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CD4+ T cells not only direct immune responses against infectious micro-organisms but are also involved in the pathogenesis of inflammatory diseases. In the last two to three decades, various researchers have identified and characterized several functional CD4+ T-cell subsets, including T-helper 1 (Th1), Th2, Th9 and Th17 cells and regulatory T (Treg) cells. In this mini-review, we introduce the concept of pathogenic Th cells that induce inflammatory diseases with a model of disease induction by a population of pathogenic Th cells: the 'pathogenic Th population disease-induction model'. We will focus on Th2 cells that induce allergic airway inflammation—pathogenic Th2 cells (Tpath2 cells)—and discuss the nature of Tpath2 cells that shape the pathology of chronic inflammatory diseases. Various Tpath2-cell subsets have been identified and their unique features are summarized in mouse and human systems. Second, we will discuss how Th cells migrate and are maintained in chronic inflammatory lesions. We propose a model known as the 'CD69–Myl9 system'. CD69 is a cell surface molecule expressed on activated T cells and interaction with its ligand myosin light chain 9 (Myl9) is required for the induction of inflammatory diseases. Myl9 molecules in the small vessels of inflamed lungs may play a crucial role in the migration of activated T cells into inflammatory lesions. Emerging evidence may provide new insight into the pathogenesis of chronic inflammatory diseases and contribute to the development of new therapeutic strategies for intractable inflammatory disorders. [ABSTRACT FROM AUTHOR]

CD69 is a membrane molecule transiently expressed on activated lymphocytes, and its selective expression in inflammatory infiltrates suggests that it plays a role in the pathogenesis of inflammatory diseases. In this study, we used CD69-deficient (CD69 KO) mice to assess the role of CD69 in the pathogenesis of dextran sulphate sodium (DSS)-induced acute and chronic colitis. The severity of colitis was assessed by the survival rate, clinical signs, colon length, histological examination and the expression of cytokines and chemokines in the large intestines. Both acute and chronic colitis were attenuated in the CD69 KO mice, as reflected by the lower lethality, weight loss, clinical signs, and improved histological findings. CD69+ cells infiltrated extensively into the inflamed mucosa of the colon in WT mice after DSS treatment. Experiments with the transfer of WT CD4 T cells into CD69 KO mice restored the induction of colitis. The administration of an anti-CD69 antibody also inhibited the induction of the DSS-induced colitis. These results indicate that CD69 expressed on CD4 T cells plays an important role in the pathogenesis of DSS-induced acute and chronic colitis, and that CD69 could be a possible therapeutic target for colitis. [ABSTRACT FROM AUTHOR]

RNA interference (RNAi) mediated by siRNAs has proved to be a highly effective gene silencing mechanism with great potential for gene therapeutic applications. However, siRNA agents have been shown to exert non-target-related biological effects and toxicities, including immune stimulation. Specifically, siRNA synthesized from a T7 RNA polymerase system can trigger the potent induction of type I IFN in a variety of cells. The single-stranded RNA can also stimulate innate cytokine responses in mammals. We found that pppGn (n = 1-3), associated with the 5' end of the shRNA produced from the T7 RNA polymerase system, did not induce detectable levels of IFN. The residual amount of G associated with the 5'-end of the transcript was proportional to the reduction of the interferon response. We describe a T7 pppGn (n = 1-3) shRNA synthesis system that alleviates the IFN response, which will facilitate the design of siRNAs while maintaining their full efficacy. [ABSTRACT FROM AUTHOR]

Transgenic (TG) mice with TCR α and β chain genes from a CD4-dependent auto-l-A reactive T cell clone were generated. H-2 TG mice had a large number of thymic and splenic CD4 T cells expressing the autoreactive TCR without manifestation of autolmmunlty. The cells were not anergic, as they could respond to autologous antigen presenting cells and antl-TCR antibodies to proliferate and to produce interleuklns. Various degrees of down-regulation of CD2 and CD44 was observed in TG mice, Indicating the presence of a defective co-stlmulatory process in TG T cells. These features indicate that the self tolerance in autoreactive TCR TG mice is due not to clonal deletion and anergy but to a novel mechanism where T cells cannot sufficiently respond to normally existing self ligand . That such an in vivo unresponsiveness of autoreactive T cells is dictated in the thymus during CD4 T cell differentiation as an atypical form of positive selection of autoreactive T cells was suggested by the abnormal surface expression of CD69 and HSA. [ABSTRACT FROM PUBLISHER]