Lipopolysaccharide promotes and augments metal allergies in mice, dependent on innate immunity and histidine decarboxylase

Allergenicity and Bioavailability of Nickel Nanoparticles Compared to Nickel Microparticles in Mice

Metal allergy is a common disease that afflicts many people. Nevertheless, the mechanism underlying metal allergy development has not been completely elucidated. Metal nanoparticles might be involved in the development of a metal allergy, but the associated details are unknown. In this study, we evaluated the pharmacokinetics and allergenicity of nickel nanoparticles (Ni-NPs) compared with those of nickel microparticles (Ni-MPs) and nickel ions. After characterizing each particle, the particles were suspended in phosphate-buffered saline and sonicated to prepare a dispersion. We assumed the presence of nickel ions for each particle dispersion and positive control and orally administered nickel chloride to BALB/c mice repeatedly for 28 days. Results showed that compared with those in the Ni-MP administration group (MP group), the Ni-NP administration group (NP group) showed intestinal epithelial tissue damage, elevated serum interleukin (IL)-17 and IL-1β levels, and higher nickel accumulation in the liver and kidney. Additionally, transmission electron microscopy confirmed the accumulation of Ni-NPs in the livers of both the NP and nickel ion administration groups. Furthermore, we intraperitoneally administered a mixed solution of each particle dispersion and lipopolysaccharide to mice and then intradermally administered nickel chloride solution to the auricle after 7 days. Swelling of the auricle was observed in both the NP and MP groups, and an allergic reaction to nickel was induced. Particularly in the NP group, significant lymphocytic infiltration into the auricular tissue was observed, and serum IL-6 and IL-17 levels were increased. The results of this study showed that in mice, Ni-NP accumulation in each tissue was increased after oral administration and toxicity was enhanced, as compared to those with Ni-MPs. Orally administered nickel ions transformed into nanoparticles with a crystalline structure and accumulated in tissues. Furthermore, Ni-NPs and Ni-MPs induced sensitization and nickel allergy reactions in the same manner as that with nickel ions, but Ni-NPs induced stronger sensitization. Additionally, the involvement of Th17 cells was suspected in Ni-NP-induced toxicity and allergic reactions. In conclusion, oral exposure to Ni-NPs results in more serious biotoxicity and accumulation in tissues than Ni-MPs, suggesting that the probability of developing an allergy might increase.

Examination of colorectal cancer cases with metal allergy

PURPOSE

To report our initiatives and treatment results for patients with colorectal cancer with metal allergy.

METHODS

A total of 27 patients (2.6%) with a history of metal contact dermatitis were identified among 1027 patients who underwent curative resection of colorectal cancer from 2014 to 2020. The results of the patch test, perioperative results, and postoperative colonoscopy findings were also investigated.

RESULTS

The patch test for metal allergens and staples was performed in 21 patients (77.8%), and 13 of them (61.9%) tested positive for at least one metal allergen. Ni (38.1%), Co (28.6%), and Pd (19.0%) showed higher positive rates than other metals, and 1 patient (4.8%) tested positive for staples. Stapled anastomosis/suturing was performed as planned in 15 of 27 patients. In 10 patients, the anastomosis method was changed from stapled to hand-sewn according to the no-patch test results (60%), positivity for multiple metals (20%), positivity for staples (10%), and surgeon's judgment (10%). No complications and abnormal colonoscopy findings were found to be associated with stapled anastomosis/suturing.

CONCLUSION

The patch test is useful for selecting an optimal anastomosis method for patients with suspected metal allergy.

The enhancement effect of low-dose dietary lipopolysaccharide on the growth and immunity of Litopenaeus vannamei, and transcriptome analysis

In this study, the effects of dietary lipopolysaccharide (LPS) on Litopenaeus vannamei were investigated to determine whether LPS could play a role as a potential immunostimulant in shrimp. L. vannamei with an initial body weight of 0.30 ± 0.02 g were fed a diet containing LPS at doses of 0, 0.2, 1, 5, 25 or 125 mg kg^-1 for eight weeks (groups LPS0, LPS0.2, LPS1, LPS5, LPS25 and LPS125, respectively). After eight weeks of feeding, the growth performance, immunity and transcriptome response of L. vannamei were analysed. Only dietary LPS at 0.2 and 1 mg kg^-1 resulted in a significant increase in the growth of L. vannamei (P < 0.05). According to the weight gain rate (WGR) and specific growth rate (SGR), the optimum dietary LPS level was 2.462 and 2.455 mg kg^-1, respectively. When compared with the control group, the survival rate (SR) of L. vannamei in the LPS0.2 group was significantly increased after white spot syndrome virus (WSSV) infection and the SR of L. vannamei in the LPS1 group was significantly increased after Vibrio parahaemolyticus infection (both P < 0.05). Compared with the LPS0 group, immune enzyme activity in the serum of L. vannamei could be significantly increased and the content of maleic dialdehyde (MDA) significantly decreased by dietary LPS. Transcriptome analysis of the haemocytes of L. vannamei identified 399 up-regulated differentially expressed genes (DEGs) and 5000 down-regulated DEGs in the LPS0.2 compared to the control group. Most of the DEGs were significantly enriched in the following pathways: phosphatidylinositol signalling, Wnt signalling, Jak-STAT signalling and inositol phosphate metabolism. In conclusion, this study revealed that diets supplemented with low-dose LPS had positive effects on the growth and immunity of L. vannamei.

Rab44 Deficiency Induces Impaired Immune Responses to Nickel Allergy

Rab44 was recently identified as an atypical Rab GTPase that possesses EF-hand and coiled-coil domains at the N-terminus, and a Rab-GTPase domain at the C-terminus. Rab44 is highly expressed in immune-related cells such as mast cells, macrophages, osteoclasts, and granulocyte-lineage cells in the bone marrow. Therefore, it is speculated that Rab44 is involved in the inflammation and differentiation of immune cells. However, little is known about the role of Rab44 in inflammation. In this study, we showed that Rab44 was upregulated during the early phase of differentiation of M1- and M2-type macrophages. Rab44-deficient mice exhibited impaired tumor necrosis factor alpha and interleukin-10 production after lipopolysaccharide (LPS) stimulation. The number of granulocytes in Rab44-deficient mice was lower, but the lymphocyte count in Rab44-deficient mice was significantly higher than that in wild-type mice after LPS stimulation. Moreover, Rab44-deficient macrophages showed impaired nickel-induced toxicity, and Rab44-deficient mice showed impaired nickel-induced hypersensitivity. Upon nickel hypersensitivity induction, Rab44-deficient mice showed different frequencies of immune cells in the blood and ears. Thus, it is likely that Rab44 is implicated in immune cell differentiation and inflammation, and Rab44 deficiency induces impaired immune responses to nickel allergies.

