Zhen-Wu-Tang ameliorates lupus nephritis by diminishing renal tissue-resident memory CD8+ T cells via suppressing IL-15/STAT3 pathway.

Zhen-Wu-Tang (ZWT), a conventional herbal mixture, has been recommended for treating lupus nephritis (LN) in clinic. However, its mechanisms of action remain unknown. Here we aimed to define the immunological mechanisms underlying the effects of ZWT on LN and to determine whether it affects renal tissue-resident memory T (TRM) cells. Murine LN was induced by a single injection of pristane, while in vitro TRM cells differentiated with IL-15/TGF-ß. We found that ZWT or mycophenolate mofetil treatment significantly ameliorated kidney injury in LN mice by decreasing 24-h urine protein, Scr and anti-dsDNA Ab. ZWT also improved renal pathology and decreased IgG and C3 depositions. In addition, ZWT down-regulated renal Desmin expression. Moreover, it lowered the numbers of CD8+ TRM cells in kidney of mice with LN while decreasing their expression of TNF-α and IFN-γ. Consistent with in vivo results, ZWT-containing serum inhibited TRM cell differentiation induced by IL-15/TGF-ß in vitro. Mechanistically, it suppressed phosphorylation of STAT3 and CD122 （IL2/IL-15Rß）expression in CD8+ TRM cells. Importantly, ZWT reduced the number of total F4/80+CD11b+ and CD86+, but not CD206+, macrophages in the kidney of LN mice. Interestingly, ZWT suppressed IL-15 protein expression in macrophages in vivo and in vitro. Thus, we have provided the first evidence that ZWT decoction can be used to improve the outcome of LN by reducing CD8+ TRM cells via inhibition of IL-15/IL-15R /STAT3 signaling.

[Screening of small molecule inhibitors of IL-15Rα using molecular docking and surface plasmon resonance technology].

The study aims to explore the active molecules of traditional Chinese medicine that specifically bind to interleukin-15 receptor α (IL-15Rα) using molecular docking and surface plasmon resonance (SPR) technology. AutoDock molecular docking software was used to perform simulated docking of more than 3 000 compounds from 48 traditional Chinese medicines at IL-15Rα and screen the specific binding compounds. Then Biocore T200 biomolecular interaction analysis system of SPR was used to confirm the binding specificity of the selected target compounds. Finally, the biological effects of the target compounds on IL-15Rα were verified by cell biological experiments. The results showed that neoprzewaquinone A (Neo) possessed the highest specific binding affinity among the active molecules from traditional Chinese medicine, and the dissociation constant (KD) value was (0.62 ± 0.20) µmol/L. The results of cell experiment showed that Neo significantly inhibited the proliferation of Mo7e cells induced by IL-15, and the IC50 was 1.075 µmol/L, approximately 1/120 of the IC50 of Cefazolin (IL-15 specific antagonist). These results suggest that Neo is a specific inhibitor of IL-15Rα and may be a potential active drug for the treatment of diseases related to the dysfunction of the IL-15Rα signaling.

Enhanced serum levels of tumor necrosis factor-α, interleukin-1ß, and -6 in sarcopenia: alleviation through exercise and nutrition intervention.

BACKGROUND: Limited research has been conducted on the post-intervention inflammatory status in sarcopenic patients, despite previous studies revealing elevated pro-inflammatory markers. This study aimed to investigate the potential elevation of specific pro-inflammatory cytokines in sarcopenic patients and evaluate the effects of exercise and nutritional support interventions on these cytokine levels. METHODS: In this post-hoc analysis of a randomized controlled trial (RCT), 57 individuals with sarcopenia from the RCT and 57 non-sarcopenic participants from the same geriatric community cohort that did not participate in the RCT were enrolled. Grip strength and body composition measurements were recorded. Tumor necrotizing factor (TNF)-α, interleukin (IL)-1ß, IL-6, and IL-15 levels were assessed at baseline for both groups and after a 12-week intervention consisting of resistive exercise and supplementation with branched-chain amino acids, calcium, and vitamin D3 in the patients with sarcopenia. RESULTS: The sarcopenic group demonstrated significantly lower body weight, body mass index, grip strength, and skeletal muscle mass index. Moreover, sarcopenic patients exhibited higher levels of TNF-α (p=0.007), IL-1ß (p<0.001), and IL-6 (p<0.001), while no significant difference was observed in IL-15 (p=0.345) between participants with and those without sarcopenia. Following the intervention, the sarcopenic group experienced significant improvements in grip strength and skeletal muscle mass index with a notable reduction in TNF-α (p=0.003), IL-1ß (p=0.012) and IL-6 (p=0.001) levels. CONCLUSIONS: Sarcopenic patients exhibit elevated levels of TNF-α, IL-1ß, and IL-6, which declined after nutrition support and exercise interventions. However, further research is necessary to evaluate the long-term impact of these interventions on cytokine levels.

