Yuri Futagami

Retinal Pigment Epithelium-Derived CTLA-2α Induces TGFβ-Producing T Regulatory Cells

T cells that encounter ocular pigment epithelium in vitro are inhibited from undergoing TCR-triggered activation, and instead acquire the capacity to suppress the activation of bystander T cells. Because retinal pigment epithelial (RPE) cells suppress T cell activation by releasing soluble inhibitory factors, we studied whether soluble factors also promote the generation of T regulatory (Treg) cells. We found that RPE converted CD4+ T cells into Treg cells by producing and secreting CTLA-2α, a cathepsin L (CathL) inhibitor. Mouse rCTLA-2α converted CD4+ T cells into Treg cells in vitro, and CTLA-2α small interfering RNA-transfected RPE cells failed to induce the Treg generation. RPE CTLA-2α induced CD4+CD25+Foxp3+ Treg cells that produced TGFβ in vitro. Moreover, CTLA-2α produced by RPE cells inhibited CathL activity in the T cells, and losing CathL activity led to differentiation to Treg cells in some populations of CD4+ T cells. In addition, T cells in the presence of CathL inhibitor increased the expression of Foxp3. The CTLA-2α effect on Treg cell induction occurred through TGFβ signaling, because CTLA-2α promoted activation of TGFβ in the eye. These results show that immunosuppressive factors derived from RPE cells participate in T cell suppression. The results are compatible with the hypothesis that the eye-derived Treg cells acquire functions that participate in the establishment of immune tolerance in the posterior segment of the eye.

T-cell suppression by programmed cell death 1 ligand 1 on retinal pigment epithelium during inflammatory conditions.

PURPOSE To determine whether retinal pigment epithelial (RPE) cells can inhibit in vitro T-cell activation during inflammatory conditions. METHODS Primary cultured RPE cells were established from normal C57BL/6 mice. Target bystander T cells were established from normal splenic T cells with anti-CD3 antibodies. T-cell activation was assessed for proliferation by both examining [(3)H]-thymidine incorporation and the production of interferon (IFN)gamma or IL-17, as determined by ELISA. Expression of programed cell death 1 ligand 1 (PD-L1) on RPE or recombinant mouse IFNgamma-pretreated RPE cells was evaluated using oligonucleotide microarray, RT-PCR, immune staining, and flow cytometry. Expression of programed cell death 1 (PD-1)(+) on target T cells was evaluated by flow cytometry. Anti-mouse PD-L1 or PD-L2 neutralizing antibodies or target T cells from PD-1 knockout donors were used for the assay. RESULTS IFNgamma-pretreated RPE greatly suppressed activation of bystander T cells, especially the IFNgamma production by the target T cells (Th1 cells, but not Th17 cells) via direct cell contact. By examining cell surface candidate molecules, IFNgamma-pretreated RPE expressed much higher levels of PD-L1 compared with the control nontreated RPE. Although primary RPE did not express the costimulatory molecule, expression of the molecule was induced on the surface of IFNgamma-pretreated RPE. PD-L1(+) RPE in the presence of IFNgamma selectively suppressed PD-1(+) T-cell activation. IFNgamma-pretreated RPE in the presence of anti-PD-L1 neutralizing antibodies, but not anti-PD-L2, failed to suppress T-cell production of IFNgamma. In addition, these RPE cells failed to suppress the production of IFNgamma by CD4(+) T cells from PD-1 null donors. CONCLUSIONS Suppression of T-cell activation was obtained in cultures only when RPE expressed negative costimulators. Therefore, the authors propose that in vitro, Th1 cytokine-exposed ocular resident cells can express this molecule and it is this expression that causes the suppression of the bystander Th1-type cells.

Role of Thrombospondin-1 in T Cell Response to Ocular Pigment Epithelial Cells

Ocular pigment epithelium (PE) cells promote the generation of T regulators (PE-induced Treg cells). Moreover, T cells exposed to PE acquire the capacity to suppress the activation of bystander T cells via TGFβ. Membrane-bound TGFβ on iris PE cells interacts with TGFβ receptors on T cells, leading to the conversion of T cells to CD8+ Treg cells via a cell contact-dependent mechanism. Conversely, soluble forms of TGFβ produced by retinal PE cells can convert CD4+ T cells into Treg cells in a manner that is independent of cell contact. In this study, we looked at the expression of immunoregulatory factors (TGFβ, thrombospondins, CD59, IL-1 receptor antagonist, etc.) in PE cells as identified via an oligonucleotide microarray. Several thrombospondin-binding molecules were detected, and thus we focused subsequent analyses on thrombospondins. Via the conversion of latent TGFβ to an active form that appears to be mediated by thrombospondin 1 (TSP-1), cultured iris PE and retinal PE cells induce a PE-induced Treg cell fate. After conversion, both ocular PE and PE-induced Treg cells express TSP-1. Regulatory T cell generation was amplified when the T cells also expressed TSP-1. In addition, PE-induced Treg cells significantly suppressed activation of bystander T cells via TSP-1. These results strongly suggest that the ability of ocular PE and PE-induced Treg cells to suppress bystander T cells depends on their capacity to produce TSP-1. Thus, intraocular TSP-1 produced by both ocular parenchymal cells and regulatory T cells is essential for immune regulation in the eye.