Immune response differences in degradable and non-degradable alloy implants

Alloy based implants have made a great impact in the clinic and in preclinical research. Immune responses are one of the major causes of failure of these implants in the clinic. Although the immune responses toward non-degradable alloy implants are well documented, there is a poor understanding of the immune responses against degradable alloy implants. Recently, there have been several reports suggesting that degradable implants may develop substantial immune responses. This phenomenon needs to be further studied in detail to make the case for the degradable implants to be utilized in clinics. Herein, we review these new recent reports suggesting the role of innate and potentially adaptive immune cells in inducing immune responses against degradable implants. First, we discussed immune responses to allergen components of non-degradable implants to give a better overview on differences in the immune response between non-degradable and degradable implants. Furthermore, we also provide potential areas of research that can be undertaken that may shed light on the local and global immune responses that are generated in response to degradable implants.

Autophagy involvement in T lymphocyte signalling induced by nickel with quantitative phosphoproteomic analysis

Nickel-induced allergic contact dermatitis (ACD) is a common skin disease. The mechanism by which nickel causes ACD is not clear. There is no treatment for it, only symptomatic therapy. However, due to the lifetime sensitization characteristics, the recurrence rate in patients is high. T lymphocytes play a key role in nickel-induced ACD. Elucidating the potential mechanism underlying nickel-induced T lymphocyte signalling might make it possible to achieve targeted treatment of nickel-induced ACD. In our study, a phosphoproteomic approach based on tandem mass tag (TMT) labelling and LCMS/MS analyses was employed. An animal model of nickel allergy was established. Splenic T lymphocytes were purified for quantitative phosphoproteomic analysis. The numbers of phosphoproteins, phosphopeptides and phosphosites identified in this study were 3072, 7977 and 10,200, respectively. Comprehensive gene ontology (GO) analysis combined with Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis revealed that nickel can significantly affect the phosphorylation of the mTOR signalling pathway in T lymphocytes. Western blotting analysis was used to detect changes in the expression of autophagy-related proteins (Beclin 1, LC3II, and p62). Nickel allergy changed autophagy-related protein expression (p < 0.05). It has been demonstrated that nickel causes autophagy of T lymphocytes in the spleen. Using autophagy inhibitors to intervene, it was found that Th1 differentiation was inhibited, and the expression of Th1-related inflammatory factors was downregulated. Overall, the identification of relevant signalling pathways yielded new insights into the molecular mechanisms underlying nickel allergy and might help in the discovery and development of mechanism-based drugs.

Metal-induced delayed type hypersensitivity responses potentiate particle induced osteolysis in a sex and age dependent manner

It is widely recognized that innate macrophage immune reactions to implant debris are central to the inflammatory responses that drive biologic implant failure over the long term. Less common, adaptive lymphocyte immune reactions to implant debris, such as delayed type hypersensitivity (DTH), can also affect implant performance. It is unknown which key patient factors, if any, mediate these adaptive immune responses that potentiate particle/macrophage mediated osteolysis. The objective of this investigation was to determine to what degree known adaptive immune responses to metal implant debris can affect particle-induced osteolysis (PIO); and if this pathomechanism is dependent on: 1) innate immune danger signaling, i.e., NLRP3 inflammasome activity, 2) sex, and/or 3) age. We used an established murine calvaria model of PIO using male and female wild-type C57BL/6 vs. Caspase-1 deficient mice as well as young (12–16 weeks old) vs. aged (18–24 months old) female and male C57BL/6 mice. After induction of metal-DTH, and Cobalt-alloy particle (ASTM F-75, 0.4um median diameter) calvaria challenge, bone resorption was assessed using quantitative micro-computed tomography (micro-CT) analysis and immune responses were assessed by measuring paw inflammation, lymphocyte transformation test (LTT) reactivity and adaptive immune cytokines IFN-gamma and IL-17 (ELISA). Younger aged C57BL/6 female mice exhibited the highest rate and severity of metal sensitivity lymphocyte responses that also translated into higher PIO compared to any other experimental group. The absence of inflammasome/caspase-1 activity significantly suppressed DTH metal-reactivity and osteolysis in both male and female Caspase-1 deficient mice. These murine model results indicate that young female mice are more predisposed to metal-DTH augmented inflammatory responses to wear debris, which is highly influenced by active NLRP3 inflammasome/caspase-1 danger signaling. If these results are clinically meaningful for orthopedic patients, then younger female individuals should be appropriately assessed and followed for DTH derived peri-implant complications.

Differential influence of Streptococcus mitis on host response to metals in reconstructed human skin and oral mucosa

BACKGROUND

Skin and oral mucosa are continuously exposed to potential metal sensitizers while hosting abundant microbes, which may influence the host response to sensitizers. This host response may also be influenced by the route of exposure that is skin or oral mucosa, due to their different immune properties.

OBJECTIVE

Determine how commensal Streptococcus mitis influences the host response to nickel sulfate (sensitizer) and titanium(IV) bis(ammonium lactato)dihydroxide (questionable sensitizer) in reconstructed human skin (RHS) and gingiva (RHG).

METHODS

RHS/RHG was exposed to nickel or titanium, in the presence or absence of S. mitis for 24 hours. Histology, cytokine secretion, and Toll-like receptors (TLRs) expression were assessed.

RESULTS

S. mitis increased interleukin (IL)-6, CXCL8, CCL2, CCL5, and CCL20 secretion in RHS but not in RHG; co-application with nickel further increased cytokine secretion. In contrast, titanium suppressed S. mitis-induced cytokine secretion in RHS and had no influence on RHG. S. mitis and metals differentially regulated TLR1 and TLR4 in RHS, and predominantly TLR4 in RHG.

CONCLUSION

Co-exposure of S. mitis and nickel resulted in a more potent innate immune response in RHS than in RHG, whereas titanium remained inert. These results indicate the important influence of commensal microbes and the route of exposure on the host's response to metals.

Pathogenic Mechanisms and Therapeutic Implication in Nickel-Induced Cell Damage

Background:

Nickel (Ni) is mostly applied in a number of industrial areas such as printing inks, welding, alloys, electronics and electrical professions. Occupational or environmental exposure to nickel may lead to cancer, allergy reaction, nephrotoxicity, hepatotoxicity, neurotoxicity, as well as cell damage, apoptosis and oxidative stress.

Methods:

In here, we focused on published studies about cell death, carcinogenicity, allergy reactions and neurotoxicity, and promising agents for the prevention and treatment of the toxicity by Ni.