IL-15 Prevents Renal Fibrosis by Inhibiting Collagen Synthesis: A New Pathway in Chronic Kidney Disease?

Chronic kidney disease (CKD), secondary to renal fibrogenesis, is a public health burden. The activation of interstitial myofibroblasts and excessive production of extracellular matrix (ECM) proteins are major events leading to end-stage kidney disease. Recently, interleukin-15 (IL-15) has been implicated in fibrosis protection in several organs, with little evidence in the kidney. Since endogenous IL-15 expression decreased in nephrectomized human allografts evolving toward fibrosis and kidneys in the unilateral ureteral obstruction (UUO) model, we explored IL-15's renoprotective role by pharmologically delivering IL-15 coupled or not with its soluble receptor IL-15Rα. Despite the lack of effects on myofibroblast accumulation, both IL-15 treatments prevented tubulointerstitial fibrosis (TIF) in UUO as characterized by reduced collagen and fibronectin deposition. Moreover, IL-15 treatments inhibited collagen and fibronectin secretion by transforming growth factor-ß (TGF-ß)-treated primary myofibroblast cultures, demonstrating that the antifibrotic effect of IL-15 in UUO acts, in part, through a direct inhibition of ECM synthesis by myofibroblasts. In addition, IL-15 treatments resulted in decreased expression of monocyte chemoattractant protein 1 (MCP-1) and subsequent macrophage infiltration in UUO. Taken together, our study highlights a major role of IL-15 on myofibroblasts and macrophages, two main effector cells in renal fibrosis, demonstrating that IL-15 may represent a new therapeutic option for CKD.

Environmental activation of a hypothalamic BDNF-adipocyte IL-15 axis regulates adipose-natural killer cells.

Physical and social environments influence immune homeostasis within adipose tissue, yet the mechanisms remain poorly defined. We report that an enriched environment (EE) housing modulates the immune cell population in white adipose tissue of mice including an increase in the abundance of natural killer (NK) cells. EE upregulates the expression of IL-15 and its receptor IL-15Rα specifically within mature adipocytes. Mechanistically, we show that hypothalamic brain-derived neurotrophic factor (BDNF) upregulates IL-15 production in adipocytes via sympathetic ß-adrenergic signaling. Overexpressing BDNF mediated by recombinant adeno-associated virus (rAAV) vector in the hypothalamus expands adipose NK cells. Conversely, inhibition of hypothalamic BDNF signaling via gene transfer of a dominant negative TrkB receptor suppresses adipose NK cells. In white adipose tissue, overexpression of IL-15 using an adipocyte-specific rAAV vector stimulates adipose NK cells and inhibits the progression of subcutaneous melanoma, whereas local IL-15 knockdown blocks the EE effect. These results suggest that bio-behavioral factors regulate adipose NK cells via a hypothalamic BDNF-sympathoneural-adipocyte IL-15 axis. Targeting this pathway may have therapeutic significance for cancer.

Dihydroartemisinin ameliorates psoriatic skin inflammation and its relapse by diminishing CD8+ T-cell memory in wild-type and humanized mice.

