The effect of proteasome inhibitor MG132 on experimental inflammatory bowel disease

Immunoproteasome up-regulation enhances the processing of nuclear factor-κB (NF-κB) and degradation of IκBα, which correlates with increased amounts of NF-κB in the various cells. Aberrant activation of NF-κB is involved in the pathogenesis of inflammatory bowel disease (IBD). The aim of this study was to elucidate the effect of proteasome inhibitor MG132 on experimental IBD. We investigated the effects of MG132 on intestinal inflammation and epithelial regeneration in both interleukin-10-deficient (IL-10^−/−) mice and mice with dextran sulphate sodium (DSS)-induced colitis. Body weight, histological findings and tumour necrosis factor (TNF)-α mRNA expression, epithelial cell proliferation and NF-κB p65 activity in colonic tissues were examined. The effects of MG132 on cell proliferation, migration and multiple drug resistance 1 (MDR1) gene expression were determined in vitro. MG132 ameliorated intestinal inflammation of IL-10^−/− mice by decreasing TNF-α mRNA expression in the colonic tissues, which was associated with suppression of NF-κB activation, and reduced significantly the number of Ki-67-positive intestinal epithelial cells. On the other hand, MG132 did not reduce intestinal inflammation in mice with DSS-induced colitis, and delayed significantly the recovery of body weight and epithelial regeneration. MG132 also suppressed significantly epithelial cell proliferation, cell migration and MDR1 gene expression in vitro. Proteasome inhibition reduces T cell-mediated intestinal inflammation, but may interrupt both epithelial regeneration and barrier function of colonic mucosa. Optimal use of proteasome inhibitor should be kept in mind when we consider its clinical application for patients with IBD.     

Distinct granuloma responses in C57BL/6J and BALB/cByJ mice in response to pristane

Granuloma formation is an inflammatory response of the host against invading pathogens or indigestible substances. We generated mesenteric oil granulomas by injecting pristane into the peritoneal cavity (PC) of mice, and compared oil granuloma formation in the C57BL/6J and BALB/cByJ strains of mice. The formation and kinetics of oil granulomas were distinct between the two strains. In C57BL/6J mice, injected pristane induced oil granuloma formation at both the mesenteric centers (MG) and margins (SG). MG was resolving by 11 weeks, and SG persisted. In BALB/cByJ mice, MG developed slower but persisted longer than in C57BL/6J mice, and SG resolved sooner than in C57BL/6J mice. Injection of India ink revealed that phagocytes were localised mainly to the SG in C57BL/6J mice, but were located diffusely in both MG and SG of BALB/cByJ mice. SG cells expressed more monocyte chemotactic protein‐1 (MCP‐1) mRNA than MG cells in C57BL/6J mice, but there was no difference in MCP‐1 expression between the MG and SG in BALB/cByJ mice. These observations suggest that the recruitment of inflammatory leucocytes under the direction of chemokines differentiates the patterns of granuloma responses to pristane in C57BL/6J and BALB/cByJ mice.     

Endogenous interleukin (IL)‐17A promotes pristane‐induced systemic autoimmunity and lupus nephritis induced by pristane

Interleukin (IL)-17A is increased both in serum and in kidney biopsies from patients with lupus nephritis, but direct evidence of pathogenicity is less well established. Administration of pristane to genetically intact mice results in the production of autoantibodies and proliferative glomerulonephritis, resembling human lupus nephritis. These studies sought to define the role of IL-17A in experimental lupus induced by pristane administration. Pristane was administered to wild-type (WT) and IL-17A^−/− mice. Local and systemic immune responses were assessed after 6 days and 8 weeks, and autoimmunity, glomerular inflammation and renal injury were measured at 7 months. IL-17A production increased significantly 6 days after pristane injection, with innate immune cells, neutrophils (Ly6G⁺) and macrophages (F4/80⁺) being the predominant source of IL-17A. After 8 weeks, while systemic IL-17A was still readily detected in WT mice, the levels of proinflammatory cytokines, interferon (IFN)-γ and tumour necrosis factor (TNF) were diminished in the absence of endogenous IL-17A. Seven months after pristane treatment humoral autoimmunity was diminished in the absence of IL-17A, with decreased levels of immunoglobulin (Ig)G and anti-dsDNA antibodies. Renal inflammation and injury was less in the absence of IL-17A. Compared to WT mice, glomerular IgG, complement deposition, glomerular CD4⁺ T cells and intrarenal expression of T helper type 1 (Th1)-associated proinflammatory mediators were decreased in IL-17A^−/− mice. WT mice developed progressive proteinuria, but functional and histological renal injury was attenuated in the absence of IL-17A. Therefore, IL-17A is required for the full development of autoimmunity and lupus nephritis in experimental SLE, and early in the development of autoimmunity, innate immune cells produce IL-17A.     

