Evidence of a novel galectin-9-binding membrane glycoprotein ligand on T helper cells

An update on potentials and promises of T cell co-signaling molecules in transplantation

The promising outcomes of immune-checkpoint based immunotherapies in cancer have provided a proportional perspective ahead of exploiting similar approaches in allotransplantation. Belatacept (CTLA-4-Ig) is an example of costimulation blockers successfully exploited in renal transplantation. Due to the wide range of regulatory molecules characterized in the past decades, some of these molecules might be candidates as immunomodulators in the case of tolerance induction in transplantation. Although there are numerous attempts on the apprehension of the effects of co-signaling molecules on immune response, the necessity for a better understanding is evident. By increasing the knowledge on the biology of co-signaling pathways, some pitfalls are recognized and improved approaches are proposed. The blockage of CD80/CD28 axis is an instance of evolution toward more efficacy. It is now evident that anti-CD28 antibodies are more effective than CD80 blockers in animal models of transplantation. Other co-signaling axes such as PD-1/PD-L1, CD40/CD154, 2B4/CD48, and others discussed in the present review are examples of critical immunomodulatory molecules in allogeneic transplantation. We review here the outcomes of recent experiences with co-signaling molecules in preclinical studies of solid organ transplantation.

Galectin-9 in Combination With EX-527 Prolongs the Survival of Cardiac Allografts in Mice After Cardiac Transplantation

Galectin-9 (Gal-9), a member of the galectin family, has a variety of biologic activities. However, its role in allografts is not fully clarified yet. The relationship between interleukin-17 (IL-17) and Gal-9 and the role of Gal-9 in T(H)17-cell differentiation also remain unclear. We built a murine cardiac transplantation model, which we treated with Gal-9 and/or EX-527, a specific Sirtuin-1 inhibitor. Afterwards, flow-cytometric analysis and reverse-transcription polymerase chain reaction were used to detect the number of T(H)17 cells and the expression of key factors involved in the differentiation of T(H)17 cells; in addition, the survival times of cardiac transplanted mice in different groups were recorded. The levels of circulating T(H)17 cells were found to increase in the peripheral blood of mice that exhibited acute rejection (AR) after heart transplantation, which was determined to be correlated with the rejection grade. Gal-9 or EX-527 can inhibit the activation and differentiation of T(H)17 cells and effectively suppress T(H)17-cell-mediated AR. These data provide new evidence for the potential regulatory effects of Gal-9 in alloimmune responses in a murine model of heart transplantation, and suggest the combined use of galectin-9 and EX-527 may be a powerful method to induce tolerance of fully mismatched murine cardiac allografts.

Expression of coinhibitory receptors on T cells in the microenvironment of usual vulvar intraepithelial neoplasia is related to proinflammatory effector T cells and an increased recurrence-free survival

Human papillomavirus-induced usual-type vulvar intraepithelial neoplasia (uVIN) are infiltrated by immune cells but apparently not cleared. A potential explanation for this is an impaired T cell effector function by an immunesuppressive milieu, coinfiltrating regulatory T cells or the expression of coinhibitory molecules. Here, the role of these potential inhibitory mechanisms was evaluated by a detailed immunohistochemical analysis of T cell infiltration in the context of FoxP3, Tbet, indoleamine 2,3-dioxygenase, programmed cell death 1, T cell immunoglobulin mucin 3 (TIM3), natural killer cell lectin-like receptor A (NKG2A) and galectins-1, -3 and -9. Paraffin-embedded tissues of primary uVIN lesions (n=43), recurrent uVIN lesions (n=20), vulvar carcinoma (n=21) and healthy vulvar tissue (n=26) were studied. We show that the vulva constitutes an area intensely surveyed by CD8+, CD4+, Tbet+ and regulatory T cell populations, parts of which express the examined coinhibitory molecules. In uVIN especially, the number of regulatory T cells and TIM3+ T cells increased. The expression of the coinhibitory markers TIM3 and NKG2A probably reflected a higher degree of T cell activation as a dense infiltration with stromal CD8+TIM3+ T cells and CD3+NKG2A+ T cells was related to the absence of recurrences and/or a prolonged recurrence-free survival. A dense coinfiltrate with regulatory T cells was negatively associated with the time to recurrence, most dominantly when the stromal CD8+TIM3+ infiltration was limited. This notion was sustained in vulvar carcinoma's where the numbers of regulatory T cells progressively increased to outnumber coinfiltrating CD8+TIM3+ T cells and CD3+NKG2A+ T cells.

