Tissue-specific regulatory T cells: biomarker for acute graft-vs-host disease and survival

Abstract

Regulatory T cells (Tregs) are a subset of CD4(+) T cells that are characterized by the expression of CD25 and Foxp3 and are capable of suppressing alloimmune responses. We assessed whether high frequencies of circulating skin or gut tissue-specific Tregs at engraftment could predict acute graft-vs-host disease (aGVHD) incidence and survival in a cohort of hematopoietic cell transplant (HCT) recipients. Tregs were analyzed at engraftment in 74 patients receiving HCT. Treg skin-homing (CLA(+)) or gut-homing (α(4)β(7)(+)) subsets were identified by flow cytometry, and patients were divided into high CLA(+) Tregs or high α(4)β(7)(+) Tregs groups, using the 75(th) percentile of tissue-specific Treg percentages as a threshold. At day +100 post-HCT, the cumulative incidence of any stage skin or gut aGVHD was significantly lower in those patients with high CLA(+) Tregs or high α(4)β(7)(+) Tregs at engraftment, respectively (high CLA(+) Tregs, 24.0% vs low CLA(+) Tregs, 55.1%; p = 0.011 for skin aGVHD or high α(4)β(7)(+) Tregs, 47.3% vs low α(4)β(7)(+) Tregs, 74.5%; p = 0.029 for gut aGVHD). The 2-year probabilities of overall survival and nonrelapse mortality were 73.4% and 7.5% among patients with high frequencies of tissue-specific Tregs vs 49.4% and 36.1% for those with both low CLA(+) Tregs and low α(4)β(7)(+) Tregs (p = 0.039, p = 0.010). These results suggest that a threshold value for CLA(+) or α(4)β(7)(+) Tregs could be used to predict important HCT outcomes, and to direct the rationale use of tissue-specific pre-emptive therapies to decrease clinical aGVHD and improve HCT survival.

Figure 1

Number of patients who underwent allogeneic hematopoietic cell transplantation, accrued to study, and were included in the final Treg analysis. ATG, antithymocyte globulin; PBMCs, peripheral blood mononuclear cells.

Figure 2

CLA⁺ and α₄β₇⁺ Tregs can be identified at the time of neutrophil recovery after allogeneic hematopoietic cell transplantation. (A) Patient with preferential expansion of skin-homing (CLA⁺) Tregs (CD4⁺CD45RO⁺CD25⁺Foxp3⁺CD127^lo cells). (B) Patient with preferential expansion of gut-homing (α₄β₇⁺) Tregs (CD4⁺CD45RO⁺CD25⁺Foxp3⁺CD127^lo cells). (C) Treg expression of CLA and α₄β₇ are inversely related.

Figure 3

Clinical outcomes stratified by Treg tissue-homing subsets. Probabilities of (A) overall survival, (B) disease-free survival, and (C) non-relapse mortality based on high CLA⁺ or high α₄β₇⁺ Tregs (n = 43) vs low CLA⁺ and low α₄β₇⁺ Tregs (n = 31). High CLA⁺ Tregs: CLA⁺ Tregs/Tregs ≥3.25%; High α₄β₇⁺ Tregs: α₄β₇⁺ Tregs/Tregs ≥21.8%.