Conventional immunosuppressants cause side effects and do not prevent the recurrence of autoimmune diseases. Moreover, they may not inhibit autoimmunity mediated by pathogenic memory T-cells. Dihydroartemisinin (DHA) has been shown to regulate autoimmunity. However, it remains unknown whether DHA impacts psoriasis and its recurrence. The objective of this study was to determine therapeutic effects of DHA on psoriasis and its relapse as well as its underlying mechanisms. Methods: We established animal models of imiquimod (IMQ)-induced psoriasis-like wild-type mice and humanized NSG mice receiving lesional human skin from patients with psoriasis. Many immunoassays, including immunohistochemistry, flow cytometry, quantitative RT-PCR and Western blotting, were performed. Results: We found that DHA not only ameliorated acute skin lesion of psoriatic mice, but also alleviated its recurrence by diminishing CD8+ central memory T (TCM) and CD8+ resident memory T (TRM) cells. It attenuated epidermal pathology and T-cell infiltration in the skin of IMQ-induced psoriatic mice while suppressing expression of IL-15, IL-17 and other proinflammatory cytokines in the skin. Surprisingly, DHA reduced the frequency and number of CD8+, but not CD4+, subset of CD44highCD62Lhigh TCM in psoriatic mice, whereas methotrexate (MTX) lowered CD4+, but not CD8+, TCM frequency and number. Indeed, DHA, but not MTX, downregulated eomesodermin (EOMES) and BCL-6 expression in CD8+ T-cells. Furthermore, DHA, but not MTX, reduced the presence of CD8+CLA+, CD8+CD69+ or CD8+CD103+ TRM cells in mouse skin. Interestingly, treatment with DHA, but not MTX, during the first onset of psoriasis largely prevented psoriasis relapse induced by low doses of IMQ two weeks later. Administration of recombinant IL-15 or CD8+, but not CD4+, TCM cells resulted in complete recurrence of psoriasis in mice previously treated with DHA. Finally, we demonstrated that DHA alleviated psoriatic human skin lesions in humanized NSG mice grafted with lesional skin from psoriatic patients while reducing human CD8+ TCM and CD103+ TRM cells in humanized mice. Conclusion: We have provided the first evidence that DHA is advantageous over MTX in preventing psoriasis relapse by reducing memory CD8+ T-cells.

Development and characterization of a human Th17-driven ex vivo skin inflammation model.

Skin models mimicking features of psoriasis-related inflammation are needed to support the development of new drugs in dermatology. Reconstructed skin models lack tissue complexity, including a fully competent skin barrier, and presence and/or diversity of immune cells. Here, we describe InflammaSkin®, a novel human Th17-driven ex vivo skin inflammation model. In this model, skin-resident T cells are in situ activated by intradermal injection of anti-CD3 and anti-CD28 antibodies and Th17 cell polarization is sustained by culture in a chemically defined medium supplemented with IL-1ß, IL-23 and TGF-ß for seven days. The acquired Th17 signature is demonstrated by the sustained secretion of IL-17A, IL-17AF, IL-17F, IL-22, IFN-γ, and to some degree IL-15 and TNF-α observed in the activated ex vivo skin inflammation model compared with the non-activated skin model control. Furthermore, expression of S100A7 and Keratin-16 by keratinocytes and loss of epidermal structure integrity occur subsequently to in situ Th17cell activation, demonstrating cellular crosstalk between Th17 cells and keratinocytes. Finally, we demonstrate the use of this model to investigate the modulation of the IL-23/IL-17 immune axis by topically applied anti-inflammatory compounds. Taken together, we show that by in situ activation of skin-resident Th17 cells, the InflammaSkin® model reproduces aspects of inflammatory responses observed in psoriatic lesions and could be used as a translational tool to assess efficacy of test compounds.

Vitamin A or E and a catechin synergize as vaccine adjuvant to enhance immune responses in mice by induction of early interleukin-15 but not interleukin-1ß responses.