Results:

Our review showed that in the last few years, more researches have focused on reactive oxygen species formation, oxidative stress, DNA damages, apoptosis, interaction with involving receptors in allergy and mitochondrial damages in neuron induced by Ni.

Conclusion:

The collected data in this paper provide useful information about the main toxicities induced by Ni, also, their fundamental mechanisms, and how to discover new ameliorative agents for prevention and treatment by reviewing agents with protective and therapeutic consequences on Ni induced toxicity.

Migratory dendritic cells in skin-draining lymph nodes have nickel-binding capabilities

Nickel (Ni) is the most frequent metal allergen and induces Th1-dependent type-IV allergies. In local skin, epidermal Langerhans cells (LCs) and/or dermal dendritic cells (DCs) uptake antigens and migrate to draining lymph nodes (LNs). However, the subsets of antigen-presenting cells that contribute to Ni presentation have not yet been identified. In this study, we analyzed the Ni-binding capabilities of murine DCs using fluorescent metal indicator Newport Green. Elicitation of Ni allergy was assessed after intradermal (i.d.) injection of Ni-treated DCs into ear pinnae of Ni-sensitized mice. The Ni-binding capabilities of MHC class II^hi CD11c^int migratory DCs were significantly stronger than those of MHC class II^int CD11c^hi resident DCs and CD11c^int PDCA1⁺ MHC class II^int B220⁺ plasmacytoid DCs. Migratory DCs in skin-draining and mandibular LNs showed significantly stronger Ni-binding capabilities than those in mesenteric and medial iliac LNs. An i.d. injection of IL-1β induced the activation of LCs and dermal DCs with strong Ni-binding capabilities. Ni-binding LCs were detected in draining LNs after i.d. challenge with IL-1β and Ni. Moreover, an i.d. injection of Ni-treated DCs purified from skin-draining LNs elicited Ni-allergic inflammation. These results demonstrated that migratory DCs in skin-draining LNs have strong Ni-binding capabilities and elicit Ni allergy.

Effect of scaling and root planing on level of immunoglobulin E and immunoglobulin G4 in children with gingivitis and house-dust mite allergy: A pilot randomised controlled trial

Background and Objective: There is a pressing need for developing innovative strategies to prevent allergic diseases among children. As house-dust mite (HDM) allergy is often seen in children with gingivitis, strategies should be derived from a conceptual framework of allergen elimination and pathogen eradication; one such strategy is dental scaling and root planing (SRP) to remove dental plaque and periodontal pathogens. The study aimed to evaluate the beneficial effects of comprehensive 6-months dental SRP to reduce the level of immunoglobulin E (IgE) and immunoglobulin G₄ (IgG₄) in children with gingivitis and HDM allergy. IgE and IgG₄, whose production is controlled mainly by Th-2 cells and B cells, are proven biomarkers for atopic inflammatory responses. Methods: The present study conducted a non-blinded randomised controlled trial with superiority design. A total of 10 subjects (age range 6-16 years) with gingivitis and positive skin-prick test to HDM from Pediatric Allergy Outpatient Clinic, Dr. Soetomo General Hospital were enrolled in the present study. Of the 10 subjects, only five received dental SRP. We further evaluated total serum IgE and IgG₄ level before and 6 months after treatment. Results and Discussion: Subjects in the standard treatment group showed a slight decrease in the IgE level ([Formula: see text]) but no change in the IgG₄ level ([Formula: see text]), while subjects in the intervention group showed a significant decrease in IgE ([Formula: see text]) and IgG₄ levels ([Formula: see text]). Conclusion: The study results suggest that 6-month comprehensive dental scaling combined with root planing may help to reduce IgE and IgG₄ levels in children with gingivitis and HDM allergy. Furthermore, untreated or undertreated gingivitis is often associated with worsening allergic manifestation and thus should be avoided. Trial Registration: ISRCTN31416107, retrospectively registered on 17 April 2018.

Developments in the field of allergy in 2017 through the eyes of Clinical and Experimental Allergy

In this article, we described the development in the field of allergy as described by Clinical and Experimental Allergy in 2017. Experimental models of allergic disease, basic mechanisms, clinical mechanisms, allergens, asthma and rhinitis and clinical allergy are all covered.

COX-2 induces T cell accumulation and IFN-γ production during the development of chromium allergy

Chromium (Cr) is commonly added into various metal alloys to improve some mechanical properties such as corrosion resistance, strength, and workability. However, Cr is also known to be a metal allergen for some individuals. Metal allergy is a T cell-mediated disease with symptoms of inflammation and swelling that involve inflammatory cytokines and prostaglandins. Hence, suppressing these inflammation paths by using COX-2 inhibitor might be useful in treating Cr allergy. In this study, mice were used with Cr-induced allergy challenge model. The mice were injected with celecoxib once per day for 7 days one hour after the challenge. Footpad samples were stained with haematoxylin and eosin (H&E), and lymphocytes were isolated from popliteal lymph nodes for the flow cytometric analysis. The results show that both prostaglandin E₂ (PGE₂), a known mediator of inflammation, and cyclooxygenases (COX)-2 have important roles in the development of Cr allergy. Further, COX-2 inhibitor, celecoxib, was effective in relieving swelling and inflammation in Cr-allergic mice concordant with suppression of IFN-γ production by CD8⁺ T cells and T cell accumulation in the lymph nodes. Therefore, the inhibition of COX-2 may be a therapeutic target for Cr allergy, and additional molecules in the PGE₂ signalling pathway may also be an effective therapeutic target for the treatment of metal allergy.

Interleukin-1 and histamine are essential for inducing nickel allergy in mice

BACKGROUND

We previously reported that (a) lipopolysaccharide (LPS) is a potent adjuvant for inducing Nickel (Ni) allergy in mice at both the sensitization and elicitation steps, (b) LPS induces Interleukin-1 (IL-1) and histidine decarboxylase (HDC, the histamine-forming enzyme), and IL-1 induces HDC, (c) Ni allergy is induced in mast cell-deficient, but not IL-1-deficient (IL-1-KO) or HDC-KO mice.

OBJECTIVE

To examine the roles of IL-1 and HDC (or histamine) and their interrelationship during the establishment of Ni allergy.

METHODS

Ni (NiCl₂ ) 1 mmol/L containing IL-1β and/or histamine was injected intraperitoneally (sensitization step). Ten days later, test substance(s) were intradermally injected into ear pinnas (elicitation step), and ear swelling was measured.