Mice genetically inactivated in interleukin‐17A receptor are defective in long‐term control of Mycobacterium tuberculosis infection

Interleukin-17A (IL-17A), a pro-inflammatory cytokine acting on neutrophil recruitment, is known to play an important role during Mycobacterium tuberculosis infection, but the role of IL-17A receptor signalling in immune defence against this intracellular pathogen remains poorly documented. Here we have analysed this signalling using C57BL/6 mice genetically inactivated in the IL-17 receptor A subunit (IL-17RA^−/−). Although early after infection bacterial growth was controlled to the same extent as in wild-type mice, IL-17RA^−/− mice were defective in exerting long-term control of M. tuberculosis infection, as demonstrated by a progressively increasing pulmonary bacterial burden and shortened survival time. Compared with infected wild-type mice, IL-17RA^−/− mice showed impaired recruitment of neutrophils to the lungs at the early but not the late stage of infection. Pulmonary tumour necrosis factor-α, IL-6 and particularly IL-10 levels were decreased in the absence of IL-17RA signalling, whereas IL-1β was increased. CD4⁺-mediated and γδ-mediated IL-17A production was dramatically increased in IL-17RA^−/− mice (confirming part of their phenotype), whereas production of interferon-γ and expression of the bactericidal enzyme inducible nitric oxide synthase were not affected. Collectively, our data suggest that early but not late neutrophil recruitment is essential for IL-17A-mediated long-term control of M. tuberculosis infection and that a functional interferon-γ response is not sufficient to control M. tuberculosis growth when the IL-17RA pathway is deficient. As treatment of auto-immune diseases with anti-IL-17A antibodies is actually being tested in clinical studies, our data suggest that caution should be taken with respect to possible reactivation of tuberculosis.     

Toll-like receptor 4-mediated signaling regulates IL-7-driven proliferation and differentiation of B-cell precursors

Lipopolysaccharide （LPS） is known to be a potent activator of mature B cells by signaling through Toll-like receptor 4 （TLR4）. Its impact on early B-cell development, however, is not well defined. When comparing to C3H/HeN mice, TLR4-mutant C3H/HeJ mice showed an increase in the number of pro-B and pre-B cells in the bone marrow. When cultured in the presence of IL-7, the proliferation of pro-B and large pre-B cells was significantly inhibited by LPS, possibly due to reduced IL-7 receptor-a （IL-7Ra） expression. Meanwhile, the generation of IgM＋/IgD＋ B cells was greatly enhanced in IL-7 cultures of pro-B and pre-B cells. Consistent with these results, treatment with LPS facilitated the progression of adoptively transferred B220＋IgM-IgD- precursors into IgD＋ cells. Overall, these data suggest that LPS has a profound influence on early B-cell development, which may contribute to the deregulated B-cell development under physiological and pathological conditions such as bacterial infections.     

Enhanced differentiation of intraepithelial lymphocytes in the intestine of polymeric immunoglobulin receptor‐deficient mice

