An orchestrated dance between differing regulatory T cell phenotypes in allograft tolerance

Clinical significance of CCR7+CD8+ T cells in kidney transplant recipients with allograft rejection

The regulatory function of CCR7⁺CD8⁺ T cells against effector T-cells involved in T-cell mediated rejection (TCMR) in kidney transplant recipients was investigated. In vitro experiments explored the ability of CCR7⁺CD8⁺ T cells to suppress T-cell proliferation under T-cell activation conditions or during coculture with human renal proximal tubular epithelial cells (HRPTEpiC). In an ex vivo experiment, the proportion of CCR7⁺/CD8⁺, FOXP3⁺/CCR7⁺CD8⁺ T and effector T-cell subsets were compared between the normal biopsy control (NC, n = 17) and TCMR group (n = 17). The CCR7⁺CD8⁺ T cells significantly suppressed the proliferation of CD4⁺ T cells and significantly decreased the proportion of IFN-γ⁺ and IL-17⁺/CD4⁺ T cells and inflammatory cytokine levels (all p < 0.05). After coculturing with HRPTEpiC, CCR7⁺CD8⁺ T cells also suppressed T-cell differentiation into IL-2⁺, IFN-γ⁺, and IL-17⁺/CD4⁺ T cells (all p < 0.05). The TCMR group had significantly fewer CCR7⁺/CD8⁺ and FOXP3⁺/CCR7⁺CD8⁺ T in comparison with the NC group, but the proportions of all three effector T-cell subsets were increased in the TCMR group (all p < 0.05). The proportion of CCR7⁺/CD8⁺ T was inversely correlated with those of effector T-cell subsets. The results indicate that CCR7⁺CD8⁺ T cells may regulate effector T-cells involved in TCMR in an in vitro and in an ex vivo transplant model.

Human CD45RA(-) FoxP3(hi) Memory-Type Regulatory T Cells Show Distinct TCR Repertoires With Conventional T Cells and Play an Important Role in Controlling Early Immune Activation

Adoptive immunotherapy with regulatory T cells (Treg) is a new option to promote immune tolerance following solid organ transplantation (SOT). However, Treg from elderly patients awaiting transplantation are dominated by the CD45RA(-) CD62L(+) central memory type Treg subset (TregCM), and the yield of well-characterized and stable naïve Treg (TregN) is low. It is, therefore, important to determine whether these TregCM are derived from the thymus and express high stability, suppressive capacity and a broad antigen repertoire like TregN. In this study, we showed that TregCM use a different T cell receptor (TCR) repertoire from conventional T cells (Tconv), using next-generation sequencing of all 24 Vβ families, with an average depth of 534 677 sequences. This showed almost no contamination with induced Treg. Furthermore, TregCM showed enhanced suppressive activity on Tconv at early checkpoints of immune activation controlling activation markers expression and cytokine secretion, but comparable inhibition of proliferation. Following in vitro expansion under mTOR inhibition, TregCM expanded equally as well as TregN without losing their function. Despite relatively limited TCR repertoire, TregCM also showed specific alloresponse, although slightly reduced compared to TregN. These results support the therapeutic usefulness of manufacturing Treg products from CD45RA(-) CD62L(+) Treg-enriched starting material to be applied for adoptive Treg therapy.