RESULTS

In wild-type mice, Ni + LPS or Ni + IL-1β injection at sensitization step followed by Ni alone at elicitation step induced Ni allergy. In IL-1-KO, injection of Ni + IL-1β (but not Ni + histamine) was required at both sensitization and elicitation steps to induce Ni allergy. In HDC-KO, Ni + IL-1β + histamine at sensitization step followed by Ni + histamine at elicitation step induced Ni allergy. In histamine H1 receptor-deficient mice, IL-1β induced HDC, but was ineffective as an adjuvant for inducing Ni allergy. In wild-type mice, injection into ear pinnas of Ni 10 mmol/L alone or Ni 1 mmol/L + LPS induced IL-1β, HDC and a prolonged swelling of ear pinnas. In non-sensitized mice, injection of IL-1β by itself into ear pinnas in IL-1-KO mice induced prolonged ear swelling. Ni augmented IL-1 production (both IL-1α and IL-1β) and HDC induction in wild-type mice sensitized to Ni.

CONCLUSIONS

In mice: (a) for inducing Ni allergy, IL-1 is essential at both the sensitization and elicitation steps, and HDC induction is involved in the effect of IL-1, (b) stimulation of H1 receptor is also essential for inducing Ni allergy at both sensitization and elicitation steps, and (c) the 'sensitization to Ni' state may be a state where tissues are primed for augmented production of IL-1α and/or IL-1β in response to Ni. (within 300 words, now 300).

Transition from metal-DTH resistance to susceptibility is facilitated by NLRP3 inflammasome signaling induced Th17 reactivity: Implications for orthopedic implants

Metal hypersensitivity has been recognized as an adverse biologic reaction that can compromise total joint arthroplasty (TJA) performance. However, the etiology of metal hypersensitivity responses in TJAs remains unclear. Metal implant debris is known to act as a danger signal that drives NLRP3 inflammasome activation. It remains unknown if implant debris induced inflammasome activation regulates T cell lineage in TJA metal hypersensitivity responses. In this study, we show both in vivo and in vitro that the pathogenesis of metal hypersensitivity responses to implant debris are largely dependent on activation of the inflammasome/caspase-1 pathway and subsequent production of IL-17A/F by CD4+ T cells. Inhibiting either the inflammasome pathway or IL-17A bioactivity in vivo and in vitro (in vivo using NLRP3 and Caspase-1 deficient mice or in vitro using blocking agents such as Capase-1 inhibitor, IL-1Ra and anti-IL-17A), significantly (p<0.05) mitigated metal-DTH paw inflammation as well as lymphocyte cytokine (IFN-γ and IL-17) and proliferation responses in metal-sensitized mice and primary human PBMCs. This study provides mechanistic insight into how in vivo exposure to orthopedic implant debris, and metals in general, elicits NLRP3 inflammasome activation that mediates the generation of IL-17A/F producing CD4+ T cells, leading to metal-delayed type hypersensitivity reactions.

Innate immunity and effector and regulatory mechanisms involved in allergic contact dermatitis

Skin's innate immunity is the initial activator of immune response mechanisms, influencing the development of adaptive immunity. Some contact allergens are detected by Toll-like receptors (TLRs) and inflammasome NLR3. Keratinocytes participate in innate immunity and, in addition to functioning as an anatomical barrier, secrete cytokines, such as TNF, IL-1β, and IL-18, contributing to the development of Allergic Contact Dermatitis. Dendritic cells recognize and process antigenic peptides into T cells. Neutrophils cause pro-inflammatory reactions, mast cells induce migration/maturation of skin DCs, the natural killer cells have natural cytotoxic capacity, the γδ T cells favor contact with hapten during the sensitization phase, and the innate lymphoid cells act in the early stages by secreting cytokines, as well as act in inflammation and tissue homeostasis. The antigen-specific inflammation is mediated by T cells, and each subtype of T cells (Th1/Tc1, Th2/Tc2, and Th17/Tc17) activates resident skin cells, thus contributing to inflammation. Skin's regulatory T cells have a strong ability to inhibit the proliferation of hapten-specific T cells, acting at the end of the Allergic Contact Dermatitis response and in the control of systemic immune responses. In this review, we report how cutaneous innate immunity is the first line of defense and focus its role in the activation of the adaptive immune response, with effector response induction and its regulation.

TRAV7-2*02 Expressing CD8⁺ T Cells Are Responsible for Palladium Allergy

While metallic biomaterials have led to an improvement in the quality of life, metal allergies, especially to palladium (Pd), has caused a recent increase in allergic patients. Metal allergy is known to be a T cell-mediated delayed-type hypersensitivity (DTH); however, the pathogenic T cell subsets and the specific T cell receptor (TCR) have not been identified. Therefore, we attempted to identify the pathogenic T cells responsible for Pd allergy. We found that activating CD8⁺ T cells significantly increased and that the TRAV (TCRα variable) 7-2*02 chain skewed in Pd allergic mice. Furthermore, adoptive transfer experiments revealed that in vitro-cultured Pd-stimulated antigen presenting cells (APCs) function as memory APCs with recipient mice developing Pd allergy and that the frequency of TRAV7-2*02 increases the same as conventional Pd allergic mice. In contrast, neither proliferation of CD8⁺ T cells nor increasing of TRAV7-2*02 was observed in major histocompatibility complex I (MHC I)-deficient Pd-APCs transferred to mice. Taken together, we revealed that TRAV7-2*02-expressing CD8⁺ T cells are the pathogenic T cells for the development of Pd allergy. We also identified the CDR3 consensus motif of pathogenic TCRs as CAAXSGSWQLIF in TRAV7-2*02/TRAJ (TCRα junction)22*01 positive cells. These results suggest that the specific TCRs represent novel targets for the development of diagnostics and treatments for metal allergy.

Induced histamine regulates Ni elution from an implanted Ni wire in mice by downregulating neutrophil migration

Histamine regulates various inflammatory reactions. We have reported that the expression of histidine decarboxylase (HDC) was induced by subcutaneous implantation of nickel (Ni) wire. However, the source and functions of histamine in Ni elution and Ni wire-induced inflammation have not been completely studied. We aimed to elucidate the effects of de novo synthesized histamine on leucocyte infiltration and Ni elution. Implantation of Ni wire induced an increase in the Ni ion content of the surrounding tissues and serum and in the mRNA levels of HDC, a histamine-producing enzyme, macrophage inflammatory protein-2 (MIP-2), a chemoattractant for neutrophils, and monocyte chemoattractant protein-1 (MCP-1), a chemoattractant for monocytes. The Ni wire induced HDC expression even in mast cell-deficient WBB6F1-W/W^V mice. In HDC knockout (HDC KO) mice, the Ni wire-induced increase in MIP-2 mRNA expression was significantly higher than that in wild-type mice but not MCP-1. MIP-2 expression was enhanced in histamine H2 receptor knockout (H2R KO) mice but not in WBB6F1-W/W^V mice. Histamine inhibited NiCl₂ -induced MIP-2 mRNA expression in mouse bone marrow-derived macrophages (BMDMs) obtained from wild-type mice; this inhibition was not observed in BMDMs from H2R KO mice. Ni elution increased in HDC KO mice, in which leucocyte infiltration also increased, and was suppressed in mice treated with neutrophil-specific antibody. These results suggest that the Ni wire induced HDC expression in non-mast cells and that, in the chronic phase of inflammation, endogenous histamine reduced Ni elution, probably through regulation of MIP-2 expression and neutrophil migration.