Vitamins A and E and select flavonoids in the family of catechins are well-defined small molecules that, if proven to possess immunomodulatory properties, hold promise as vaccine adjuvants and various therapies. In an effort to determine the in vivo immunomodulatory properties of these molecules, we found that although mucosal and systemic vaccinations with a recombinant HIV-1BaL gp120 with either a catechin, epigallo catechin gallate (EGCG) or pro-vitamin A (retinyl palmitate) alone in a vegetable-oil-in-water emulsion (OWE) suppressed antigen-specific responses, the combination of EGCG and vitamin A or E in OWE (Nutritive Immune-enhancing Delivery System, NIDS) synergistically enhanced adaptive B-cell, and CD4(+) and CD8(+) T-cell responses, following induction of relatively low local and systemic innate tumour necrosis factor-α (TNF-α), interleukin-6 (IL-6) and IL-17, but relatively high levels of early systemic IL-15 responses. For induction of adaptive interferon-γ and TNF-α responses by CD4(+) and CD8(+) T cells, the adjuvant effect of NIDS was dependent on both IL-15 and its receptor. In addition, the anti-oxidant activity of NIDS correlated positively with higher expression of the superoxide dismutase 1, an enzyme involved in reactive oxygen species elimination but negatively with secretion of IL-1ß. This suggests that the mechanism of action of NIDS is dependent on anti-oxidant activity and IL-15, but independent of IL-1ß and inflammasome formation. These data show that this approach in nutritive vaccine adjuvant design holds promise for the development of potentially safer effective vaccines.

Isotretinoin Exposure and Risk of Celiac Disease.

BACKGROUND: Isotretinoin (13-cis retinoic acid) is a metabolite of vitamin A and has anti-inflammatory and immunoregulatory effects; however, a recent publication by DePaolo et al. demonstrated that in the presence of IL-15, retinoic acid can act as an adjuvant and promote inflammation against dietary proteins. OBJECTIVE: To evaluate the risk of overt and latent celiac disease (CD) among users of isotretinoin. MATERIAL AND METHODS: Medical records of patients from 1995 to 2011 who had a mention of isotretinoin in their records (N = 8393) were searched for CD diagnosis using ICD-09CM codes. Isotretinoin exposure was compared across overt CD patients and their age- and gender-matched controls from the same pool. To evaluate the risk of latent CD with isotretinoin exposure, patients were overlapped with a community-based list of patients with waste serum samples that were tested for CD serology, excluding those with overt CD (2006-2011). Isotretinoin exposure was defined as the use of isotretinoin prior to CD diagnosis or serology. RESULTS: Of 8393 patients, 25 had a confirmed CD diagnosis. Compared to matched controls (N = 75), isotretinoin exposure was not significantly different between overt CD patients versus controls (36% versus 39%, respectively; P = 0.712). Likewise, latent CD defined as positive serology was not statistically different between isotretinoin exposed (N = 506) versus non-exposed (N = 571) groups (1.8% versus 1.4%, respectively; P = 0.474). CONCLUSIONS: There was no association between isotretinoin use and risk of either overt or latent CD.

Recognition of gut microbiota by NOD2 is essential for the homeostasis of intestinal intraepithelial lymphocytes.

NOD2 functions as an intracellular sensor for microbial pathogen and plays an important role in epithelial defense. The loss-of-function mutation of NOD2 is strongly associated with human Crohn's disease (CD). However, the mechanisms of how NOD2 maintains the intestinal homeostasis and regulates the susceptibility of CD are still unclear. Here we found that the numbers of intestinal intraepithelial lymphocytes (IELs) were reduced significantly in Nod2(-/-) mice and the residual IELs displayed reduced proliferation and increased apoptosis. Further study showed that NOD2 signaling maintained IELs via recognition of gut microbiota and IL-15 production. Notably, recovery of IELs by adoptive transfer could reduce the susceptibility of Nod2(-/-) mice to the 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis. Our results demonstrate that recognition of gut microbiota by NOD2 is important to maintain the homeostasis of IELs and provide a clue that may link NOD2 variation to the impaired innate immunity and higher susceptibility in CD.

Attenuation of rat chronic small bowel allograft rejection by n-3 polyunsaturated fatty acids is associated with reduced expression of graft IL-15.

