Chiori Shimizu

Regulation of Th2 cell differentiation by mel-18, a mammalian polycomb group gene.

Polycomb group (PcG) gene products regulate homeobox gene expression in Drosophila and vertebrates and also cell cycle progression of immature lymphocytes. In a gene-disrupted mouse for polycomb group gene mel-18, mature peripheral T cells exhibited normal anti-TCR-induced proliferation; however, the production of Th2 cytokines (IL-4, IL-5, and IL-13) was significantly reduced, whereas production of IFNgamma was modestly enhanced. Th2 cell differentiation was impaired, and the defect was associated with decreased levels in demethylation of the IL-4 gene. Significantly, reduced GATA3 induction was demonstrated. In vivo antigen-induced IgG1 production and Nippostrongylus brasiliensis-induced eosinophilia were significantly affected, reflecting the deficit in Th2 cell differentiation. Thus, the PcG gene products play a critical role in the control of Th2 cell differentiation and Th2-dependent immune responses.

src homology 2 domain–containing tyrosine phosphatase SHP-1 controls the development of allergic airway inflammation

Th2 cells are generated from naive CD4 T cells upon T cell receptor (TCR) recognition of antigen and IL-4 stimulation and play crucial roles in humoral immunity against infectious microorganisms and the pathogenesis of allergic and autoimmune diseases. A tyrosine phosphatase, SHP-1, that contains src homology 2 (SH2) domains is recognized as a negative regulator for various intracellular signaling molecules, including those downstream of the TCR and the IL-4 receptor. Here we assessed the role of SHP-1 in Th1/Th2 cell differentiation and in the development of Th2-dependent allergic airway inflammation by using a natural SHP-1 mutant, the motheaten mouse. CD4 T cells appear to develop normally in the heterozygous motheaten (me/+) thymus even though they express decreased amounts of SHP-1 (about one-third the level of wild-type thymus). The me/+ naive splenic CD4 T cells showed enhanced activation by IL-4 receptor-mediated signaling but only marginal enhancement of TCR-mediated signaling. Interestingly, the generation of Th2 cells was increased and specific cytokine production of mast cells was enhanced in me/+ mice. In an OVA-induced allergic airway inflammation model, eosinophilic inflammation, mucus hyperproduction, and airway hyperresponsiveness were enhanced in me/+ mice. Thus, SHP-1 may have a role as a negative regulator in the development of allergic responses, such as allergic asthma.

Inhibition of tumor metastasis by adoptive transfer of IL‐12‐activated Vα14 NKT cells

A unique lymphocyte lineage, the Vα14 NKT cells, expresses both NK1.1 and an invariant antigen receptor encoded by Vα14 and Jα281 gene segments. Vα14 NKT cells play crucial roles in various immune responses, including autoimmune diseases, allergic reactions and anti‐tumor immunity. Vα14 NKT cells were demonstrated to be essential for anti‐tumor effect of IL‐12 in vivo. Here, we report that adoptive transfer of IL‐12‐activated Vα14 NKT cells prevents hepatic metastasis of B16 melanoma. The injection of large amounts of IL‐2, IL‐4, and IFN‐γ, which are cytokines produced by activated Vα14 NKT cells, exhibited no significant inhibition of the metastasis of this melanoma. The cells prepared from the liver of IL‐12‐injected mice expressed a potent cytotoxic activity on B16 melanoma cells in vitro. Although the adoptive transfer of IL‐12‐activated Vα14 NKT cells prevents hepatic metastasis of B16 melanoma, activated NK cells from IL‐12‐injected RAG‐1−/− mice failed to inhibit the metastasis of this melanoma. Thus, the anti‐tumor effect of IL‐12 can be replaced by adoptive transfer of IL‐12‐activated Vα14 NKT cells but not by IL‐12‐activated NK cells, suggesting a minor role of NK cells for the IL‐12‐mediated anti‐tumor effect in this experimental system. Moreover, our studies have suggested the involvement of direct cytotoxic mechanisms rather than cytokine‐mediated immune responses at the effector phase of the Vα14 NKT cell‐mediated anti‐tumor activity.

Artificial lymph nodes induce potent secondary immune responses in naive and immunodeficient mice

We previously demonstrated that artificial lymph nodes (aLNs) could be generated in mice by the implantation of stromal cell-embedded biocompatible scaffolds into their renal subcapsular spaces. T and B cell domains that form in aLNs have immune response functions similar to those of follicles of normal lymphoid tissue. In the present study, we show that the aLNs were transplantable to normal as well as SCID mice, where they efficiently induced secondary immune responses. Antigen-specific secondary responses were strongly induced in aLNs even 4 weeks after their transplantation. The antigen-specific antibody responses in lymphocyte-deficient SCID mice receiving transplanted aLNs were substantial. The cells from the aLNs migrated to the SCID mouse spleen and BM, where they expanded to generate large numbers of antigen-specific antibody-forming cells. Secondary responses were maintained over time after immunization (i.e., antigen challenge), indicating that aLNs can support the development of memory B cells and long-lived plasma cells. Memory CD4(+) T cells were enriched in the aLNs and spleens of aLN-transplanted SCID mice. Our results indicate that aLNs support strong antigen-specific secondary antibody responses in immunodeficient mice and suggest the possibility of future clinical applications.

