Abstract
Purpose: :
Retinal pigment epithelium (RPE) cells are able to convert CD4+ T cells into T regulatory cells (Tregs) that greatly suppress bystander target T cells. In this study we designed to determine whether human RPE-induced Tregs can be expanded under Treg induction conditions and then, as RPE-induced Tregs, suppress activation of effector T cells.
Methods: :
Peripheral blood mononuclear cells from healthy donors were co-cultured with supernatants from TGFβ2-pretreated human RPE cells on anti-human CD3-coated plate. Cells were then separated with a CD4+CD25+ regulatory T-cell isolation kit, and cultured with the supernatants from RPE, anti-CD3, anti-CD28, high-dose recombinant IL-2, and TGFβ2. By flow cytometry sorting, CD25+CD45RA- Tregs were separated. Expression of CD25high, Foxp3, CD152 (CTLA-4), and TNFRSF 18 (GITR) on RPE-induced Tregs was analyzed by flow cytometry. Production of cytokines (TGFβ1, IL-10, IFNγ, IL-17, and TNFα) by RPE-induced Tregs was measured by ELISA. In addition, proliferation of target T cells (Th1/Th17 cell clines) was assessed by [3H]-thymidine incorporation or CFSE incorporation.
Results: :
RPE cells in the presence of TGFβ produce anti-inflammatory effects, and are able to induce Tregs in vitro. Human RPE-induced Tregs expressed higher levels of the Treg cell markers CD25high, Foxp3, CD152, and TNFRSF 18. In addition, human RPE-induced Tregs included significant numbers of CD4+CD25highFoxp3highCD45RA- active effector Tregs that significantly suppressed activation of Th1/Th17 cell lines, indicating that they have immunosuppressive properties. Furthermore, we are able to remove CD4+CD25lowFoxp3lowCD45RA- non-suppressing cytokine-secreting T cells from the in vitro-manipulated Treg population.
Conclusions: :
Present data provide hope that Tregs might become useful as individualized therapeutic agents for various ocular autoimmune diseases.
Keywords: retinal pigment epithelium • immune tolerance/privilege • inflammation