Human HLA-DR+CD27+ regulatory T cells show enhanced antigen-specific suppressive function

Area of Science:

• Immunology
• Cell Biology
• Transplantation Science

Background:

• Regulatory T cells (Tregs) are crucial for immune tolerance and preventing autoimmune diseases and graft rejection.
• Therapeutic Treg efficacy depends on antigen specificity and functional stability.
• Current Treg expansion methods need refinement to isolate stable, potent Treg subsets.

Purpose of the Study:

• To identify and isolate a distinct, functionally stable subset of human Tregs with therapeutic potential.
• To characterize the phenotype and function of xenoantigen-expanded Tregs (Xn-Tregs).
• To evaluate the efficacy of enriched Xn-Tregs in preventing xenogeneic islet graft rejection in a humanized mouse model.

Main Methods:

• Expansion of human Tregs using porcine peripheral blood mononuclear cells (PBMCs) to generate Xn-Tregs.
• Isolation of HLA-DR+CD27+ double-positive (DP) enriched Xn-Treg subset using cell sorting.
• Assessment of Treg phenotype (FOXP3, Helios, CD95, ICOS), demethylation status of the FOXP3 locus, and resistance to effector cell conversion.
• Functional assays including xenogeneic and polyclonal mixed lymphocyte reactions (MLRs).
• In vivo efficacy study involving adoptive transfer of enriched Xn-Tregs into a humanized mouse model of porcine islet transplantation.

Main Results:

• Xenoantigen expansion yielded a distinct Treg subset coexpressing HLA-DR and CD27, with an increased proportion of FOXP3+Helios+ Tregs.
• The HLA-DR+CD27+ DP-enriched Xn-Tregs exhibited upregulated Treg function markers (CD95, ICOS) and enhanced suppression of xenogeneic MLRs.
• These enriched Tregs showed reduced FOXP3 demethylation and greater resistance to conversion into effector cells.
• Adoptive transfer of DP-enriched Xn-Tregs significantly inhibited porcine islet graft rejection in a humanized mouse model, even with a high number of effector cells.
• Graft survival was linked to increased FOXP3+ Treg accumulation and expression of Treg functional genes (IL10, CTLA4) within the grafts, alongside downregulated effector cytokine genes.

Conclusions:

• Human HLA-DR+CD27+ DP-enriched Xn-Tregs possess a unique regulatory signature, identifying them as antigen-specific and functionally stable.
• This specific Treg subset demonstrates potent immunosuppressive capacity and efficacy in preventing xenogeneic graft rejection.
• These findings highlight the potential of HLA-DR+CD27+ DP-enriched Xn-Tregs as a promising cell-based therapy for autoimmune diseases and transplantation.