Interleukin-15 was found to play key roles in various immunological processes including chronic rejection after renal and cardiac transplantation. n-3 polyunsaturated fatty acids (n-3 PUFA) have shown beneficial effects to chronic allograft rejection. The objective of this study is to search the possible mechanism of this inhibitory effect in chronic small bowel allograft rejection. Animals were divided into three groups: isograft (CsA + corn oil-supplemented diet); allograft (CsA + corn oil-supplemented diet); and allograft (CsA + fish oil-supplemented diet). Donor intestines from F344 rats were transplanted orthotopically into Lewis rat recipients. CsA was administered at 5 mg/kg/day for 2 wk post-operatively. Post-transplant weight was recorded. Histopathological changes and graft IL-15 expression were measured on POD 90. Chronic small bowel allograft rejection developed on POD 90. n-3 PUFA significantly decreased the score of chronic rejection and increased the post-operative weight gain rate. This attenuation is associated with reduced graft IL-15 expression. n-3 PUFA contributed to improved pathological and clinical outcome during chronic small bowel allograft rejection, and this improvement was associated with reduced graft IL-15 expression.

Fish oil attenuates omega-6 polyunsaturated fatty acid-induced dysbiosis and infectious colitis but impairs LPS dephosphorylation activity causing sepsis.

Clinically, excessive ω-6 polyunsaturated fatty acid (PUFA) and inadequate ω-3 PUFA have been associated with enhanced risks for developing ulcerative colitis. In rodent models, ω-3 PUFAs have been shown to either attenuate or exacerbate colitis in different studies. We hypothesized that a high ω-6: ω-3 PUFA ratio would increase colitis susceptibility through the microbe-immunity nexus. To address this, we fed post-weaned mice diets rich in ω-6 PUFA (corn oil) and diets supplemented with ω-3 PUFA (corn oil+fish oil) for 5 weeks. We evaluated the intestinal microbiota, induced colitis with Citrobacter rodentium and followed disease progression. We found that ω-6 PUFA enriched the microbiota with Enterobacteriaceae, Segmented Filamentous Bacteria and Clostridia spp., all known to induce inflammation. During infection-induced colitis, ω-6 PUFA fed mice had exacerbated intestinal damage, immune cell infiltration, prostaglandin E2 expression and C. rodentium translocation across the intestinal mucosae. Addition of ω-3 PUFA on a high ω-6 PUFA diet, reversed inflammatory-inducing microbial blooms and enriched beneficial microbes like Lactobacillus and Bifidobacteria, reduced immune cell infiltration and impaired cytokine/chemokine induction during infection. While, ω-3 PUFA supplementation protected against severe colitis, these mice suffered greater mortality associated with sepsis-related serum factors such as LPS binding protein, IL-15 and TNF-α. These mice also demonstrated decreased expression of intestinal alkaline phosphatase and an inability to dephosphorylate LPS. Thus, the colonic microbiota is altered differentially through varying PUFA composition, conferring altered susceptibility to colitis. Overall, ω-6 PUFA enriches pro-inflammatory microbes and augments colitis; but prevents infection-induced systemic inflammation. In contrast, ω-3 PUFA supplementation reverses the effects of the ω-6 PUFA diet but impairs infection-induced responses resulting in sepsis. We conclude that as an anti-inflammatory agent, ω-3 PUFA supplementation during infection may prove detrimental when host inflammatory responses are critical for survival.

A comparative study of stress-mediated immunological functions with the adjuvanticity of alum.

