Invariant natural killer T cells infiltrate intestinal allografts undergoing acute cellular rejection

Dysregulated Peripheral Invariant Natural Killer T Cells in Plaque Psoriasis Patients

Background: Psoriasis is a common immune-mediated skin disease that involves T-cell-mediated immunity. Invariant natural killer T (iNKT) cells are a unique lymphocyte subpopulation that share properties and express surface markers of both NK cells and T cells. Previous reports indicate that iNKT cells regulate the development of various inflammatory diseases. IL-17 is a key cytokine in the pathogenesis of psoriasis and a key therapeutic target. Secukinumab is a fully human IgG1κ antibody that targets IL-17A, thereby antagonizing the biological effects of IL-17.

Objective: To explore the expression of iNKT cells in psoriasis patients and the effect of secukinumab on them.

Methods: We examined the frequencies of iNKT cells, Tregs, naïve and memory CD4⁺and CD8⁺T cells in the PBMCs as well as their cytokine production in a cohort of 40 patients with moderate-to-severe plaque psoriasis and 40 gender- and age-matched healthy controls. We further collected peripheral blood of another 15 moderate-to-severe plaque psoriasis patients who were treated with secukinumab and evaluated the proportion of iNKT cells in the PBMCs at baseline and week 12.

Results: The frequencies of conventional CD4⁺ T cells, CD8⁺ T cells, and Tregs in the PBMCs were comparable between psoriasis patients and healthy controls, but the frequencies of Th17 cells, Tc1 cells and Tc17 cells were increased in psoriasis patients. The frequency of peripheral iNKT cells and CD69⁺iNKT cells was significantly decreased in psoriasis patients. Both iNKT2 cells and iNKT17 cells were increased in psoriasis patients, but the ratio of iNKT2 cells vs iNKT17 cells was significantly reduced in psoriasis patients. After receiving secukinumab, the proportion of iNKT cells in the PBMCs of patients was increased, while the proportion of iNKT17 cells was decreased.

Conclusion: Dysregulated iNKT cells may be involved in the pathogenesis of psoriasis and secukinumab may play a regulatory role on iNKT cells.

Recombinant HLA-G as Tolerogenic Immunomodulant in Experimental Small Bowel Transplantation

The non-classical MHC I paralogue HLA-G is expressed by cytotrophoblast cells and implicated with fetomaternal tolerance by downregulating the maternal adaptive and innate immune response against the fetus. HLA-G expression correlates with favorable graft outcome in humans and recently promising immunosuppressive effects of therapeutic HLA-G in experimental transplantation (skin allograft acceptance) were shown. Consequently, we examined this novel therapeutic approach in solid organ transplantation. In this study, therapeutic recombinant HLA-G5 was evaluated for the first time in a solid organ model of acute rejection (ACR) after orthotopic intestinal transplantation (ITX). Allogenic ITX was performed in rats (Brown Norway to Lewis) with and without HLA-G treatment. It was found that HLA-G treatment significantly reduced histologically proven ACR at both an early and late postoperative timepoint (POD 4/7), concomitant to a functionally preserved graft contractility at POD 7. Interestingly, graft infiltration by myeloperoxidase+ cells was significantly reduced at POD7 by HLA-G treatment. Moreover, HLA-G treatment showed an effect on the allogenic T-cell immune response as assessed by flow cytometry: The influx of recipient-derived CD8⁺ T-cells into the graft mesenteric lymphnodes at POD7 was significantly reduced while CD4⁺ populations were not affected. As a potential mechanism of action, an induction of T-reg populations in the mesenteric lymphnodes was postulated, but flow cytometric analysis of classical CD4⁺/CD25⁺/FoxP3⁺T_reg-cells showed no significant alteration by HLA-G treatment. The novel therapeutic approach using recombinant HLA-G5 reported herein demonstrates a significant immunosuppressive effect in this model of allogenic experimental intestinal transplantation. This effect may be mediated via inhibition of recipient-derived CD8⁺ T-cell populations either directly or by induction of non-classical T_reg populations.

Tolerogenic Dendritic Cells on Transplantation: Immunotherapy Based on Second Signal Blockage

Dendritic cells (DCs), the most important professional antigen-presenting cells (APC), play crucial role in both immunity and tolerance. It is well known that DCs are able to mount immune responses against foreign antigens and simultaneously tolerate self-antigens. Since DCs can be modulated depending on the surrounding microenvironment, they can act as a bridge between innate and adaptive immunity. However, the mechanisms that support this dual role are not entirely clear. Recent studies have shown that DCs can be manipulated ex vivo in order to trigger their tolerogenic profile, what can be a tool to be used in clinical trials aiming the treatment of various diseases and the prevention of transplant rejection. In this sense, the blockage of costimulatory molecules on DC, in the attempt of inhibiting the second signal in the immunological synapse, can be considered as one of the main strategies under development. This review brings an update on current therapies using tolerogenic dendritic cells modulated with costimulatory blockers with the aim of reducing transplant rejection. However, although there are current clinical trials using tolerogenic DC to treat allograft rejection, the actual challenge is to modulate these cells in order to maintain a permanent tolerogenic profile.