Contact Hypersensitivity Response Research Articles

Hypotensive drugs mitigate the high-sodium diet-induced pro-inflammatory activation of mouse macrophages in vivo

Nowadays, there is an increasing emphasis on the need to alleviate the chronic inflammatory response to effectively treat hypertension. However, there are still gaps in our understanding on how to achieve this. Therefore, research on interaction of antihypertensive drugs with the immune system is extremely interesting, since their therapeutic effect could partly result from amelioration of hypertension-related inflammation, in which macrophages seem to play a pivotal role. Thus, current comprehensive studies have investigated the impact of repeatedly administered hypotensive drugs (captopril, olmesartan, propranolol, carvedilol, amlodipine, verapamil) on macrophage functions in the innate and adaptive immunity, as well as if drug-induced effects are affected by a high-sodium diet (HSD), one of the key environmental risk factors of hypertension. Although the assayed medications increased the generation of reactive oxygen and nitrogen intermediates by macrophages from standard fed donors, they reversed HSD-induced enhancing effects on macrophage oxidative burst and secretion of pro-inflammatory cytokines. On the other hand, some drugs increased macrophage phagocytic activity and the expression of surface markers involved in antigen presentation, which translated into enhanced macrophage ability to activate B cells for antibody production. Moreover, the assayed medications augmented macrophage function and the effector phase of contact hypersensitivity reaction, but suppressed the sensitization phase of cell-mediated hypersensitivity under HSD conditions. Our current findings contribute to the recognition of mechanisms, by which excessive sodium intake affects macrophage immune activity in hypertensive individuals, and provide evidence that the assayed medications mitigate most of the HSD-induced adverse effects, suggesting their additional protective therapeutic activity.

Allergic contact dermatitis caused by topical corticosteroids: A review for clinicoepidemiological presentation, evaluation, and management aspects

Dermatitis medicamentosa or contact dermatitis to topically applied medicaments, active ingredients or excipients, is encountered frequently in clinical practice and should be suspected in patients showing resistance to treatment despite adequate therapy and in patients, who complain of intolerance to a particular treatment. Topical corticosteroids are prescribed mostly in dermatology for their anti-inflammatory, antiproliferative, and immunosuppressive actions to treat various inflammatory dermatoses. These may act as allergens and produce immunoglobulin E-mediated immediate hypersensitivity (anaphylaxis, urticaria, angioedema, bronchospasm, vomiting, and cardiovascular collapse) or T-cell-mediated allergic contact dermatitis (ACD). Although it occurs less often and is not life threatening, ACD negatively impacts the quality of life by worsening preexisting dermatitis. The prevalence of hypersensitivity to these allergens varies across regions and periods of time depending on the clinical practice, prescribing habits, and types of cases studied. Over-the-counter availability of corticosteroids in multiple formulations in recent years may further compound the problem due to their indiscriminate and extensive use. Although about one-third of all cases of contact dermatitis are initiated or perpetuated by topical medicaments, the occurrence of contact dermatitis due to corticosteroids remains undersuspected. This is perhaps due to their anti-inflammatory and immunosuppressive properties that make it difficult to doubt and prove contact sensitivity that may be from a corticosteroid itself or to the additives and vehicles in the formulation. Patch testing can help identify the culprit agents in ACD but early diagnosis depends on clinical suspicion. Sensitization in contact dermatitis exhibits cross-reactivity patterns based on corticosteroid structure. Clinicoepidemiological presentation, evaluation, and management aspects of contact hypersensitivity reactions to corticosteroids are reviewed.