The efficacy of a vaccine is generally dependent on an adjuvant, which enhances the immune functions and alum has been widely used in human immunization. Alum activates the intracellular stress sensors inflammasomes, but whether these are responsible for the adjuvanticity is controversial. The objectives of this investigation were to examine the hypothesis that alum-mediated adjuvanticity is a function of stress and conversely that stress agents will elicit adjuvanticity. The investigation was carried out in BALB/c mice by SC immunization with ovalbumin (OVA) mixed with alum. This elicited inflammasomes, with significant activation of caspase 1, production of IL-1ß, and adjuvanticity, demonstrated by enhancing OVA-specific serum IgG antibodies, CD4(+) T cells, and proliferation. The novel finding that alum induced HSP70 suggests that stress is involved in the mechanism of adjuvanticity. This was confirmed by inhibition studies with PES (phenylethynesulfonamide), which disrupts inducible HSP70 function, and inhibited both inflammasomes and the adjuvant function. Parallel studies were pursued with an oxidative agent (sodium arsenite), K-releasing agent (Gramicidin) and a metal ionophore (dithiocarbamate). All 3 stress agents induced HSP70, inflammasomes, and the adjuvant functions. Furthermore, up-regulation of membrane associated IL-15 on DC and CD40L on T cells in the animals treated with alum or the stress agents mediate the interactions between splenic CD11c DC and CD4(+) or CD8(+) T cells. The results suggest that the three stress agents elicit HSP70, a hallmark of stress, as well as inflammasomes and adjuvanticity, commensurate with those of alum, which may provide an alternative strategy in developing novel adjuvants.

Immune responses induced by Pelargonium sidoides extract in serum and nasal mucosa of athletes after exhaustive exercise: modulation of secretory IgA, IL-6 and IL-15.

The evidence that exhaustive exercise may compromise the immune response is mainly confirmed by upper respiratory tract infections which are probably related to the decrease in secretory immunoglobulin A in the upper airway mucosa and/or profile changes of systemic cytokines as well as local cytokines of the upper respiratory tract. An extract from Pelargonium sidoides roots is currently used to treat infections in the upper airways. The aim of the present study was to evaluate the action of this herbal medicine on the immune response of athletes submitted to an intense running session by analyzing the production of immunoglobulin A in their saliva and of cytokines both locally and systemically, using a placebo as control. The results show that Pelargonium sidoides extract modulates the production of secretory immunoglobulin A in saliva, both interleukin-15 and interleukin-6 in serum, and interleukin-15 in the nasal mucosa. Secretory immunoglobulin A levels were increased, while levels of IL-15 and IL-6 were decreased. Based on this evidence, we suggest that this herbal medicine can exert a strong modulating influence on the immune response associated with the upper airway mucosa in athletes submitted to intense physical activity.

IL-15 receptor deletion results in circadian changes of locomotor and metabolic activity.

Interleukin-15 (IL-15) is a cytokine produced in the normal brain that acts on its specific receptor IL-15Ralpha and co-receptors IL-2Rbeta and IL-2Rgamma in neuronal cells. The functions of the cerebral IL-15 system, however, are not yet clear. To test the hypothesis that IL-15Ralpha regulates metabolic activity and body temperature, we quantified the specific metabolic phenotype of IL-15Ralpha knockout mice. These normal-appearing mice were leaner with lower fat composition. During the entire circadian cycle, the knockout mice had a significantly higher acrophase in locomotor activity and heat dissipation. During the light phase, there was significantly greater food intake, oxygen consumption, and carbon dioxide production. The difference in the dark and light phases suggests that IL-15Ralpha participates in circadian rhythm regulation. The higher oxygen consumption in the light phase indicates adaptive thermogenesis in the knockout mice. The body temperature of the receptor knockout mice was significantly higher than the control in the light phase, and this was mainly caused by a large difference occurring between 0600 and 0900 h. In addition to the metabolic chamber studies and circadian rhythm analyses, qPCR of hypothalamic homogenates indicated higher mRNA expression of orexin and transient receptor potential vanilloid 4 cation channels. Consistent with a direct role of IL-15Ralpha in the hypothalamus, IL-15 treatment of the wild-type mice induced c-Fos expression in the preoptic area. We conclude that activation of hypothalamic neurons by IL-15 in mice contributes to thermoregulation and modifies the metabolic phenotype.

[Selenium deficiency in celiac disease: risk of autoimmune thyroid diseases]. / Carenza di selenio nella malattia celiaca: rischio di tireopatie autoimmuni.