Human Corneal Endothelial Cells Expressing Programmed Death-Ligand 1 (PD-L1) Suppress PD-1+ T Helper 1 Cells by a Contact-Dependent Mechanism

PURPOSE This study was designed to determine whether human corneal endothelial (HCE) cells could regulate the activation of bystander T cells in vitro. METHODS HCE cell lines were established from primary HCE cells. Target-activated T cells were used allogeneic T cells and Jurkat T-cell lines. As an additional target, T-cell clones from uveitis patients were established from aqueous humor via a limiting dilution. T-cell activation was assessed for proliferation by [(3)H]-thymidine incorporation, carboxyfluorescein succinimidyl ester incorporation, or IFNgamma production. Expression of co-stimulatory molecules on IFNgamma-treated corneal endothelial and non-treated cells was evaluated by flow cytometry, RT-PCR, or immunohistochemistry. Expression of co-stimulatory receptors on target T cells was evaluated by flow cytometry. Blocking antibodies was used to abolish the HCE-inhibitory function. RESULTS HCE cells suppressed both in vitro proliferation and IFNgamma production by CD4(+) T cells via a cell contact-dependent mechanism. HCE constitutively expressed co-stimulatory molecules programmed death-ligand 1 (PD-L1) and PD-L2, and their expression was enhanced by IFNgamma. HCE efficiently inhibited the proliferation of Th1 cells that overexpressed PD-1 among various activated T-cell lines and clones established from patients with uveitis or corneal endotheliitis. A neutralizing mAb for PD-L1, but not PD-L2, blocked the suppressive effect of HCE on Th1 cells. CONCLUSIONS HCE can impair the effector functions and activation of Th1 infiltrating CD4(+) T cells via the PD-1/PD-L1 interaction. The data support the hypothesis that corneal endothelium may contribute to maintenance of the privileged immune status of the anterior chamber of the eye by inducing peripheral immune tolerance.

Human retinal pigment epithelium-induced CD4+CD25+ regulatory T cells suppress activation of intraocular effector T cells

Murine retinal pigment epithelial (RPE) cells suppress T-cell activation by releasing soluble inhibitory factors and promote the generation of regulatory T cells in vitro. These T cells exposed to RPE supernatants (RPE-induced Treg cells) can suppress the activation of bystander effector T cells via the production of transforming growth factor-beta (TGFbeta). In the present study, we showed that human RPE-induced Treg cells are also able to acquire regulatory function when human RPE cell lines were pretreated with recombinant TGF beta 2. These RPE-induced Treg cells produced TGF beta 1 and IL-10 but not IFN gamma, and they significantly suppressed the activation of target cell lines and intraocular T-cell clones established from patients with active uveitis. Moreover, CD4(+)CD25(+) RPE-induced Treg cells expressed CTLA-4 and Foxp3 molecules, and the CD25(+) Treg cells profoundly suppressed the T-cell activation. Thus, in vitro manipulated Treg cells acquire functions that participate in the establishment of immune tolerance in the eye.

Human iris pigment epithelium suppresses activation of bystander T cells via TGFβ–TGFβ receptor interaction

Iris pigment epithelial (IPE) cells from the anterior segment in the eye are able to suppress activation of bystander responder T cells in vitro. The cultured IPE cells fully suppress proliferation and cytokine production by responder T cells via direct cell-to-cell contact. We have now investigated whether primary cultured human iris pigment epithelial (h-IPE) cells that were established from fresh iris tissues can also inhibit the activation of T cells in vitro. We found that cultured h-IPE cells significantly inhibited T cell proliferation and the IFN-gamma production by the target T cells from both the allogeneic and autogeneic peripheral blood mononuclear cells (PBMCs). The h-IPE cells also inhibited the activation of CD4(+) T cells from patients with active uveitis. The suppression by h-IPE occurred in a completely contact-dependent manner. The h-IPE constitutively expressed transforming growth factor beta (TGFbeta) and the receptors, and the T cells exposed to h-IPE greatly expressed Smad transcripts. In addition, TGFbeta2-siRNA transfected h-IPE failed to inhibit activation of responder T cells. Similarly, h-IPE cells in the presence of anti-TGFbeta neutralizing antibodies or recombinant TGFbeta receptor blocking proteins failed to inhibit the T-cell activation. In conclusion, cultured human iris pigment epithelium fully inhibits T cell activation in vitro. Our data support the hypothesis that the ocular resident cells play a critical role in immunosuppression in the eye.

Bilateral Anterior Granulomatous Keratouveitis with Sunset Glow Fundus in a Patient with Autoimmune Polyglandular Syndrome

Aim: To report the case of a patient with bilateral anterior granulomatous keratouveitis and sunset glow fundus. Method: Review of case record. Results: A 15-year-old patient had bilateral anterior granulomatous keratouveitis and sunset glow fundus similar to findings in Vogt-Koyanagi-Harada disease (VKH). However, the patient also suffered additional autoimmune disease against endocrine glands. In addition to anti-thyroid antibody and anti-glutamic acid decarboxylase antibody, anti-melanocyte autoantibody was detected in serum from this patient. The authors finally diagnosed autoimmune polyglandular syndrome. Conclusion: If resistance against treatment exists for VKH, particularly in pediatric cases, this disease should be considered and other endocrine disorders examined.