Regulatory T cells (T(reg) cells) develop from progenitor thymocytes after the engagement of T cell antigen receptors (TCRs) with high-affinity ligands, but the underlying molecular mechanisms are still unclear. Here we show that the Nr4a nuclear receptors, which are encoded by immediate-early genes upregulated by TCR stimulation in thymocytes, have essential roles in T(reg) cell development. Mice that lacked all Nr4a factors could not produce T(reg) cells and died early owing to systemic autoimmunity. Nr4a receptors directly activated the promoter of the gene encoding the transcription factor Foxp3, and forced activation of Nr4a receptors bypassed low-strength TCR signaling to drive the T(reg) cell developmental program. Our results suggest that Nr4a receptors have key roles in determining CD4(+) T cell fates in the thymus and thus contribute to immune homeostasis.

Plasmacytoid dendritic cells (pDCs) are characterized as type I interferon-producing cells that engage endosomal toll-like receptors (TLRs) and exclusively express sialic acid binding Ig-like lectin (Siglec)-H. However, their role in vivo remains unclear. Here we report a critical role for pDCs in the regulation of inflammation and T cell immunity in vivo by using gene-targeted mice with a deficiency of Siglec-H and conditional ablation of pDCs. pDCs were required for inflammation triggered by a TLR ligand as well as by bacterial and viral infections. pDCs controlled homeostasis of effector and regulatory CD4(+) T cells. Upon antigenic stimulation and microbial infection, pDCs suppressed the induction of CD4(+) T cell responses and participated in the initiation of CD8(+) T cell responses. Furthermore, Siglec-H appeared to modulate the function of pDCs in vivo. Thus, our findings highlight previously unidentified roles of pDCs and the regulation of their function for the control of innate and adaptive immunity.

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In order to characterize immunohistochemically the possible in-situ effects of gonadal steroid hormones in the human ovary during the menstrual cycle, we immunolocalized progesterone (PR), androgen (AR) and oestrogen (ER) receptors in 50 normal cycling human ovaries, and examined the relationship between these findings and the cellular localization of steroidogenic enzymes including cytochrome P-450 cholesterol side-chain cleavage (P-450scc) enzyme, 3 beta-hydroxysteroid dehydrogenase (3 beta HSD), cytochrome P-450 17 alpha-hydroxylase (P-450c17) and cytochrome P-450 aromatase (P-450arom). A large number of stromal cells were positive for AR, regardless of the distance from a follicle. No steroidogenic enzymes were observed in the stromal cells. In the pre-antral follicle, AR was observed in the theca cells. P-450scc, 3 beta HSD and P-450c17 were sporadically expressed in the theca cells in relatively large-sized pre-antral follicles. ER was positive in the granulosa cells only in the P-450arom-positive antral or pre-ovulatory follicle, which is likely to be a selected follicle. In the corpus luteum, in the period from ovulation to the mid-secretory phase, PR immunoreactivity was observed in a large number of both the luteinized granulosa and the theca cells. All steroidogenic enzymes were observed in all corpora lutea, but ER was negative in any corpus luteum. In the atretic follicle, AR was present in the theca interna cells. P-450scc, 3 beta HSD and P-450c17 were observed in the theca interna cells in some atretic follicles.(ABSTRACT TRUNCATED AT 250 WORDS)

In order to study alterations of angiogenesis and blood vessel regression through ovarian cycle in human ovaries we quantitatively examined vascularity in various stages in 24 normal human ovaries. Vascular density (VD; vessel numbers/10(-7) m2) and endothelial area of each vessel (EA; 10(-12) m2/vessel) were evaluated using immunohistochemistry of CD34 and CAS 200 image analysis system. Small-sized vessels were sporadically observed in stroma adjacent to primordial or primary follicles (6.73 +/- 1.83 for VD and 113.58 +/- 21.80 for EA). Formation of capillary network was observed in the theca layer of preantral follicles (PA; 15.28 +/- 2.77 for VD and 113.58 +/- 21.80 for EA), and higher density of the capillary network was detected in non-dominant follicles in follicular phase (ND-F) and dominant follicles (DF; 29.33 +/- 3.84 for VD and 179.69 +/- 41.25 for EA). Dense capillary network was still present in non-dominant follicles in luteal phase (ND-L) and atretic follicles (AF; 26.88 +/- 3.36 for VD and 110.88 +/- 50.53 for EA). After ovulation, developing capillaries were also observed in the luteinized granulosa layers in early corpus luteum (21.95 +/- 2.06 for VD and 167.08 +/- 29.59 for EA). Vessel density markedly increased in mid corpus luteum, reached plateau in late corpus luteum (60.85 +/- 5.92 for VD and 70.99 +/- 15.57 for EA) and remained constant during degenerating corpora lutea. Vascular endothelial growth factor was immunohistochemically observed in the theca cells in PA, ND-F, DF and ND-L in follicular stages, and functioning corpora lutea. Immunoreactivity of intercellular adhesion molecule-1 was detected only in post-capillary venules in early degenerating corpora lutea. These findings suggest that ovarian angiogenesis is a requirement for the early stages of folliculogenesis and luteal growth, and also plays an important role in the process of follicular atresia and luteal regression.

IL-9 is a pleiotropic cytokine that can regulate autoimmune and allergic responses. Th9 cells can develop from naive T cells or Th2 cells through stimulation by TGF-β in vitro. In this study, we demonstrated that Smad2 and Smad3 are necessary for IL-9 production from T cells in an OVA-induced asthma model using T cell–specific Smad2- and Smad3-deficient mice. Smad2 and Smad3 were also redundantly essential for TGF-β signaling to induce histone modifications for Il9 transcription. Although Smad2/3 was recruited to the Il9 promoter by TGF-β stimulation, they are not sufficient to activate the Il9 promoter. By the screening the transcription factors, we found that IFN regulatory factor 4 (IRF4) was essential for the Smad2/3-mediated Il9 promoter activation. In addition, Smad2/3 physically interacted with IRF4, and Smad2/3 did not bind to the Il9 promoter and could not induce Th9 in IRF4-deficient T cells. Similarly, IRF4 could not stimulate Il9 transcription in the absence of Smad2/3, and TGF-β enhanced IRF4 recruitment to the Il9 promoter in a Smad2/3-dependent manner. We propose that Smad2/3 and IRF4 cooperatively transactivate the Il9 promoter and play an important role in regulating allergic immune responses by inducing Th9 cells.

Human endometrial regeneration has been considered to be modulated by several growth factors. However, little is known about the detailed mechanisms involved in the repair of the endometrium during the menstrual period. Hepatocyte growth factor (HGF) is a pleiotropic growth factor that reportedly acts on various epithelial cells. In the present study, we observed HGF and mRNA expression in human endometrium and mRNA expression in cultured endometrial epithelial cells of the c-met gene by reverse transcription-polymerase chain reaction and Southern blot hybridization. We also examined the biological role of HGF on the regeneration of the endometrium by using cultured endometrial epithelial cells in their proliferative phase. With the proliferation assay, the addition of 10-50 ng/ml of HGF showed that HGF was mitogenic in a dose-dependent manner. With Boyden's chamber technique, 50 ng/ml of HGF significantly stimulated cell migration. In a three-dimensional cell-culture system, the endometrial epithelial cells formed cell clusters and gradually formed epithelial lumens, both of which were stimulated by 50 ng/ml of HGF. Results suggest the HGF stimulates the proliferation and migration of, and morphogenic changes in, endometrial epithelial cells. HGF may modulate the regeneration of the endometrium during menstruation.

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