Renal Transplant Recipients Treated with Calcineurin-Inhibitors Lack Circulating Immature Transitional CD19+CD24hiCD38hi Regulatory B-Lymphocytes

Abstract

BackgroundCD19+CD24hiCD38hi transitional immature B-lymphocytes have been demonstrated to play an important role in regulating the alloimmune response in transplant recipients. Here, we analyzed the effect of calcineurin inhibition on these peripherally circulating regulatory B-cells (Breg) in renal transplant recipients receiving cyclosporine A (CsA) or tacrolimus.MethodsPBMCs from healthy subjects (HS) (n = 16) and renal transplant recipients (n = 46) were isolated. Flow cytometry was performed for CD19, CD24, CD38 and IL-10 either after isolation or after 72 hours of co-culture in presence of PMA/Ionomycin and TLR9-ligand in presence or absence of increasing concentrations of tacrolimus or CsA.ResultsThe amount of CD19+ B-cells among lymphocytes was ∼9.1% in HS, ∼3.6% in CsA (n = 11, p<0.05) and ∼6.4% in TAC (n = 35, p<0.05) treated patients. Among B-cells, a distinct subset of Breg was found to be 4.7% in HS, 1.4% in tacrolimus treated patients and almost blunted in patients receiving CsA. Similarily, ∼4% of B-cells in HS and even fewer in CsA or tacrolimus treated patients produced IL-10 (0.5% and 1.5%, p<0.05) and this was confirmed both in non-transplanted CsA-treated healthy subjects and in in vitro co-culture experiments. Among 29 patients with <1% of Breg, 9 cases (31%) displayed an allograft rejection in contrast to only one case of rejection (6%) among 17 patients with >1%.ConclusionCalcineurin inhibitors reduce number and IL-10 production of Bregs in the peripheral circulation of both renal transplant recipients and non-transplanted healthy subjects. CNI induced Breg reduction is not restricted to a solid organ transplant setting and is not mediated by co-medication with steroids or MPA. A low proportion of Breg cells is associated with an elevated frequency of allograft rejection events.

Regulatory B cells and advances in transplantation

“…In humans, the memory B10 subpopulation displaying the CD19 + CD24 hi CD27 + phenotype has been shown to suppress monocyte proinflammatory cytokines by producing IL‐10 in in vitro functional assays . The transitional B10 subpopulation with the CD19 + CD24 hi CD38 hi phenotype suppresses the differentiation of Th1 cells by producing IL‐10 after stimulation at the cell surface and signal activation . Unfortunately, at the moment, purification of B10 cells is technically challenging, which limits the in‐depth exploration of their functions.…”

A composite score associated with spontaneous operational tolerance in kidney transplant recipients

“…The “stable” population appears to be the most clinically relevant as future potential candidates for minimization protocols. Nevertheless, because immunosuppression has been shown to alter gene expression 41, 42, 52, 53 and particularly circulating B cells 54 , immunosuppression may affect cSoT. Unfortunately, samples before immunosuppression withdrawal are not available notably as TOL are mainly non-compliant and as intentional immunosuppression withdrawal trials have failed 18, 20 .…”

Transplantation tolerance: don't forget about the B cells

“…Tebbe et al . reported that calcineurin‐inhibitors in renal transplant recipients reduced the numbers of B cells, especially the immature transitional CD19 + CD24 hi CD38 hi regulatory B cells and IL‐10‐producing B cells. Rebollo‐Mesa et al .…”