Suppressive activity and regulatory T-cell phenotypes of cells generated from human peripheral blood mononuclear cells under CD80/CD86 costimulation blockade.

BACKGROUND

Costimulation blockade targeting CD80/CD86 has been widely investigated as an immunomodulatory strategy in transplantation. However, its effects on human peripheral immune cells and the induction of regulatory phenotypes remain incompletely understood.

METHODS

Human peripheral blood mononuclear cells (PBMCs) were cultured under CD80/CD86 costimulation blockade. Suppressive activity was evaluated using mixed lymphocyte reactions (MLRs). The contribution of T cells was assessed by CD3 depletion and reconstitution experiments. Regulatory T-cell phenotypes and cytokine production were analyzed by flow cytometry.

RESULTS

Cells generated under CD80/CD86 costimulation blockade suppressed MLR responses in a dose-dependent manner. Following depletion of CD3+ cells, relative proliferation returned to near-control levels, whereas reconstitution of CD3+ cells restored the suppressive pattern, findings consistent with a contribution of CD3+ T cells. Phenotypic analysis revealed increased frequencies of CD4+CD25+Foxp3+, CD4+CD25+CTLA-4+, and CD4+CD127lowFoxp3+ regulatory T-cell populations. IL-10-producing T cells also increased after culture, with prominent expression in the CD4+CD8+ double-positive subset.

CONCLUSIONS

Cells generated from human PBMCs under CD80/CD86 costimulation blockade exhibited suppressive activity, and the depletion and reconstitution findings were consistent with a contribution of CD3+ T cells. These cells showed increased frequencies of cells with regulatory T-cell phenotypes and of IL-10-producing T-cell subsets relative to freshly isolated PBMCs. These findings further characterize the immunomodulatory properties of human PBMC-derived cells generated under CD80/CD86 costimulation blockade.