To clarify the effect of secretory IgA (sIgA) deficiency on gut homeostasis, we examined intraepithelial lymphocytes (IELs) in the small intestine (SI) of polymeric immunoglobulin receptor-deficient (pIgR^−/−) mice. The pIgR^−/− mice exhibited the accumulation of CD8αβ⁺ T-cell receptor (TCR)-αβ⁺ IELs (CD8αβ⁺αβ-IELs) after weaning, but no increase of CD8αβ⁺γδ-IELs was detected in pIgR^−/− TCR-β^−/− mice compared with pIgR^+/+ TCR-β^−/− mice. When 5-bromo-2′-deoxyuridine (BrdU) was given for 14 days, the proportion of BrdU-labelled cells in SI-IELs was not different between pIgR^+/+ mice and pIgR^−/− mice. However, the proportion of BrdU-labelled CD8αβ⁺-IELs became higher in pIgR^−/− mice than pIgR^+/+ mice 10 days after discontinuing BrdU-labelling. Intravenously transferred splenic T cells migrated into the intraepithelial compartments of pIgR^+/+ TCR-β^−/− mice and pIgR^−/− TCR-β^−/− mice to a similar extent. In contrast, in the case of injection of immature bone marrow cells, CD8αβ⁺αβ-IELs increased much more in the SI of pIgR^−/− TCR-β^−/− mice than pIgR^+/+ TCR-β^−/− mice 8 weeks after the transfer. αβ-IELs from pIgR^−/− mice could produce more interferon-γ and interleukin-17 than those of pIgR^+/+ mice, and intestinal permeability tended to increase in the SI of pIgR^−/− mice with aging. Taken together, these results indicate that activated CD8αβ⁺αβ-IELs preferentially accumulate in pIgR^−/− mice through the enhanced differentiation of immature haematopoietic precursor cells, which may subsequently result in the disruption of epithelial integrity.     

Regulation of inflammasome activity

Granulomatous experimental autoimmune thyroiditis (G-EAT) is induced by mouse thyroglobulin (MTg)-sensitized splenocytes activated with MTg and interleukin (IL)-12. Our previous studies showed that, when used as donors and recipients, interferon (IFN)-γ^−/− and wild-type (WT) DBA/1 mice both develop severe G-EAT. Thyroid lesions in IFN-γ^−/− mice have many eosinophils and few neutrophils, while those in WT mice have extensive neutrophil infiltration and few eosinophils. Thyroid lesions in IFN-γ^−/− mice consistently resolve by day 40–50, whereas those in WT mice have ongoing inflammation and fibrosis persisting for more than 60 days. To determine if the extensive infiltration of eosinophils in thyroids of IFN-γ^−/− mice contributes to thyroid damage and/or early resolution of G-EAT, anti-IL-5 was used to inhibit migration of eosinophils to thyroids. G-EAT severity was compared at day 20 and day 40–50 in IFN-γ^−/− recipients given anti-IL-5 or control immunoglobulin G (IgG). Thyroids of anti-IL-5-treated IFN-γ^−/− mice had few eosinophils and more neutrophils at day 20, but G-EAT severity scores were comparable to those of control IgG-treated mice at both day 20 and day 40–50. Expression of chemokine (C-X-C motif) ligand 1 (CXCL1) mRNA was higher and that of chemokine (C-C motif) ligand 11 (CCL11) mRNA was lower in thyroids of anti-IL-5-treated IFN-γ^−/− mice. IL-5 neutralization did not influence mRNA expression of most cytokines in IFN-γ^−/− mice. Thus, inhibiting eosinophil migration to thyroids did not affect G-EAT severity or resolution in IFN-γ^−/− mice, suggesting that eosinophil infiltration of thyroids occurs as a consequence of IFN-γ deficiency, but these cells have no apparent pathogenic role in G-EAT.     

I L- 15 trans-presentation regulates homeostasis of CD4^＋ T lymphocytes

Interleukin-15 （IL-15） is essential for the survival of memory CD8^＋ and CD4^＋ T cell subsets, and natural killer and natural killer T cells. Here, we describe a hitherto unreported role of IL-15 in regulating homoeostasis of naive CD4^＋ T cells. Adoptive transfer of splenocytes from non-obese diabetic （NOD） mice results in increased homeostatic expansion of T cells in lymphopenic NOD.scid.II15^-/- mice when compared to NOD.scid recipients. The increased accumulation of CD4^＋ T cells is also observed in NOD.II15^-/- mice, indicating that IL-15-dependent regulation also occurs in the absence of lymphopenia. NOD.scid mice lacking the I L- 15Ra chain, but not those lacking the common gamma chain, also show increased accumulation of CD4^＋ T cells. These findings indicate that the IL-15-mediated regulation occurs directly on CD4^＋ T cells and requires trans-presentation of IL-15. CD4^＋ T cells expanding in the absence of IL-15 signaling do not acquire the characteristics of classical regulatory T cells. Rather, CD4^＋ T cells expanding in the absence of IL-15 show impaired antigen-induced activation and IFN-7 production. Based on these findings, we propose that the IL-15-dependent regulation of the naive CD4^＋ T-cell compartment may represent an additional layer of control to thwart potentially autoreactive cells that escape central tolerance, while permitting the expansion of memory T cells.     

