Wei-ping Zheng

Differentiation of Th cells from naive precursors is a dynamic process that involves multiple transcription factors acting at specific time points to regulate gene expression. In this study we show that the homeobox transcription factor Hlx is up-regulated early in Th1 cell differentiation. Mice constitutively expressing an Hlx transgene driven by a CD4 promoter showed marked reduction in the CD4+CD8+ thymocyte population. The Hlx transgenic mice generated increased numbers of Th1 cells in response to keyhole limpet hemocyanin immunization. After differentiation under Th2-polarizing conditions in vitro, the transgenic CD4 T cells expressed high levels of IFN-gamma. Intracellular cytokine staining revealed that in addition to Th2 cells, large numbers of Th0 and Th1 cells were generated from such in vitro differentiated transgenic CD4 T cells. Retrovirally overexpressed Hlx also induced the aberrant expression of IFN-gamma in normal CD4 T cells differentiated under Th2-polarizing conditions. This effect was apparent only when Hlx was introduced into the cells by retroviral infection at an early time point that led to the expression of the retrovirally transferred Hlx gene at a time comparable to that of the up-regulation of the endogenous Hlx during Th1 cell differentiation. Later infection with Hlx-expressing retrovirus showed no effect. Thus, the induction of IFN-gamma expression by Hlx depends on a permissive epigenetic state of the IFN-gamma gene locus and/or the molecular context of the immature Th cells.

The intrinsic features of naive CD4 T cells that affect their ability to respond to polarizing signals for Th cell differentiation are not well understood. In this study, we show that naive CD4 T cells from mice transgenic for the Hlx gene expressed lower levels of IL-4Ralpha. The down-regulation of IL-4Ralpha diminished IL-4 signaling and the Th2 response and enhanced the Th1 response under suboptimal polarizing conditions. In nontransgenic CD4 T cells, blocking IL-4Ralpha with Abs had the same effect in an Ab dose-dependent manner. Conversely, Hlx haploinsufficiency caused higher expression of IL-4Ralpha to favor Th2 cell differentiation. Thus, the IL-4Ralpha level on naive CD4 T cells is genetically controlled by Hlx and determines the ratio of Th1 and Th2 cell differentiation.

BACKGROUND: Liver transplantation (LT) is required in many end-stage liver diseases. Donation after cardiac death (DCD) livers are often used, and treatment of acute rejection (ACR) requires the use of immunosuppressive drugs that are associated with complications. Bone marrow mesenchymal stem cells (BMMSCs) are used in treatment following LT; however, they have limitations, including low colonization in the liver. An optimized BMMSC application method is required to suppress ACR. METHODS: BMMSCs were isolated and modified with the heme oxygenase 1 (HO-1) gene. HO-1/BMMSCs were perfused into donor liver in vitro using a normothermic machine perfusion (NMP) system, followed by LT into rats. The severity of ACR was evaluated based on liver histopathology. Gene chip technology was used to detect differential gene expression, and flow cytometry to analyze changes in natural killer (NK) T cells. RESULTS: NMP induced BMMSCs to colonize the donor liver during in vitro preservation. The survival of HO-1/BMMSCs in liver grafts was significantly longer than that of unmodified BMMSCs. When the donor liver contained HO-1/BMMSCs, the local immunosuppressive effect was improved and prolonged, ACR was controlled, and survival time was significantly prolonged. The application of HO-1/BMMSCs reduced the number of NKT cells in liver grafts, increased the expression of NKT cell co-inhibitory receptors, and reduced NKT cell expression of interferon-γ. CONCLUSIONS: T cell activation was inhibited by application of HO-1/BMMSCs, which reduced ACR of transplanted liver. This approach could be developed to enhance the success rate of LT.