Tolerogenic phenotype of dendritic cells is induced after hapten sensitization followed by attenuated contact hypersensitivity response in atopic dermatitis model NC/Nga mice

Allergic contact dermatitis (ACD) and atopic dermatitis (AD) are common inflammatory diseases. We previously reported attenuated contact hypersensitivity (CHS) responses in AD model mice using 2,4-dinitrofluorobenzene, reflecting clinical experiments. However, previous studies have not addressed the commonality of findings across haptens and mechanisms focused on dendritic cells (DCs). Thus, this study evaluated CHS responses to fluorescein isothiocyanate (FITC) and DC migration and maturation in the sensitization phase of CHS in AD. CHS responses to FITC were compared between NC/Nga mice without and with AD induction (non-AD and AD mice, respectively). T-cell responses and DC migration and maturation after FITC-induced sensitization were examined in the draining lymph nodes of non-AD and AD mice. AD mice demonstrated reduced CHS responses to FITC under decreased T-cell proliferation following sensitization and interferon-γ production by hapten-specific T cells compared with non-AD mice. In addition, the number of FITC+CD11c+MHC class IIhigh migratory DCs 24 h after FITC sensitization was comparable between non-AD and AD mice. However, FITC+CD11c+MHC class IIhigh migratory DCs in AD mice exhibited lower expression levels of CD80 and CD86 and higher expression levels of PD-L1 and mRNA of transforming growth factor beta than non-AD mice. These findings suggest that attenuated CHS responses may be hapten-independent and the induction of the tolerogenic phenotype of hapten-bearing DCs can contribute to reduced T-cell proliferation after sensitization and CHS responses in AD.

Natural killer cell-mediated contact dermatitis-like reaction induced by treatment with TLR3 ligand poly(I:C).

Poly(I:C) is recognised by endosomal Toll-like receptor 3 (TLR3) and activates cytotoxic CD8(+) lymphocytes and natural killer (NK) cells. It has been shown that the viral TLR3 agonist induces robust and long-lasting T-cell-mediated responses. In addition, TLR3 modulates the contact hypersensitivity reaction. This study aimed to determine whether poly(I:C) injection can induce NK-mediated hapten reactivity in mice. Mice were treated with poly(I:C), and their response to dinitrofluorobenzene hapten was measured by assessing ear swelling and serum interferon gamma (IFN-γ) production. Adoptive cell transfer and cell sorting were used to investigate the mechanism of the reaction, and the phenotype of poly(I:C)-activated liver NK cells was determined by flow cytometry analysis. The results showed that poly(I:C) administration increased ear swelling, serum IFN-γ levels and the response to hapten in both immunocompetent and T- and B-cell-deficient mice. Only liver poly(I:C)-activated DX5(+) NK cells were able to transfer reactivity to hapten into a naive recipient. Induction of liver NK cells after poly(I:C) administration was TLR3/TRIF- and IFN-γ-dependent, interleukin 12-independent, and not modulated by MyD88. This study provides new insights into how poly(I:C) stimulates NK-mediated reactivity to hapten and suggests that liver NK cells may modulate the immune response to non-pathogenic factors during viral infection.

Epicutaneous immunization with TNP-Ig antigen induces CD11c+IL-10+ dendritic cells that promote suppression of Th1-mediated contact hypersensitivity in humanized HLA-DR4 transgenic mice

The contact hypersensitivity response (CHS) is a mouse model of allergic contact dermatitis in humans. The reaction is classified as type IV hypersensitivity and underlies many autoimmune disorders. Experiments employing the CHS model in wild-type mice showed that the protein antigen applied to the skin in the form of a gauze patch one week before the induction of Th1-dependent CHS was an effective strategy to reduce the inflammatory response in the skin. The approach of epicutaneous (EC) immunization also effectively suppressed the inflammatory response in various mouse models of autoimmune diseases. To evaluate the potential of EC immunization to suppress T cell-dependent immune response in humans, we used HLA-DR4 tg mice, which express the human DRB1*0401 allele and lack all endogenous mouse MHC class II genes. Our data show that EC immunization with TNP-conjugated protein antigen followed by induction of CHS to trinitrochlorobenzene (TNCB), effectively suppressed the CHS response as described by ear swelling, MPO activity in ear extracts, and the number of TCRβ+CD4+IFN-γ+ CHS T-effector cells in auxiliary and inguinal lymph nodes (ALN) and spleen (SPL) of HLA-DR4 tg mice. EC-induced suppression increases the frequency of CD11c+IL-10+ DCs in SPL. Their immunoregulatory role was confirmed by s.c. immunization with TNP-CD11c+DCs prior to CHS elicitation and induction. Our data in HLA-DR4 tg mice show that EC protein immunization induces IL-10-producing DCs, which suppress the development of CD4+IFN-γ+ T cell-dependent CHS, implying that EC protein immunization could be of therapeutic importance for T cell-mediated diseases in humans.