CXCR3 deficiency enhances tumor progression by promoting macrophage M2 polarization in a murine breast cancer model

Tumor associated macrophages play a vital role in determining the outcome of breast cancer. We investigated the contribution of the chemokine receptor CXCR3 to antitumor immune responses using a cxcr3 deficient mouse orthotopically injected with a PyMT breast cancer cell line. We observed that cxcr3 deficient mice displayed increased IL-4 production and M2 polarization in the tumors and spleens compared to WT mice injected with PyMT cells. This was accompanied by larger tumor development in cxcr3^−/− than in WT mice. Further, tumor-promoting myeloid derived immune cell populations accumulated in higher proportions in the spleens of cxcr3 deficient mice. Interestingly, cxcr3^−/− macrophages displayed a deficiency in up-regulating inducible nitric oxide synthase after stimulation by either IFN-γ or PyMT supernatants. Stimulation of bone marrow derived macrophages by PyMT supernatants also resulted in greater induction of arginase-1 in cxcr3^−/− than WT mice. Further, cxcr3^−/− T cells activated with CD3/CD28 in vitro produced greater amounts of IL-4 and IL-10 than T cells from WT mice. Our data suggests that a greater predisposition of cxcr3 deficient macrophages towards M2 polarization contributes to an enhanced tumor promoting environment in cxcr3 deficient mice. Although CXCR3 is known to be expressed on some macrophages, this is the first report that demonstrates a role for CXCR3 in macrophage polarization and subsequent breast tumor outcomes. Targeting CXCR3 could be a potential therapeutic approach in the management of breast cancer tumors.     

Interleukin-13 Receptor α1-Dependent Responses in the Intestine Are Critical to Parasite Clearance

Nematode infection upregulates interleukin-4 (IL-4) and IL-13 and induces STAT6-dependent changes in gut function that promote worm clearance. IL-4 and IL-13 activate the type 2 IL-4 receptor (IL-4R), which contains the IL-13Rα1 and IL-4Rα chains. We used mice deficient in IL-13Rα1 (IL-13Rα1^−/−) to examine the contribution of IL-13 acting at the type 2 IL-4R to immune and functional responses to primary (Hb1) and secondary (Hb2) infections with the gastrointestinal nematode parasite Heligmosomoides bakeri. There were differences between strains in the IL-4 and IL-13 expression responses to Hb1 but not Hb2 infection. Following Hb2 infection, deficient mice had impaired worm expulsion and higher worm fecundity despite normal production of Th2-derived cytokines. The upregulation of IL-25 and IL-13Rα2 in Hb1- and Hb2-infected wild-type (WT) mice was absent in IL-13Rα1^−/− mice. Goblet cell numbers and resistin-like molecule beta (RELM-β) expression were attenuated significantly in IL-13Rα1^−/− mice following Hb2 infections. IL-13Rα1 contributes to the development of alternatively activated macrophages, but the type 1 IL-4R is also important. Hb1 infection had no effects on smooth muscle function or epithelial permeability in either strain, while the enhanced mucosal permeability and changes in smooth muscle function and morphology observed in response to Hb2 infection in WT mice were absent in IL-13Rα1^−/− mice. Notably, the contribution of claudin-2, which has been linked to IL-13, does not mediate the increased mucosal permeability following Hb2 infection. These results show that activation of IL-13Rα1 is critical for key aspects of the immune and functional responses to Hb2 infection that facilitate expulsion.     