Gene organization of the quail major histocompatibility complex (MhcCoja) class I gene region

Abstract Class I genomic clones of the quail (Coturnix japonica) major histocompatibility complex (MhcCoja) were isolated and characterized. Two clusters spanning the 90.8 kilobase (kb) and 78.2 kb class I gene regions were defined by overlapping cosmid clones and found to contain at least twelve class I loci. However, unlike in the chicken Mhc, no evidence for the existence of any Coja class II gene was obtained in these two clusters. Based on comparative analysis of the genomic sequences with those of the cDNA clones, Coja-A, Coja-B, Coja-C, and Coja-D (Shiina et al. 1999), these twelve loci were assigned to represent one Coja-A gene, two Coja-B genes (Coja-B1 and -B2), four Coja-C genes (Coja-C1-C4), four Coja-D genes (Coja-D1-D4), and one new Coja-E gene. A class I gene-rich segment of 24.6 kb in which five of these genes (Coja-B1, -B2, -D1, -D2 and -E) are densely packed were sequenced by the shotgun strategy. All of these five class I genes are very compact in size [2089 base pairs (bp)–2732 bp] and contain no apparent genetic defect for functional expression. A transporter associated with the antigen processing (TAP) gene was identified in this class I gene-rich segment. These results suggest that the quail class I region is physically separated from the class II region and characterized by a large number of the expressible class I loci (at least seven) in contrast to the chicken Mhc, where the class I and class II regions are not clearly differentiated and only at most three expressed class I loci so far have been recognized.

Impaired GATA3-Dependent Chromatin Remodeling and Th2 Cell Differentiation Leading to Attenuated Allergic Airway Inflammation in Aging Mice

Age-related changes in lymphocytes are most prominent in the T cell compartment. There have been substantial numbers of reports on T cell function in aged mice and humans, such as on the production of Th1 and Th2 cytokines, but the results show considerable variation and contradictions. In the present study, we used 8- to 12-mo-old aging mice and a well-established in vitro Th1/Th2 cell differentiation culture system to identify molecular defects in Th1/Th2 cell differentiation that can be detected in the relatively early stages of aging. The capability to differentiate into Th2 cells is reduced in aging mouse CD4+ T cells. Decreased activation of the ERK MAPK cascade upon TCR stimulation, but normal intracellular-free calcium ion concentration mobilization and normal IL-4-induced STAT6 activation were observed in aging mouse CD4+ T cells. In addition, reduced expression of GATA3 was detected in developing Th2 cells. Chromatin remodeling of the Th2 cytokine gene locus was found to be impaired. Th2-dependent allergic airway inflammation was milder in aging mice compared with in young adult mice. These results suggest that the levels of Th2 cell differentiation and resulting Th2-dependent immune responses, including allergic airway inflammation, decline during aging through defects in the activation of the ERK MAPK cascade, expression of GATA3 protein and GATA3-dependent chromatin remodeling of the Th2 cytokine gene locus. In the present study, we provide the first evidence indicating that a chromatin-remodeling event in T cells is impaired by aging.

The Role of α-Galactosylceramide-Activated Vα14 Natural Killer T Cells in the Regulation of Th2 Cell Differentiation

Vα14 natural killer T (NKT) cells produce large amounts of both IL-4 and IFN-γ upon stimulation with a ligand, α-galactosylceramide (α-GalCer), and play a crucial role in various immune responses, including allergic diseases. Interestingly, Vα14 NKT cells are not essential for the induction of IgE responses but rather induce suppression of specific IgE production upon activation. The suppression in the IgE production is not detected either in Vα14 NKT cell-deficient mice or in IFN-γ-deficient mice. Thus, activated Vα14 NKT cells are likely to exert a potent suppressive activity on Th2 cell differentiation and subsequent IgE production by producing a large amount of IFN-γ. In marked contrast, little regulatory effect of IL-4 produced by Vα14 NKT cells on Th2 cell differentiation is suggested.

CD4 regulates the efficiency of an endogenous superantigen-induced clonal deletion of TCRV beta 11+ cells in the periphery.

Peripheral T‐cell antigen receptor Vβ (TCRVβ) repertoire is influenced by clonal deletion both in the thymus and periphery. Developing thymocytes expressing certain TCRVβ are deleted by endogenous superantigens presented on major histocompatibility complex (MHC) molecules in the thymus. Likewise, mature T cells bearing particular TCRVβ chains can be clonally deleted by superantigens in the periphery. The efficiency with which T cells expressing particular Vβ subunits are deleted differs depending upon which coreceptor is expressed. Indeed, while deletion of Vβ11+ splenic T cells in CBA/J (Mls‐1,a I‐E,+ MTV 9+) mice is quite efficient for CD4+ spleen T cells, it is much less efficient for CD8+ splenic T cells. If the difference in the efficiency of deletion is due solely to the coreceptor expressed, then a transgene encoding CD4 should increase the efficiency with which CD8+ cells are deleted. To address this question, we have produced CD4 transgenic (TG) mice that express physiologic levels of CD4 on all thymocytes and peripheral CD8 T cells. CD4 molecules expressed on CD8+ splenic T cells were associated with p56lck tyrosine kinase, and were functional as evidenced by their ability to facilitate class II alloreactivity. Furthermore, we found that ectopic expression of TG CD4 molecules on CD8+ T cells was able to affect the efficiency of deletion in response to superantigen stimulation. In particular, deletion of TCRVβ11+ T cells was much less efficient for CD8+ than for CD4+ T‐cell subpopulations in (CBA/J×B6) F1 mice. However, expression of the CD4 transgene on CD8+ splenic T cells from these mice increased the efficiency of deletion in the CD8+ Vβ11 T cells. Interestingly, this effect was not observed in a mature CD8+ thymocyte subpopulation. The results in this report demonstrate that CD4 molecules are involved in peripheral deletion of TCRVβ11+ T cells in (CBA/J×B6) F1 mice, and that the TCRVβ repertoire can be altered by ectopic expression of CD4 on all T‐lineage cells.