CTLA-4 suppresses hapten-induced contact hypersensitivity in atopic dermatitis model mice

Atopic dermatitis (AD) patients with skin barrier dysfunction are considered to be at a higher risk of allergic contact dermatitis (ACD), although previous studies showed that attenuated ACD responses to strong sensitizers in AD patients compared to healthy controls. However, the mechanisms of ACD response attenuation in AD patients are unclear. Therefore, using the contact hypersensitivity (CHS) mouse model, this study explored the differences in CHS responses to hapten sensitization between NC/Nga mice with or without AD induction (i.e., non-AD and AD mice, respectively). In this study, ear swelling and hapten-specific T cell proliferation were significantly lower in AD than in non-AD mice. Moreover, we examined the T cells expressing cytotoxic T lymphocyte antigen-4 (CTLA-4), which is known to suppress T cell activation, and found a higher frequency of CTLA-4+ regulatory T cells in draining lymph node cells in AD than in non-AD mice. Furthermore, the blockade of CTLA-4 using a monoclonal antibody eliminated the difference in ear swelling between non-AD and AD mice. These findings suggested that CTLA-4+T cells may contribute to suppressing the CHS responses in AD mice.

TLR4 dependent generation of a novel bone marrow-derived inflammatory monocyte population required for elicitation of skin contact hypersensitivity responses

Abstract Contact hypersensitivity (CHS) is a CD8 T cell mediated response to hapten skin sensitization and challenge. Hapten-primed CD8 cell infiltration into the skin challenge site during elicitation of CHS requires prior infiltration and activation of a novel population of Gr-1 +CXCR2 +cells expressing FasL and perforin. The goal of these studies was to further characterize this novel population of myeloid-derived cells and to determine mechanisms generating the cells in the bone marrow during elicitation of CHS. The myeloid cells were purified from the bone marrow of hapten sensitized mice 2 hrs after hapten challenge by depletion of CD3 +, B220 +, NK1 +, F4/80 +, class II MHC +and Ly6G +cells. Flow cytometry analyses indicate >90% of the remaining bone marrow cells were CD11c +, Ly6C +, CCR2 +, expressing FasL +and perforin. This cell population was at low numbers in the bone marrow of naïve mice but increased to peak numbers 2 hrs. after hapten challenge of sensitized WT and Rag −/−mice and T-cell depleted WT mice. Generation of the myeloid cells was absent in hapten sensitized and challenged TLR4-deficient mice and was inhibited by treatment with anti-TNFa mAb at the time of hapten challenge. Whereas generation of neutrophils is inhibited by anti-G-CSF antibody, this treatment further increased numbers of these myeloid cells in the bone marrow following hapten challenge. These results indicate that generation of bone marrow-derived Ly6C +CXCR2 +cells expressing FasL and perforin in response to inflammation requires TNFa and TLR4 signaling that occurs independently of T cell activation.

052 Adenosine production in the ear is necessary to limit contact hypersensitivity reaction induced by neutrophil

052 Adenosine production in the ear is necessary to limit contact hypersensitivity reaction induced by neutrophil

Erratum: Contact Hypersensitivity as a Murine Model of Allergic Contact Dermatitis.