Dietary gluten alters the balance of pro‐inflammatory and anti‐inflammatory cytokines in T cells of BALB/c mice

Several studies have documented that dietary modifications influence the development of type 1 diabetes. However, little is known about the interplay of dietary components and the penetration of diabetes incidence. In this study we tested if wheat gluten is able to induce differences in the cytokine pattern of Foxp3⁺ regulatory T cells, as well as Foxp3⁻ T cells, isolated from intestinal mucosal lymphoid tissue and non-mucosal lymphoid compartments in BALB/c mice. The gluten-containing standard diet markedly changed the cytokine expression within Foxp3⁻ T cells, in all lymphoid organs tested, towards a higher expression of pro-inflammatory interferon-γ (IFN-γ), interleukin-17 (IL-17) and IL-2. In Foxp3⁺ regulatory T cells, gluten ingestion resulted in a mucosal increase in IL-17 and IL-2 and an overall increase in IFN-γ and IL-4. The gluten-free diet induced an anti-inflammatory cytokine profile with higher proportion of transforming growth factor-β (TGF-β)⁺ Foxp3⁻ T cells in all tested lymphoid tissues and higher IL-10 expression within non-T cells in spleen, and a tendency towards a mucosal increase in TGF-β⁺ Foxp3⁺ regulatory T cells. Our data shows that the gluten-containing standard diet modifies the cytokine pattern of both Foxp3⁻ T cells and Foxp3⁺ regulatory T cells towards a more inflammatory cytokine profile. This immune profile may contribute to the higher type 1 diabetes incidence associated with gluten intake.     

β-Arrestin-1 Deficiency Protects Mice from Experimental Colitis

β-Arrestins are intracellular scaffolding proteins that modulate specific cell signaling pathways. Recent studies, in both cell culture and in vivo models, have demonstrated an important role for β-arrestin-1 in inflammation. However, the role of β-arrestin-1 in the pathogenesis of inflammatory bowel disease (IBD) is not known. Our goal was to investigate the role of β-arrestin-1 in IBD using mouse models of colitis. To this end, we subjected wild-type (WT) and β-arrestin-1 knockout (β-arr-1^−/−) mice to colitis induced by trinitrobenzenesulfonic acid or dextran sulfate sodium and examined the clinical signs, gross pathology, and histopathology of the colon, as well as inflammatory components. The β-arr-1^−/− mice displayed significantly attenuated colitis, compared with WT mice, in both models. Consistent with the phenotypic observations, histological examination of the colon revealed attenuated disease pathology in the β-arr-1^−/− mice. Our results further demonstrate that β-arr-1^−/− mice are deficient in IL-6 expression in the colon, but have higher expression of the anti-inflammatory IL-10 family of cytokines. Our results also demonstrate diminished ERK and NFκB pathways in the colons of β-arr-1^−/− mice, compared with WT mice. Taken together, our results demonstrate that decreased IL-6 production and enhanced IL-10 and IL-22 production in β-arrestin-1–deficient mice likely lead to attenuated gut inflammation.Arrestins are scaffolding proteins now classified into α and β arrestin families.¹ The β-arrestins were discovered for their role in binding to phosphorylated G-protein coupled receptors (GPCRs) to evoke receptor desensitization. Of the four members of the β-arrestin family, β-arrestin-1 (originally arrestin-2) and β-arrestin-2 (originally arrestin-3) are ubiquitously distributed. Even though their role in receptor desensitization has been well characterized and has been shown to have pharmacological and therapeutic implications, recent studies indicate that β-arrestins have a much broader role in cell signaling related to both GPCRs and non-GPCRs.² In addition, although several members of the arrestin family are present during development, the crucial ones are β-arrestins 1 and 2, because deletion of both results in embryonic lethality.³ Several studies have shown that β-arrestins, by virtue of regulating cell signaling, are able to modulate a variety of cell biological processes including gene expression, chemotaxis, proliferation, and apoptosis. Although β-arrestin-1 and -2 have been shown to have many overlapping cellular functions, they also have unique roles of their own.²Because of their critical role in many cellular functions, β-arrestins are crucial in the pathogenesis of many different diseases, including Parkinson''s disease, multiple sclerosis, cardiovascular disease, rheumatoid arthritis, sepsis, and allergic asthma.^4–8 In this context, we recently showed that β-arrestin-1 and -2 have differential and overlapping roles in endotoxin- and adenovirus-induced inflammatory responses in vivo.^9,10 In addition, other researchers have also shown that β-arrestin-2 plays a crucial role in sepsis and arthritis models of inflammatory disease.^7,11 Although it is clear that β-arrestins are important modulators of inflammation, nonetheless the role of β-arrestins in gastrointestinal inflammation is not known.Inflammatory bowel disease (IBD) affects more than 1.4 million people in the United States and accounts for more than $1.7 billion dollars in health care costs.¹² IBD broadly includes both Crohn''s disease and ulcerative colitis, both of which are characterized by chronic relapsing inflammation of the gastrointestinal tract.¹³ Importantly, IBD requires lifetime care and currently has no medical cure. Understanding the mechanisms involved in the pathogenesis of IBD is crucial for developing new therapeutic strategies to prevent or cure this inflammatory disease. In this regard, recent studies have shown that activation of Toll-like receptors (TLRs) and production of inflammatory cytokines are important mediators in the pathogenesis of colitis, including in mouse models of chemically induced colitis.^14–17 Previous studies from our laboratory have demonstrated that β-arrestin-1 mediates TLR signaling and the consequent inflammatory cytokine production in vivo.⁹ Based on these data, we hypothesized that β-arrestin-1 is an important and critical regulator of colitis pathogenesis. Using two different colitis models, we demonstrate here that β-arrestin-1 is a crucial mediator of colitis pathogenesis in mice. Deficiency of β-arrestin-1 almost completely abrogated the development of intestinal inflammation in the dextran sulfate sodium (DSS) model of colitis, whereas inflammation was significantly attenuated in the trinitrobenzenesulfonic acid (TNBS) model. Furthermore, our results also demonstrate that lack of β-arrestin-1 leads to diminished production of IL-6 but enhanced production of cytokines IL-10 and IL-22, and in combination these likely result in a favorable outcome for intestinal inflammation. The present study implicates a β-arrestin-1–mediated signaling pathway as a potential molecular target in the treatment of colitis.     