The essential trace mineral selenium is of fundamental importance to human health. It is incorporated in the proteome in the forms of the genetically encoded amino acids selenocysteine and selenomethionine, which are the characteristic components of selenoproteins (SeP) such as glutathione peroxidases (GPx), thioredoxin reductases and iodothyronine deiodinase families. Thyroid is especially sensitive to selenium deficiency, because SeP can modify thyreocytes function by acting as antioxidants and modifying redox status and thyroid hormone metabolism. SeP are also involved in apoptosis, cell growth and modification of the action of cell signalling systems and transcription factors. Some intestinal GPx modulate apoptosis by removing the cells affected by oxidative damage preserving tissue integrity. The malfunctioning of the GPx antioxidant system in intestinal mucosa can trigger a continuous cycle of reactive oxygen species and inflammation. Selenium deficiency is a risk factor, due to the malabsorption, in celiac disease (CD) because the inflammatory damage affects the small intestine; this deficiency can modulate SeP genes expression, with consequent reiteration of inflammation and increase of mucosal damage. In active CD, overexpression of interleukin-15 (IL-15) may increase activation of effector mechanisms of epithelial damage by stimulating T helper 1 cytokine proliferation and production and intraepithelial lymphocytes cytotoxicity by protecting these lymphocytes from apoptosis. Blocking IL-15 has the potential to provide new therapeutic tools to prevent both tissue damage and complication of CD such as autoimmune thyroid diseases (AITD) where IL-15 expression is also increases. In view of the role played by SeP in apoptosis inhibition, the presence of environmental factors such as selenium deficiency can be considered an important direct factor of thyroidal damage in development of AITD.

Interleukin-15 and interferon-gamma participate in the cross-talk between natural killer and monocytic cells required for tumour necrosis factor production.

We have characterized the lymphocyte subset and the receptor molecules involved in inducing the secretion of TNF by monocytic cells in vitro. The TNF secreted by monocytic cells was measured when they were co-cultured with either resting or IL-15-stimulated lymphocytes, T cells, B cells or natural killer (NK) cells isolated from the peripheral blood of healthy subjects and from the synovial fluid from patients with inflammatory arthropathies. Co-culture with IL-15-activated peripheral blood or synovial fluid lymphocytes induced TNF production by monocytic cells within 24 hours, an effect that was mainly mediated by NK cells. In turn, monocytic cells induced CD69 expression and IFN-gamma production in NK cells, an effect that was mediated mainly by beta2 integrins and membrane-bound IL-15. Furthermore, IFN-gamma increased the production of membrane-bound IL-15 in monocytic cells. Blockade of beta2 integrins and membrane-bound IL-15 inhibited TNF production, whereas TNF synthesis increased in the presence of anti-CD48 and anti-CD244 (2B4) monoclonal antibodies. All these findings suggest that the cross-talk between NK cells and monocytes results in the sustained stimulation of TNF production. This phenomenon might be important in the pathogenesis of conditions such as rheumatoid arthritis in which the synthesis of TNF is enhanced.

Structural basis for binding multiple ligands by the common cytokine receptor gamma-chain.

The common gamma-chain (gamma(c)) that functions both in ligand binding and signal transduction is a shared subunit of the multichain receptors for interleukin (IL)-2, IL-4, IL-7, IL-9, IL-15, and IL-21. The structural basis by which the ectodomain of gamma(c) contributes to binding six distinct cytokines is only partially defined. In the present study, epitope mapping of antagonistic anti-gamma(c) monoclonal antibodies led to the identification of Asn-128 of mouse gamma(c) that represents another potential contact residue that is required for binding IL-2, IL-7, and IL-15 but not IL-4. In addition, Tyr-103, Cys-161, Cys-210, and Cys-211, previously identified to contribute to binding IL-2 and IL-7, were also found to be involved in binding IL-4 and IL-15. Collectively, these data favor a model in which gamma(c) utilizes a common mechanism for its interactions with multiple cytokines, and the binding sites are largely overlapping but not identical. Asn-128 and Tyr-103 likely act as contact residues whereas Cys-161, Cys-210, and Gly-211 may stabilize the structure of the proposed ligand-interacting surface formed by the two extracytoplasmic domains.