CHS = contact hypersensitivity reaction; TNCB = 2,4,6-trinitrochlorobenzene. Please click here to view a larger version of this figure. to: Figure 1: Induction of CHS. Sensitization, challenge, and ear measurement. CHS = contact hypersensitivity reaction; TNCB = 2,4,6-trinitrochlorobenzene. Please click here to view a larger version of this figure. Figure 2 of the Representative Results has been updated from: Figure 2: Adoptive transfer of the CHS-effector cells. ALNs =axillary and inguinal lymph nodes; CHS = contact hypersensitivity reaction; i.v. = intravenously; SPLs = spleens; TNCB = 2,4,6-trinitrochlorobenzene. Please click here to view a larger version of this figure. to: Figure 2: Adoptive transfer of the CHS-effector cells. ALNs =axillary and inguinal lymph nodes; CHS = contact hypersensitivity reaction; i.v. = intravenously; SPLs = spleens; TNCB = 2,4,6-trinitrochlorobenzene. Please click here to view a larger version of this figure.

Severe Hypersensitivity Reaction to Dermabond Prineo After Anterior Cervical Discectomy and Fusion: A Case Report.

A 68-year-old woman underwent an anterior cervical discectomy and fusion for cervical radiculopathy and subsequently developed a severe contact hypersensitivity reaction in response to Dermabond Prineo, beginning 10 days postoperatively. The Dermabond Prineo mesh was removed, and the patient was treated symptomatically with diphenhydramine, systemic steroids, and oral antibiotics, with complete resolution of her symptoms. This is the first reported contact hypersensitivity reaction to Dermabond Prineo in the context of spine surgery. Surgeons should be able to recognize this presentation and treat this appropriately.

Tolerance to 2,4-Dinitrofluorobenzene‒Induced Contact Hypersensitivity Is Mediated by CD73-Expressing Tissue-Homing Regulatory T Cells

Regulatory T cells (Tregs) express CD73, an ectonucleotidase that converts adenosine (Ado) monophosphate to Ado, which has been shown to suppress immune reactions. To investigate the role(s) of CD73+ Tregs during the induction of tolerance, we used a 2,4-dinitrofluorobenzene‒driven contact hypersensitivity model, in which tolerance can be induced by pretreating wild type mice with 2,4-dinitrothiocyanobenzene. CD73-deficient mice were unable to acquire tolerance. Likewise, transfer of CD73‒/‒ Tregs failed to suppress 2,4-dinitrofluorobenzene‒induced ear swelling in wild type mice, whereas transfer of wild type‒derived Tregs into CD73‒/‒ mice re-established tolerance. This indicates a crucial role of CD73+ Tregs for skin-induced tolerance. Furthermore, we found that 2,4-dinitrothiocyanobenzene induces more activated CD73+ tissue-homing Tregs (marked by Ki-67, CTLA4, CCR4, CD103, CCR6, and CD49b expression) in draining lymph nodes and blood, eventually accumulating in the skin. The application of anti-CD73 antibodies that block CD73-derived Ado production as well as the injection of Ado deaminase, which degrades Ado in tissues, abrogated tolerance induction. Thus, our data indicate that CD73+ Ado-producing Tregs are crucial for the regulation of contact hypersensitivity reactions and tolerance induction in the skin and that manipulating the function(s) of CD73 in tissues may offer a tool to influence autoimmunity and inflammation invivo.

Oral Cadmium Intake Enhances Contact Allergen-induced Skin Reaction in Rats

ObjectiveThe effect of oral cadmium (Cd) intake to influence contact skin allergies was examined, since it is known that Cd is a heavy metal that affects many tissues, including the skin, in which it disturbs homeostasis, thus resulting in inflammation and injury. MethodsMale rats were evoked with experimental contact hypersensitivity reaction (CHS) to hapten dinitrochlorobenzene (DNCB), after prolonged (30 day) oral exposure to an environmentally relevant Cd dose (5 ppm). The ear cell population was analyzed with flow cytometry. Cytokine production by ear skin cells and the activity of skin-draining lymph node (DLN) cells were measured using enzyme-linked immunosorbent assay (ELISA). ResultsOrally acquired Cd (5 ppm) increased CHS intensity only in Dark Agouti (DA) rats by affecting inflammatory responses in both the sensitization (an increase of IFN-γ and IL-17 cytokine production) and challenge (an increase of CD8+ and CD4+ cell number and TNF, IFN-γ and IL-17 cytokine production) phases. An increased CHS reaction was seen in Albino Oxford (AO) rats only at a high Cd dose (50 ppm), during the challenge phase (an increase of CD8+ and CD4+ cell number and TNF, IFN-γ and IL-17 cytokine production). ConclusionThese novel data indicate that oral Cd intensifies the skin response to sensitizing chemicals such as DNCB.

