejection episodes during the first month post-transplantation. On the basis of these data, we developed a prediction model for assessing risk of AR that can provide clinicians with useful information for managing patients individually and customizing immunosuppressive therapies.

Keywords: Treg; acute rejection; liver transplantation; receiver operating characteristic curves.

Fig. 1.

Peripheral blood memory T regulatory cell gating strategy in orthotopic liver transplant recipients. Peripheral blood lymphocytes were stained with monoclonal antibodies to CD4, CD25, CD62L and CD45RO gated on CD4⁺ T viable cells.

Fig. 2.

Longitudinal changes in cmTregs within the first year after OLT. (A) cmTreg cell frequency expressed as a % of total number of CD4⁺ T lymphocytes; (B) absolute number of cmTreg expressed as a number of CD4⁺ T-lymphocytes/mm³. The lines reflect the median and interquartile range at any time point. Only significant P values are shown. *P < 0.05; **P < 0.01 and ***P < 0.001.

Fig. 3.

Percentage of medium fluorescence intensity (MFI) as frequency of peripheral blood cmTreg cells with respect to the total number of peripheral blood CD4⁺ T cells in liver transplant recipients. (A) % of cmTreg cells in AR and NAR patients at 1 month after transplant. (B) % of cmTreg in HCV and NHCV patients at 1 month post-transplant. (C) % of cmTreg cells in in HCV and NHCV patients at 6 months post-transplant. (D) % of cmTreg cells in HCV and NHCV patients at 12 months post-transplant. Data show mean ± SD.

Fig. 4.

(A) Changes in the frequency of cmTreg cells within the first month after transplantation. The differences in the peripheral levels of cmTreg cells between patients with AR (upper line) and without AR (lower line) were significant (P = 0.019) when comparing the levels together corresponding to the first week + second week + first month. (B) During acute allograft rejection episodes, cmTreg cell levels were higher than observed before rejection or after successful anti-rejection treatment (P = 0.022).

Fig. 5.

Post-transplantation ROC curves for discriminating between rejectors and non-rejectors in liver transplant recipients. In liver patients, cutoff values for % cmTreg (represented as a percentage of total number of CD4⁺ peripheral blood T-cells) within 1 month after transplantation, AUC = 0.724 (95% CI: 0.567–0.849); P = 0.0106. CI, confidence interval.