The mechanisms of nickel toxicity in aquatic environments: An adverse outcome pathway analysis

Current ecological risk assessment and water quality regulations for nickel (Ni) use mechanistically based, predictive tools such as biotic ligand models (BLMs). However, despite many detailed studies, the precise mechanism(s) of Ni toxicity to aquatic organisms remains elusive. This uncertainty in the mechanism(s) of action for Ni has led to concern over the use of tools like the BLM in some regulatory settings. To address this knowledge gap, the authors used an adverse outcome pathway (AOP) analysis, the first AOP for a metal, to identify multiple potential mechanisms of Ni toxicity and their interactions with freshwater aquatic organisms. The analysis considered potential mechanisms of action based on data from a wide range of organisms in aquatic and terrestrial environments on the premise that molecular initiating events for an essential metal would potentially be conserved across taxa. Through this analysis the authors identified 5 potential molecular initiating events by which Ni may exert toxicity on aquatic organisms: disruption of Ca²⁺ homeostasis, disruption of Mg²⁺ homeostasis, disruption of Fe^2+/3+ homeostasis, reactive oxygen species-induced oxidative damage, and an allergic-type response of respiratory epithelia. At the organ level of biological organization, these 5 potential molecular initiating events collapse into 3 potential pathways: reduced Ca²⁺ availability to support formation of exoskeleton, shell, and bone for growth; impaired respiration; and cytotoxicity and tumor formation. At the level of the whole organism, the organ-level responses contribute to potential reductions in growth and reproduction and/or alterations in energy metabolism, with several potential feedback loops between each of the pathways. Overall, the present AOP analysis provides a robust framework for future directed studies on the mechanisms of Ni toxicity and for developing AOPs for other metals. Environ Toxicol Chem 2017;36:1128-1137. © 2016 SETAC.

Allergic Responses Induced by the Immunomodulatory Effects of Nanomaterials upon Skin Exposure

Over the past decade, a vast array of nanomaterials has been created through the development of nanotechnology. With the increasing application of these nanomaterials in various fields, such as foods, cosmetics, and medicines, there has been concern about their safety, that is, nanotoxicity. Therefore, there is an urgent need to collect information about the biological effects of nanomaterials so that we can exploit their potential benefits and design safer nanomaterials, while avoiding nanotoxicity as a result of inhalation or skin exposure. In particular, the immunomodulating effect of nanomaterials is one of most interesting aspects of nanotoxicity. However, the immunomodulating effects of nanomaterials through skin exposure have not been adequately discussed compared with the effects of inhalation exposure, because skin penetration by nanomaterials is thought to be extremely low under normal conditions. On the other hand, the immunomodulatory effects of nanomaterials via skin may cause severe problems for people with impaired skin barrier function, because some nanomaterials could penetrate the deep layers of their allergic or damaged skin. In addition, some studies, including ours, have shown that nanomaterials could exhibit significant immunomodulating effects even if they do not penetrate the skin. In this review, we summarize our current knowledge of the allergic responses induced by nanomaterials upon skin exposure. First, we discuss nanomaterial penetration of the intact or impaired skin barrier. Next, we describe the immunomodulating effects of nanomaterials, focusing on the sensitization potential of nanomaterials and the effects of co-exposure of nanomaterials with substances such as chemical sensitizers or allergens, on the onset of allergy, following skin exposure. Finally, we discuss the potential mechanisms underlying the immunomodulating effects of nanomaterials by describing the involvement of the protein corona in the interaction of nanomaterials with biological components and by presenting recent data about the adjuvant effects of well-characterized particle adjuvant, aluminum salt, as an example of immunomodulatory particulate.

Promotion of Nickel (Ni) Allergy by Anamnestic Sensitization with a Bacterial Component, Lipopolysaccharide (LPS), in Mice

Background/Objective:

Lipopolysaccharides (LPS) promote allergic responses to nickel (Ni) both in the sensitization and elicitation steps. In this study, we examine the effect of pre-sensitization to LPS on the occurrence of Ni allergy using a mouse model.

Method:

A 100 mg of LPS was injected into C57BL/6J mice intraperitoneally (ip). Three weeks later, the mice were subsequently injected with 0.3 μ moles of nickel dichloride (NiCl₂) and 100 μg of CpG-DNA, which acted as an adjuvant. The mice were repeatedly immunized with the 0.3 μg of nickel sulfate (NiSO₄), along with 300 μl of the adjuvant, Inject Alum (Pierce, USA). Then we examined the producing capabilities of T helper type 1 (Th1) and 2 (Th2) cytokines (interferon-gamma- (IFN)-γ and interleukin (IL)-10, respectively) from anti CD3 antibody-stimulated spleen cells.

Results:

Pre-treatment with LPS, followed by repeated challenges with Ni²⁺ and adjuvants significantly enhanced the IFN-γ-producing capability of spleen cells (n=5, p<0.01); however, that could not enhance the capability of spleen cells by a single challenge with Ni²⁺ and adjuvants (n=5). In contrast, without LPS treatment, single or even repeated challenges by Ni²⁺ could not enhance the IFN-γ-producing capability. On the other hand, the IL-10-producing capability of spleen cells was not enhanced even by LPS and repeated challenges with Ni²⁺ and adjuvants.

Conclusion:

The solitary pre-sensitization to LPS is essential for the onset of Ni allergy by shifting the Th1/Th2 immune balance toward a Th1 dominant.