IKKβ increases neuropilin-2 and promotes the inhibitory function of CD9+ Bregs to control allergic diseases

Regulatory B cells (Bregs) potently suppress immune disorders, including allergic contact hypersensitivity (CHS). IKKβ overactivation is prominent in various inflammatory diseases. However, its effect on Bregs has not been defined. This study is to investigate the new regulator and inhibitory mechanism of Bregs. IkkβC46A transgenic mice with a Cys46 mutation, resulting in increased IKKβ activation, were employed for analysis. IL-10-competent CD9+ Bregs were expanded in IkkβC46A mice and B cell specific-IkkβC46A mutation mice. IkkβC46A mutant CD9+ Bregs had stronger suppressive effects on CD4+ and CD8+ T cells in vitro and CHS responses in vivo. The inhibitory CD9+ Bregs from IkkβC46A mice were characterized by upregulated Neuropilin 2 (Nrp2) and IL-10 in comparison with that of Ikkβwt mice. Interestingly, increased expression of Nrp2 was observed in CD9+ Bregs compared with that of CD9- B cells in wild-type mice. The suppressive activity of wild-type CD9+ Bregs in vitro was attenuated by inhibition of Nrp2 on Bregs or silencing its ligand Sema3f on CD4+ T cells. Our findings delineate a distinct role of IKKβ activation in enhancing Bregs to disturb the immune balance. It identifies Nrp2 as a novel regulatory molecule of Bregs that partly contributes to B cell-mediated immune tolerance.

Topical Application of Adenosine A2-Type Receptor Agonists Prevents Contact Hypersensitivity Reactions in Mice by Affecting Skin Dendritic Cells

Adenosine (Ado) produced by skin and skin migratory CD73+ dendritic cells is critically involved in tolerance tohaptens. We therefore investigated the use of Ado receptor agonists for the treatment of contact hypersensitivity reactions. A2A- 4-[2-[[6-Amino-9-(N-ethyl-β-D-ribofuranuronamidosyl)-9H-purin-2-yl]amino] ethyl]benzenepropanoic acid hydrochloride (CGS) and A2B- 2-[[6-Amino-3,5-dicyano-4-[4-[cyclopropylmethoxy]phenyl]-2-pyridinyl]thio]-acetamide (BAY) specific Ado receptor agonists were epicutaneously applied to the skin before sensitization and challenge with DNFB. Both agonists reduced ear swelling compared with solvent controls. This was accompanied by fewer activated T cells in the skin after the challenge and by higher numbers of T cells expressing anergic markers such as LAG-3, CD137, PD-1, CD272, and TIM-3 in the lymph nodes of CGS-treated groups. In ear tissue, Ado receptor agonist treatment reduced the production of proinflammatory cytokines and chemokines as well as the infiltration by neutrophils after sensitization. Moreover, reduced numbers of skin migratory dendritic cells producing less IL-12 and exhibiting lower expression of CD86 were recorded in lymph nodes after sensitization. In cocultures of skin migratory dendritic cells from CGS-treated mice with T cells, reduced proliferation of T cells and decreased secretion of proinflammatory cytokines compared with that of solvent controls were apparent. In conclusion, topical application of Ado receptor agonists to the skin prevents sensitization of T cells against haptens by reducing the migration and activation of skin migratory dendritic cells.

Contact Hypersensitivity as a Murine Model of Allergic Contact Dermatitis.

