Th17-Related Gene Rorγt Overexpressed in Patients with Chronic Gvhd: New Insights for T-Cell Manipulation and Gvhd Control

Introduction: Graft-versus-host disease (GVHD) is on of the leading complication of allogeneic hematopoietic stem cell transplantation (HSCT)  causing significant morbidity and mortality. CD4+ T-cells play a critical role in mediating GVHD, and much effort has been devoted to studying the effect of CD4+ T-cells during the pathophysiology process of GVHD. Even though just accounting for 5% of the total CD4⁺ T-cell population, the most promising candidates are naturally occurring CD4+CD25+ regulatory T cells (T_regs), which are on of the regulators of immune responses. TH₁₇ is a newly identified T-cell lineage that secretes IL-17, a proinflammatory cytokine. However, the functional role of TH₁₇ cells in the development of GVHD has not been well characterized in humans. The aim of our study was to characterize the expression of T_reg (FOXP3) and TH₁₇-related (RORγt) genes in peripheral blood of patients undergoing HSCT and correlate them with the development of GVHD in HLA identical allogeneic HSCT. Patients and Methods: Samples were collected from peripheral blood of 50 patients before and after HSCT and at the time of GVHD onset. Thirty patients were diagnosed as acute leukemia/myelodysplastic syndrome, eleven as chronic myeloid leukemia and ten with lymphomas. Seven healthy donors were used as controls. All patients received HLA-identical related donor graft. Except for lymphomas patients (n=10), who underwent non-myeloablative conditioning, others underwent myeloablative conditioning regimens (n=40). Expression of FOXP3 and RORγt were assessed by Real-Time quantitative PCR (qPCR) using the 7500 Fast Real Time PCR System (Applied Biosystems), by Taqman method. Comparison among groups was performed using Graphpad Prism 5 and Mann-Withney test. Results: Median age for the 50 analyzed patients was 36 years-old (range: 17-60), 52% were female. 50% had GVHD, with an average onset of 39 days after HSCT for acute GVHD (range: 12-93) and 182 days for chronic GVHD (range: 117-266). No significant association was observed between FOXP3 expression and patients with or without GVHD. On the other hand, RORγt showed significantly higher expression in patients with chronic GVHD compared to samples before HSCT (p<0.0001), without GVHD (p<0.0001) and acute GVHD (p=0.0006). Both FOXP3 and RORγt showed significant statistical decreased expression in patients compared to healthy controls, except for RORγt expression in patients with chronic GVHD (p=NS). Conclusion: RORγtshowed significantly higher expression in patients with chronic GVHD compared to samples before HSCT, without GVHD and acute GVHD. These findings suggest a Th17/IL-17 mediated proinflammatory state involved in chronic GVHD, showing a potential target for GVHD control. Disclosures: No relevant conflicts of interest to declare.