Allergy-Inducing Chromium Compounds Trigger Potent Innate Immune Stimulation Via ROS-Dependent Inflammasome Activation

Chromium allergy is a common occupational skin disease mediated by chromium (VI)-specific T cells that induce delayed-type hypersensitivity in sensitized individuals. Additionally, chromium (VI) can act as an irritant. Both responses critically require innate immune activation, but if and how chromium (VI) elicits this signal is currently unclear. Using human monocytes, primary human keratinocytes, and murine dendritic cells we show that chromium (VI) compounds fail to trigger direct proinflammatory activation but potently induce processing and secretion of IL-1β. IL-1β release required priming by phorbol-ester or toll-like receptor stimulation and was prevented by inhibition of K⁺ efflux, NLRP3 depletion or caspase-1 inhibition, identifying chromium (VI) as a hapten activator of the NLRP3 inflammasome. Inflammasome activation was initiated by mitochondrial reactive oxygen species production triggered by chromium (VI), as indicated by sensitivity to treatment with the ROS scavenger N-acetyl cysteine and a coinciding failure of K⁺ efflux, caspase-1, or NLRP3 inhibition to prevent mitochondrial reactive oxygen species accumulation. IL-1β release further correlated with cytotoxicity that was secondary to reactive oxygen species, K⁺ efflux, and NLRP3 activation. Trivalent chromium was unable to induce mitochondrial reactive oxygen species production, inflammasome activation, and cytotoxicity, suggesting that oxidation state-specific differences in mitochondrial reactivity may determine inflammasome activation and allergic/irritant capacity of different chromium compounds.

Metal nanoparticles in the presence of lipopolysaccharides trigger the onset of metal allergy in mice

Many people suffer from metal allergy, and the recently demonstrated presence of naturally occurring metal nanoparticles in our environment could present a new candidate for inducing metal allergy. Here, we show that mice pretreated with silver nanoparticles (nAg) and lipopolysaccharides, but not with the silver ions that are thought to cause allergies, developed allergic inflammation in response to the silver. nAg-induced acquired immune responses depended on CD4(+) T cells and elicited IL-17A-mediated inflammation, similar to that observed in human metal allergy. Nickel nanoparticles also caused sensitization in the mice, whereas gold and silica nanoparticles, which are minimally ionizable, did not. Quantitative analysis of the silver distribution suggested that small nAg (≤10 nm) transferred to the draining lymph node and released ions more readily than large nAg (>10 nm). These results suggest that metal nanoparticles served as ion carriers to enable metal sensitization. Our data demonstrate a potentially new trigger for metal allergy.

Evidence and conjecture about mechanisms of cutaneous disease in photodermatology

Photosensitivity disorders are caused by a variety of mechanisms. Three common themes are as follows: excess chromophore allowing visible light energy to cause photodynamic damage, reduced DNA repair capacity to UV-induced DNA damage, and enhanced sensitivity to light-induced allergens mediated immunologically. Although the cause of each condition may be known, the precise pathogenesis underlying the photosensitivity has taken longer to understand. By focussing on three clinical disorders under each of these themes, we have explored the following: why erythropoietic protoporphyria differs so markedly from the other cutaneous porphyrias; how a DNA repair defect was eventually revealed to be the underlying cause of the vitamin B3 deficiency disorder of pellagra; an immunological explanation for the over reactivity to photoallergens in chronic actinic dermatitis.

The antihistamine olopatadine regulates T cell activation in palladium allergy

Because of its corrosion resistance palladium (Pd) has been widely used in many consumer products ranging from fashion accessories to dental materials. Recently, however, an increase in Pd allergy cases has been reported. Metal allergy is categorized as a Type IV allergy, which is characterized as a delayed-type hypersensitivity reaction in which T cells are known to play an important role; however, the precise mechanism of their action remains unclear. Here we defined the relationship between histamine and the Pd allergic reaction specifically with respect to T cell responses. To verify the effects of histamine on T cells, we examined whether there is a change in IFN-γ production following stimulation of histamine or the antihistamine, olopatadine hydrochloride (OLP), in vitro. In addition, we assessed whether OLP administration affected the degree of footpad swelling or IFN-γ production during the Pd allergy response in mice. We found that histamine stimulation increased IFN-γ production in T cells, specifically enhancing IFN-γ production in CD8(+) T cells compared with CD4(+) T cells. Interestingly, OLP suppressed the production of IFN-γ in CD8(+) T cells, and this compound inhibited footpad swelling and IFN-γ production in mice with Pd allergy. These results suggest that histamine promotes the Type IV allergic reaction and thus, the histamine 1 receptor (H1R) might be useful therapeutic target for treatment of metal allergy.

Mast cell histamine-mediated transient inflammation following exposure to nickel promotes nickel allergy in mice

We previously reported that allergic responses to nickel (Ni) were minimal in mice deficient in the histamine-forming enzyme histidine decarboxylase (HDC-KO), suggesting an involvement of histamine in allergic responses to Ni. However, it remains unclear how histamine is involved in the process of Ni allergy. Here, we examined the role of histamine in Ni allergy using a murine model previously established by us. Mice were sensitized to Ni by intraperitoneal injection of a NiCl2 -lipopolysaccharide (LPS) mixture. Ten days later, allergic inflammation was elicited by challenging ear-pinnas intradermally with NiCl2 . Then, ear-swelling was measured. Pyrilamine (histamine H1-receptor antagonist) or cromoglicate (mast cell stabilizer) was intravenously injected 1 h before the sensitization or the challenge. In cell-transfer experiments, spleen cells from Ni-sensitized donor mice were intravenously transferred into non-sensitized recipient mice. In both sensitized and non-sensitized mice, 1 mm or more NiCl2 (injected into ear-pinnas) induced transient non-allergic inflammation (Ni-TI) with accompanying mast cell degranulation. LPS did not affect the magnitude of this Ni-TI. Pyrilamine and cromoglicate reduced either the Ni-TI or the ensuing allergic inflammation when administered before Ni-TI (at either the sensitization or elicitation step), but not if administered when the Ni-TI had subsided. Experiments on HDC-KO and H1-receptor-KO mice, and also cell-transfer experiments using these mice, demonstrated histamine's involvement in both the sensitization and elicitation steps. These results suggest that mast cell histamine-mediated Ni-TI promotes subsequent allergic inflammatory responses to Ni, raising the possibility that control of Ni-TI by drugs may be effective at preventing or reducing Ni allergy.

Molecular Mechanisms of Nickel Allergy

Allergic contact hypersensitivity to metals is a delayed-type allergy. Although various metals are known to produce an allergic reaction, nickel is the most frequent cause of metal allergy. Researchers have attempted to elucidate the mechanisms of metal allergy using animal models and human patients. Here, the immunological and molecular mechanisms of metal allergy are described based on the findings of previous studies, including those that were recently published. In addition, the adsorption and excretion of various metals, in particular nickel, is discussed to further understand the pathogenesis of metal allergy.