Contact hypersensitivity (CHS) is an experimental model of allergic contact dermatitis (ACD) that can be studied in mice. This study aims to present an objective laboratory method that may help to study the CHS reaction in mice, which can be measured and quantified by various tests. To induce CHS, on day "0", mice were sensitized on a previously shaved spot by abdominal skin painting with the hapten 2,4,6-trinitrochlorobenzene (TNCB) in an acetone-ethanol mixture, whereas negative control mice were sham sensitized with vehicle alone-acetone-ethanol mixture. On day "4", the baseline ear thickness was measured with a micrometer prior to the elicitation of CHS (challenge) by painting both ears with diluted TNCB both in the test and control groups. After 24 h, the ear swelling was measured with a micrometer. CHS is an example of a T cell-mediated immune response that causes swelling in inflamed tissue, peaking 24 h after the skin challenge with the same hapten. An increase in ear edema correlated with augmented ear weight, myeloperoxidase (MPO) activity, pro-inflammatory cytokine concentration in the ear extracts, increased thickening of the edematous dermis in the histological examination, and ear vascular permeability. There was also an increase in the concentration of TNP-specific IgG1 antibodies in the sera of the test group when compared with the control mice. Additionally, CHS can be successfully transferred with the CHS-effector cells obtained from donors previously sensitized with TNCB. The CHS-effector cells were administered intravenously into naïve recipient mice, which were subsequently challenged with the same diluted hapten. Ear swelling was measured with a micrometer 24 h later.

34232 Inhibition of tissue resident memory-T cells as a therapy for contact hypersensitivity

Background: Systemic therapy for eczema targets the immune system during active inflammation. Disease inevitably returns to previously inflamed but healed skin due to the persistence of tissue resident memory T (Trm) cells responding to autoantigens/allergens. The survival of Trm cells is regulated by IL-7 and IL-15. We present a mouse model of recurrent contact hypersensitivity (CHS) and suggest a novel approach to the treatment of inflammatory skin diseases through inhibition of Trm cells thereby establishing long-term disease remission. Methods: Mice were sensitized on the abdomen with the allergen 2,4-dinitrofluorobenzene (DNFB) (day −5). Mice were challenged on day 0 with DNFB, and then rechallenged on days 30 and 60. Ear swelling was measured every 12 hours for 96 hours postchallenge. Ear skin was harvested 2 days (inflamed skin) and 15 days (healed skin) after each DNFB ear challenge (days 32, 45, 62 and 75). Results: Serial DNFB challenges produced progressively stronger peak CHS responses (1-month vs. 2-months re-challenge; 8.8 vs. 12.0 μm, *P < .05). The number of Trm cells and expression of IL-15-receptor increased in healed skin compared with inflamed skin. There were increases in Trm cell numbers, and Trm expression of IL-7- and IL-15-receptor in skin at 2 months compared with 1-month DNFB rechallenge. Conclusions: Repeat CHS inflammation via serial DNFB challenge lead to accumulation of Trm cells expressing IL-7 and IL-15-receptors in healed skin. We suggest that inhibition of IL-7/IL-15-receptors during disease quiescence to reduce Trm cell numbers, may be a novel strategy to prevent dermatitis recurrence and maintain long-term remission.

Neutrophil extracellular traps are involved in enhanced contact hypersensitivity response in IL-36 receptor antagonist-deficient mice

Loss-of-function homozygous or compound heterozygous mutations in IL36RN, which encodes interleukin-36 receptor antagonist (IL-36Ra), have been implicated in the pathogenesis of skin disorders. We previously reported that Il36rn−/− mice exhibit an enhanced contact hypersensitivity (CHS) response through increased neutrophil recruitment. In addition, Il36rn−/− mice show severe imiquimod-induced psoriatic skin lesions and enhanced neutrophil extracellular trap (NET) formation. We hypothesized that NETs may play an important role in the CHS response. To confirm this, we examined the CHS response and NET formation in Il36rn−/− mice. Il36rn−/− mice showed enhanced CHS responses, increased infiltration of inflammatory cells, including neutrophils, CD4+ T cells, and CD8+ T cells, NET formation, and enhanced mRNA expression of cytokines and chemokines, including IL-1β, C-X-C motif chemokine ligand (CXCL)1, CXCL2, and IL-36γ. Furthermore, NET formation blockade improved the CHS response, which consequently decreased inflammatory cell infiltration and NET formation. Consistently, we observed decreased expression of these cytokines and chemokines. These findings indicate that IL-36Ra deficiency aggravates the CHS response caused by excessive inflammatory cell recruitment, NET formation, and cytokine and chemokine production, and that NET formation blockade alleviates the CHS response. Thus, NET formation may play a prominent role in the CHS response.

