CD45RA distinguishes CD4+CD25+CD127-/low TSDR demethylated regulatory T cell subpopulations with differential stability and susceptibility to tacrolimus mediated inhibition of suppression.

Background: Adoptive transfer of FOXP3+ regulatory T cells (Treg) offers a promising strategy to reduce damage to an allograft by the recipient's immune system. Identification of cell surface markers sufficient to purify Treg expanded ex vivo to remove cellular contaminants requires optimisation. Furthermore, the expanded Treg must be able to survive, expand and suppress in allograft recipients exposed to immunosuppressants such as tacrolimus (TAC). Reduced CD127 expression enhances identification of Treg in the human CD4+CD25+ population. CD45RA expression identifies naive CD4+CD25+ Treg with an enhanced stability of Treg phenotype. Methods: We combine an analysis of CD45RA, CD25 and CD127 expression to identify subpopulations of CD4+CD127-/loCD25+ cells. Treg were sorted according to expression of CD25 and CD45RA and expanded in the presence of a physiological relevant concentration of tacrolimus. TSDR demethylation, FOXP3 expression and suppression were analysed. Results: CD4+CD127-/loCD25+CD45RA+ Treg had a stable TSDR demethylated FOXP3+ phenotype following expansion whilst CD4+CD127lo/-CD25+CD45RA- Treg lost the TSDR demethylated phenotype. CD45RA- Treg had a greater capacity to suppress following expansion with tacrolimus. Conclusions: Although CD45RA- Treg retained a greater suppressive capacity when expanded with TAC, the marked loss of the TSDR demethylated status highlights the potential for loss of stability of these cells in transplant recipients treated with TAC based immunosuppression. We show that a population of CD4+CD127-/loCD45RA+ Treg may offer the best compromise between susceptibility to loss of suppression when exposed to TAC and maintenance of a TSDR demethylated phenotype following in vitro expansion. This is an open access article distributed under the Creative Commons Attribution License 4.0 (CCBY), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Copyright (C) 2016 Wolters Kluwer Health, Inc. All rights reserved.

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