Possible Immune Regulation of Natural Killer T Cells in a Murine Model of Metal Ion-Induced Allergic Contact Dermatitis

Metal often causes delayed-type hypersensitivity reactions, which are possibly mediated by accumulating T cells in the inflamed skin, called irritant or allergic contact dermatitis. However, accumulating T cells during development of a metal allergy are poorly characterized because a suitable animal model is unavailable. We have previously established novel murine models of metal allergy and found accumulation of both metal-specific T cells and natural killer (NK) T cells in the inflamed skin. In our novel models of metal allergy, skin hypersensitivity responses were induced through repeated sensitizations by administration of metal chloride and lipopolysaccharide into the mouse groin followed by metal chloride challenge in the footpad. These models enabled us to investigate the precise mechanisms of the immune responses of metal allergy in the inflamed skin. In this review, we summarize the immune responses in several murine models of metal allergy and describe which antigen-specific responses occur in the inflamed skin during allergic contact dermatitis in terms of the T cell receptor. In addition, we consider the immune regulation of accumulated NK T cells in metal ion-induced allergic contact dermatitis.

Methods to Investigate the Role of Toll-Like Receptors in Allergic Contact Dermatitis

Allergic contact disease is a common inflammatory skin disease resulting from hyperresponsiveness to harmless nonprotein substances such as metals, fragrances, or rubber. Recent research has highlighted a prominent role of Toll-like receptors, particularly TLR4 in contact allergen-induced innate immune activation that crucially contributes to the pathogenesis of this disease. Here we describe several methods to investigate the role of Toll-like receptors in contact allergen-induced pro-inflammatory responses. These include expansion of disease-relevant human primary cells including endothelial cells and keratinocytes and their manipulation of TLR signaling by transfection, retroviral infection and RNA interference, basic methods to induce contact hypersensitivity in mice, and protocols for adoptive transfer of hapten-stimulated dendritic cells and T cells from TLR-deficient mice to wild-type mice and vice versa wild-type mice to TLR-deficient mice in order to explore cell-specific roles of TLRs in contact hypersensitivity responses.

Immunology of metal allergies

Allergic contact hypersensitivity to metal allergens is a common health concern worldwide, greatly impacting affected individuals with regard to both quality of life and their ability to work. With an estimated 15-20 % of the Western population hypersensitive to at least one metal allergen, sensitization rates for metallic haptens by far outnumber those reported for other common triggers of allergic contact dermatitis such as fragrances and rubber. Unfortunately, the prevalence of metal-induced hypersensitivity remains high despite extensive legislative efforts to ban/reduce the content of allergy-causing metals in recreational and occupational products. Recently, much progress has been made regarding the perception mechanisms underlying the inflammatory responses to this unique group of contact allergens. This review summarizes recent advances in our understanding of this enigmatic disease. Particular emphasis is put on the mechanisms of innate immune activation and T cell activation by common metal allergens such as nickel, cobalt, palladium, and chromate.

Regulation of immunological and inflammatory functions by biotin

Biotin is a water-soluble B-complex vitamin and is well-known as a co-factor for 5 indispensable carboxylases. Holocarboxylase synthetase (HLCS) catalyzes the biotinylation of carboxylases and other proteins, whereas biotinidase catalyzes the release of biotin from biotinylated peptides. Previous studies have reported that nutritional biotin deficiency and genetic defects in either HLCS or biotinidase induces cutaneous inflammation and immunological disorders. Since biotin-dependent carboxylases involve various cellular metabolic pathways including gluconeogenesis, fatty acid synthesis, and the metabolism of branched-chain amino acids and odd-chain fatty acids, metabolic abnormalities may play important roles in immunological and inflammatory disorders caused by biotin deficiency. Transcriptional factors, including NF-κB and Sp1/3, are also affected by the status of biotin, indicating that biotin regulates immunological and inflammatory functions independently of biotin-dependent carboxylases. An in-vivo analysis with a murine model revealed the therapeutic effects of biotin supplementation on metal allergies. The novel roles of biotinylated proteins and their related enzymes have recently been reported. Non-carboxylase biotinylated proteins induce chemokine production. HLCS is a nuclear protein involved in epigenetic and chromatin regulation. In this review, comprehensive knowledge on the regulation of immunological and inflammatory functions by biotin and its potential as a therapeutic agent is discussed.

Nickel ions selectively inhibit lipopolysaccharide-induced interleukin-6 production by decreasing its mRNA stability

Nickel (Ni) ions easily elute from many alloys and elicit inflammation and allergies. Previous studies have shown that infections due to the implantation of medical devices cause inflammation and enhance the elution of Ni ions (Ni²⁺). However, cross-talk between infection- and Ni²⁺-induced signaling pathways has not yet been elucidated in detail. In the present study, we investigated the effects of Ni2+ on the lipopolysaccharide (LPS)-induced production of cytokines in a LPS-induced air pouch-type inflammation model in BALB/c mice and the murine macrophage cell line RAW264. We demonstrated that Ni²⁺ inhibited the LPS-induced production of interleukin (IL)-6, but not that of tumor necrosis factor (TNF)-α both in vivo and in vitro. This inhibitory effect was also observed with cobalt ion (Co²⁺), but not with chloride ion (Cl⁻), zinc ion (Zn²⁺), or palladium ion (Pd²⁺), and was highly selective to the production of IL-6. Ni²⁺ did not inhibit the activation of ERK1/2, p38 MAPK, or JNK. Although Ni²⁺ decreased IL-6 mRNA levels, it failed to inhibit the LPS-induced activation of the IL-6 promoter. An experiment using actinomycin D, a transcription inhibitor, revealed that Ni²⁺ decreased the stability of IL-6 mRNA. Moreover, Ni²⁺ inhibited the LPS-induced expression of Arid5a, but not regnase-1. These results demonstrated that Ni²⁺ may have selectively inhibited the LPS-induced production of IL-6 by decreasing the Arid5a-dependent stabilization of IL-6 mRNA.

Resin monomers act as adjuvants in Ni-induced allergic dermatitis in vivo

Resin monomers (RMs) are inflammatory agents and are thought to cause allergic contact dermatitis (ACD). However, mouse models are lacking, possibly because of the weak antigenicities of RMs. We previously reported that inflammatory substances can promote the allergic dermatitis (AD) induced by intradermally injected nickel (Ni-AD) in mice. Here, we examined the effects of RMs on Ni-AD. To sensitize mice to Ni, a mixture containing non-toxic concentrations of NiCl2 and an RM [either methyl methacrylate (MMA) or 2-hydroxyethyl methacrylate (HEMA)] was injected intraperitoneally or into ear-pinnae intradermally. Ten days later, a mixture containing various concentrations of NiCl2 and/or an RM was intradermally injected into ear-pinnae, and ear-swelling was measured. In adoptive transfer experiments, spleen cells from sensitized mice were transferred intravenously into non-sensitized recipients, and 24 h later NiCl2 was challenged to ear-pinnae. Whether injected intraperitoneally or intradermally, RM plus NiCl2 mixtures were effective in sensitizing mice to Ni. AD-inducing Ni concentrations were greatly reduced in the presence of MMA or HEMA (at the sensitization step from 10 mM to 5 or 50 µM, respectively, and at the elicitation step from 10 µM to 10 or 100 nM, respectively). These effects of RMs were weaker in IL-1-knockout mice and in macrophage-depleted mice. Cell-transfer experiments in IL-1-knockout mice indicated that both the sensitization and elicitation steps depended on IL-1. Challenge with an RM alone did not induce allergic ear-swelling in mice given the same RM + NiCl2 10 days before the challenge. These results suggest that RMs act as adjuvants, not as antigens, to promote Ni-AD by reducing the AD-inducing concentration of Ni, and that IL-1 and macrophages are critically important for the adjuvant effects. We speculate that what were previously thought of as "RM-ACD" might include ACD caused by antigens other than RMs that have undergone promotion by the adjuvant effects of RMs.

