CD45RA-CD25highCD127-CD4+ activated regulatory T cells are correlated with de novo donor-specific anti-HLA antibody formation after kidney transplantation in standard immunosuppression

Although de novo donor-specific anti-HLA antibodies (dnDSA) remain a barrier for human kidney transplantation (KTx), the role of regulatory T (Treg) cells in dnDSA formation remains unknown. To address this question, we evaluated Treg cell subsets in peripheral blood mononuclear cells in 15 healthy volunteers and 59 KTx recipients using flow cytometric analysis. The post-transplant CD25highCD127-CD4+ Treg cells in KTx recipients were down-regulated compared with those of healthy volunteers (P < .001). Among them, 11 KTx recipients showed dnDSA formation, which was associated with lower frequencies of CD25highCD127-CD4+ Treg cells (P = .040). Furthermore, of the total Treg cell population, CD45RA-CD25highCD127-CD4+ activated Treg (aTreg) cells were significantly dominant in patients with dnDSA (P = .038), but not CD45RA+CD25highCD127-CD4+ resting Treg cells (P = .961). In contrast, non-donor-specific anti-HLA antibody formation was not associated with CD45RA- aTreg cells (P = .772). Multivariate logistic regression analyses revealed that CD45RA- aTreg cells were independently associated with dnDSA formation (Odds ratio = 6.69, P = .040). These findings indicate that CD45RA- aTreg cells are strongly associated with dnDSA formation in KTx recipients and might be an important risk factor of antibody-mediated rejection before clinical diagnosis.