Up-regulation of Galectin-9 in vivo results in immunosuppressive effects and prolongs survival of liver allograft in rats

BACKGROUND AND OBJECTIVE

Acute rejection is still a major cause of graft dysfunction and would jeopardize recipients' post-transplantation survival. Current studies demonstrate that Galectin-9 (Gal-9) is associated with down-regulation of pro-inflammatory cytokines, thus, possesses a negative immune regulatory role. However, the specific role of Gal-9 in liver transplant remains unknown.

METHODS

To establish acute rejection models of rat liver transplantation (Lewis-BN, n = 45), recipients were randomly divided into following three groups: the transfected group (n = 15); the blank plasmid group (n = 15); and the control group (n = 15). The transfected group was perfused with Ad-galectin-9 through the portal vein during the cold ischemia period. The blank plasmid group was perfused with non-target vector, and the control group was perfused with saline. The acute rejection was assayed by pathological examination; Gal-9, T-bet, RORγt, GATA3 and Foxp3 mRNA expression was detected by real-time PCR; Western blots and enzyme-linked immunosorbent assays were performed to measure IFN-γ, IL-10 and IL-17 expression.

RESULTS

The pathological change of the transfected group was ameliorated than that of the other two groups. The Gal-9 mRNA level in the transfected group was much higher than that in the other two groups (*P < 0.05); T-bet and RORγt mRNA levels were significantly lower in the transfected group than in the other two groups while GATA3 and Foxp3 were not shown statistics significances (*P < 0.05). The IFN-γ and IL-17 levels in the transfected group were significantly lower than in the other two groups (*P < 0.05 for both protein and serum levels).

CONCLUSION

Up-regulation of Gal-9 in vivo turns immune system toward immnuosuppression and prolongs rats liver allograft survival by the diminishment of Th1/Th17.

Proinflammatory stimuli induce galectin-9 in human mesenchymal stromal cells to suppress T-cell proliferation

Human multipotent mesenchymal stromal cells (MSCs) are clinically applied to treat autoimmune diseases and graft-versus-host disease due to their immunomodulatory properties. Several molecules have been identified to mediate these effects, including constitutively expressed galectin-1. However, there are indications in the literature that MSCs exert enhanced immunosuppressive functions after interaction with an inflammatory environment. Therefore, we analyzed how inflammatory stimuli influence the expression of the galectin network in MSCs and functionally tested the relevance for the immunomodulatory effects of MSCs. We found that galectin-9 was strongly induced in MSCs upon interaction with activated PBMCs. Proinflammatory cytokines, such as interferon-gamma (IFN-γ) and tumor necrosis factor-alpha (TNF-α), and also ligands of the Toll-like receptors (TLRs) TLR2, TLR3, and TLR4 elicited similar induction of galectin-9 in activated PBMCs. Galectin-9 was not only upregulated intracellularly, but also released by MSCs in significant amounts into the supernatant after exposure to proinflammatory stimuli. In proliferation assays, MSCs with a galectin-9 knockdown lost a significant portion of their antiproliferative effects on T cells. In conclusion, we found that unlike constitutively expressed galectin-1, galectin-9 is induced by several proinflammatory stimuli and released by MSCs. Thus, galectin-9 contributes to the inducible immunomodulatory functions of MSCs.