A critical role for thymic stromal lymphopoietin in nickel-induced allergy in mice

Ni is the most frequent cause of contact allergy induced by metals. However, the underlying mechanism of this induction is unknown. Our previous research demonstrates that activation of dendritic cells (DCs) through p38MAPK/MKK6 is required for Ni-induced allergy in mice. In the current study, we investigated the cellular and molecular mechanisms underlying Ni-induced allergy using a mouse model that involves injecting Ni into the ear, with or without Freund's incomplete or complete adjuvants. Nickel had greater potential to cause allergic reactions compared with palladium and gold. Among the proteins expressed at higher levels in mice with Ni-induced allergy, we focused on thymic stromal lymphopoietin (TSLP), which is produced in abundance by keratinocytes. We detected increased expression of the TSLP receptor (TSLPR) in DCs from cervical lymph nodes of mice with Ni-induced allergy, suggesting that DCs in ear tissues were activated through TSLPR signaling induced by keratinocyte-derived TSLP. Furthermore, delayed-type hypersensitivity reactions in mice with Ni-induced allergy were decreased significantly by injection of a Tslp-short interfering RNA along with atelocollagen in the ear skin. These results suggest that Ni allergy may be triggered by a TSLP/TSLPR-mediated interaction between epithelial and immune cells.

NKG2D⁺ IFN-γ⁺ CD8⁺ T cells are responsible for palladium allergy

Nickel, cobalt, and chromium are well known to be causal agents of allergic contact dermatitis. Palladium (Pd) can also cause allergic disease and exposure results from wide use of this metal in dental restorations and jewelry. Metal allergy is categorized as a delayed-type hypersensitivity, and metal-responsive T cell clones have been isolated from allergic patients. However, compared to nickel, little is known about the pathology of allergic disease mediated by Pd, and pathogenic T cells are poorly understood. To identify the pathogenic T cells that are responsible for onset of Pd allergy, we enriched metal-responsive lymphocytes by sequential adoptive transfer of involved lymph node cells. Here we show that sequential adoptive transfer gradually increased the incidence and the intensity of Pd allergy, and CD8⁺ T cells are responsible for the disease as CD8⁺ T cell-depleted mice and β2-microglobulin-deficient mice did not develop Pd allergy. In addition, we found that draining lymph node cells skewed toward CD8⁺ T cells in response to Pd challenge in 8th adoptive transferred recipient mice. The CD8⁺ T cells expressed NKG2D, a costimulatory molecule involved in the production of IFN-γ. NKG2D ligand was also induced in Pd-injected tissues. Furthermore, both NKG2D ligand-transgenic mice, where NKG2D is downmodulated, and IFN-γ-deficient mice showed impaired Pd allergy. Taken together, these results indicate that IFN-γ-producing NKG2D⁺ CD8⁺ T cells are responsible for Pd allergy and suggest that NKG2D is a potential therapeutic target for treatment of metal allergy.

Accumulation of metal-specific T cells in inflamed skin in a novel murine model of chromium-induced allergic contact dermatitis

Chromium (Cr) causes delayed-type hypersensitivity reactions possibly mediated by accumulating T cells into allergic inflamed skin, which are called irritants or allergic contact dermatitis. However, accumulating T cells during development of metal allergy are poorly characterized because a suitable animal model is not available. This study aimed to elucidate the skewing of T-cell receptor (TCR) repertoire and cytokine profiles in accumulated T cells in inflamed skin during elucidation of Cr allergy. A novel model of Cr allergy was induced by two sensitizations of Cr plus lipopolysaccharide solution into mouse groin followed by single Cr challenge into the footpad. TCR repertoires and nucleotide sequences of complementary determining region 3 were assessed in accumulated T cells from inflamed skin. Cytokine expression profiles and T-cell phenotypes were determined by qPCR. CD3+CD4+ T cells accumulated in allergic footpads and produced increased T helper 1 (Th1) type cytokines, Fas, and Fas ligand in the footpads after challenge, suggesting CD4+ Th1 cells locally expanded in response to Cr. Accumulated T cells included natural killer (NK) T cells and Cr-specific T cells with VA11-1/VB14-1 usage, suggesting metal-specific T cells driven by invariant NKT cells might contribute to the pathogenesis of Cr allergy.

Characterization of T cell receptors of Th1 cells infiltrating inflamed skin of a novel murine model of palladium-induced metal allergy

Metal allergy is categorized as a delayed-type hypersensitivity reaction, and is characterized by the recruitment of lymphocytes into sites of allergic inflammation. Because of the unavailability of suitable animal models for metal allergy, the role of T cells in the pathogenesis of metal allergy has not been explored. Thus, we developed a novel mouse model for metal allergy associated with infiltration of T cells by multiple injections of palladium (Pd) plus lipopolysaccharide into the footpad. Using this model, we characterized footpad-infiltrating T cells in terms of phenotypic markers, T cell receptor (TCR) repertoires and cytokine expression. CD3+ CD4+ T cells accumulated in the allergic footpads 7 days after Pd challenge. The expression levels of CD25, interleukin-2, interferon-γ and tumor necrosis factor, but not interleukin-4 and interleukin-5, increased in the footpads after challenge, suggesting CD4+ T helper 1 (Th1) cells locally expanded in response to Pd. Infiltrated T cells in the footpads frequently expressed AV18-1 and BV8-2 T cell receptor (TCR) chains compared with T cells in the lymph nodes and exhibited oligoclonality. T-cell clones identified from Pd-allergic mouse footpads shared identical CDR3 sequences containing AV18-1 and BV8-2. These results suggest that TCR AV18-1 and BV8-2 play dominant and critical parts in the antigen specificity of Pd-specific Th1 cells.