Interleukin‐12 (IL‐12), but not IL‐23, induces the expression of IL‐7 in microglia and macrophages: implications for multiple sclerosis

Interleukin-12 (IL-12) p70 and IL-23 are bioactive cytokines and their biological functions are becoming clear. Increased expression of IL-7 in the central nervous system as well as in peripheral immune cells is associated with multiple sclerosis and experimental allergic encephalomyelitis. Here, we describe the induction of IL-7 in primary mouse and human microglia, BV-2 microglial cells, mouse peritoneal macrophages and astrocytes by IL-12p70. Interestingly, IL-12 strongly induced the expression of IL-7 whereas IL-23 and other p40 family members remained weak inducers of IL-7 in these cell types. Consistently, IL-12, but not IL-23 and other p40 family members, induced IL-7 promoter-driven luciferase activity in microglial cells. Among various stimuli tested, IL-12 emerged as the most potent stimulus followed by bacterial lipopolysaccharide and HIV-1 gp120 in inducing the activation of IL-7 promoter in microglial cells. Furthermore, increase in IL-7 mRNA expression by over-expression of IL-12p35 subunit, but not p40 and IL-23 p19 subunit, confirm that p35, but not p40 and p19, is responsible for the induction of IL-7. Finally, by using primary microglia from IL-12 receptor β1-deficient (IL-12Rβ1^−/−) and IL-12Rβ2^−/− mice, we demonstrate that IL-12 induces the expression of IL-7 in microglia and macrophages via both IL-12Rβ2 and IL-12Rβ1. These studies delineate a novel biological function of IL-12 that is absent in IL-23 and other p40 family members.     

Calcineurin deficiency decreases inflammatory lesions in transforming growth factor β1‐deficient mice

Transforming growth factor (TGF) β1) is an immunoregulatory cytokine involved in self-tolerance and lymphocyte homeostasis. Tgfb1 knock-out (KO) mice develop severe multi-focal autoimmune inflammatory lesions due to [Ca²⁺]i deregulation in T cells, and die within 3 weeks after birth. Because the calcineurin inhibitor FK506 inhibits the hyperresponsiveness of Tgfb1^−/− thymocytes, and because calcineurin Aβ (CNAβ)-deficient mice do not reject allogenic tumours, we have generated Tgfb1^−/−Cnab^−/− mice to address whether CNAβ deficiency prevents T cell activation and inflammation in Tgfb1^−/− mice. Here we show that in Tgfb1^−/−Cnab^−/− mice inflammation is reduced significantly relative to that in Tgfb1^−/− mice. However, both CD4⁺ and CD8⁺ T cells in double knock-out (DKO) mice are activated, as revealed by up-regulation of CD11a lymphocyte function-associated antigen-1 (LFA-1), CD44 and CD69 and down-regulation of CD62L. These data suggest that deficiency of CNAβ decreases inflammatory lesions but does not prevent activation of autoreactive T cells. Also Tgfb1^−/− T cells can undergo activation in the absence of CNAβ, probably by using the other isoform of calcineurin (CNAα) in a compensatory manner. CNAβ-deficient T cells undergo spontaneous activation in vivo and are activated upon anti-T cell receptor stimulation in vitro. Understanding the role of calcineurin in T cell regulation should open up new therapeutic opportunities for inflammation and cancer.     

Ly49 receptors activate angiogenic mouse DBA＋ uterine natural killer cells

In humans, specific patterns of killer immunoglobulin-like receptors （KIRs） expressed by uterine natural killer （uNK） cells are linked through HLA-C with pregnancy complications （infertility, recurrent spontaneous abortion, intrauterine growth restriction and preeclampsia）. To identify mechanisms underpinning the associations between NK cell activation and pregnancy success, pregnancies were studied in mice with genetic knockdown （KD） of the MHC-activated Ly49 receptor gene family. B6.Ly49KD pregnancies were compared to normal control B6.Ly49z29 and C57BL/6 （B6） pregnancies. At mid-pregnancy （gestation day （gd9.5））, overall uNK cell （TCRI~-CD122＋DBA＋DX5- （DBA＋DX5-）） and TCRIβ-CD122＋DBA-DX5＋ （DBA-DX5＋）） frequencies in pregnant uterus were similar between genotypes. Ly49KD lowered the normal frequencies of Ly49＋ uNK cells from 90.3% to 47.8% in DBA-DX5＋ and 78.8% to 6.3% in DBA＋DX5- uNK cell subtypes. B6.Ly49KD matings frequently resulted in expanded blastocysts that did not implant （subfertility）. B6.Ly49KD mice that established pregnancy had gestational lengths and litter sizes similar to controls. B6.Ly49KD neonates, however, were heavier than controls. B6.Ly49KD implantation sites lagged in early （gd6.5） decidual angiogenesis and were deficient in mid-pregnancy （gd 10.5） spiral arterial remodelling. Ultrastructural analyses revealed that B6.Ly49KD uNK cells had impaired granulogenesis, while immunocytochemistry revealed deficient vascular endothelial cell growth factor （VEGFA） production. Perforin and IFNG expression were normal in B6.Ly49KD uNK cells. Thus, in normal mouse pregnancies, Ly49 receptor signaling must promote implantation, early decidual angiogenesis and mid-pregnancy vascular remodelling. Disturbances in these functions may underlie the reported genetic associations between human pregnancy complications and the inability of specific conceptus MHCs to engage activating KIR on uNK cells.     

Gold‐ and silver‐induced murine autoimmunity – requirement for cytokines and CD28 in murine heavy metal‐induced autoimmunity

Treatment with gold in the form of aurothiomaleate, silver or mercury (Hg) in genetically susceptible mouse strains (H-2^s) induces a systemic autoimmune condition characterized by anti-nuclear antibodies targeting the 34-kDa nucleolar protein fibrillarin, as well as lymphoproliferation and systemic immune-complex (IC) deposits. In this study we have examined the effect of single-gene deletions for interferon (IFN)-γ, interleukin (IL)-4, IL-6 or CD28 in B10.S (H-2^s) mice on heavy metal-induced autoimmunity. Targeting of the genes for IFN-γ, IL-6 or CD28 abrogated the development of both anti-fibrillarin antibodies (AFA) and IC deposits using a modest dose of Hg (130 µg Hg/kg body weight/day). Deletion of IL-4 severely reduced the IgG1 AFA induced by all three metals, left the total IgG AFA response intact, but abrogated the Hg-induced systemic IC deposits. In conclusion, intact IFN-γ and CD28 genes are necessary for induction of AFA with all three metals and systemic IC deposits using Hg, while lack of IL-4 distinctly skews the metal-induced AFA response towards T helper type 1. In a previous study using a higher dose of Hg (415 µg Hg/kg body weight/day), IC deposits were preserved in IL-4^−/− and IL-6^−/− mice, and also AFA in the latter mice. Therefore, the attenuated autoimmunity following loss of IL-4 and IL-6 is dose-dependent, as higher doses of Hg are able to override the attenuation observed using lower doses.