Hapten skin sensitization induces development of TLR4-dependent inflammatory monocytes that are required for elicitation of skin contact hypersensitivity responses αααα

Abstract Contact hypersensitivity (CHS) to skin sensitization and challenge with haptens is mediated by hapten-primed CD8 T cell populations producing IFN-γ and IL-17. Following hapten challenge these primed CD8 T cells induce hapten-presenting endothelial cells (EC) to produce CXCL1/CXCL2 directing the recruitment and activation of a population of inflammatory monocytes (IM) expressing Gr-1, Ly6C, CXCR2, CD11c, FasL and perforin that are required for hapten-primed CD8 T cell infiltration into the parenchymal skin tissue to mediate CHS. This study investigated mechanisms promoting development of these IM. The IM were absent in the bone marrow of hapten sensitized mice with defective IL-1, TNFα or TLR4 receptor signaling. Sensitized TLR4−/− mice lacked CHS responses to challenge despite equivalent numbers of hapten primed CD8 T cells producing IFNγ and IL-17 in skin-draining lymph nodes as sensitized wild type (WT) mice. IM infiltration into hapten challenged skin of sensitized TLR4−/− was absent at 6 hrs. post-challenge and was accompanied by absent skin mRNA expression of CXCL1, CXCL2, IFNγ, GCSF, TNFα, and CCL20. Whereas hapten primed CD8 T cells from sensitized TLR4−/− mice transferred CHS responses to challenged naïve WT mice, transfer of hapten-primed WT CD8 T cells to naïve TLR4−/− mice failed to elicit CHS responses. IM isolated from the bone marrow of sensitized WT mice and transferred at hapten challenge to sensitized TLR4−/− mice restored the absent CHS response and challenged skin expression of CXCL2, IFNγ, and G-CSF mRNA. These results indicate that TLR4 signaling is required for the bone marrow development of IM that are critical for hapten-primed CD8 T cell infiltration into challenged skin during elicitation of CHS responses.

Triggering receptor expressed on myeloid cells (Trem)-1 plays important roles in UVB induced immune suppression and cutaneous carcinogenesis

Abstract American Cancer Society acknowledges that most skin cancers result from exposure to ultraviolet (UV) rays in sunlight. UVB radiation induces mutant cells as well as immune suppression. Tumors only occur when mutant cells are in an immune suppressive environment. The mechanisms for UVB induced immune suppression are yet to be fully elucidated. The goal of this work is to explore new mechanisms for UVB induced immune suppression and skin carcinogenesis by using advanced technology. Analysis of UVB exposed mouse (Nanostring) and human (RNAseq) skin shows that triggering receptor expressed on myeloid cells (TREM)-1 signal pathway is the top canonic pathway increased by UVB. TREM-1 has roles in inflammatory diseases and cancers. However, its role in UVB induced immune suppression and skin cancers is not understood. We have found by using multi-color flow cytometry that UVB induces TREM-1 expression in a subset of conventional dendritic cell type 2 (cDC2) in the draining lymph nodes (LN). TREM-1+ cDC2 cells are barely detected in normal LN and express a high level of the co-inhibitory molecule PD-L1. In functional assays, treatment of mice with a specific TREM-1 blocking peptide LP-17 significantly diminishes UVB-induced suppression of contact hypersensitivity responses that are mediated by T cells. Further, mice treated with this peptide show decreased incidence of photocarcinogenesis and reduced number of tumors. In summary, our findings demonstrate that UVB induces the development of a novel TREM-1+ cDC2 cell subset and that TREM-1 has an important role in UVB induced immune suppression and skin carcinogenesis. Importantly, our study implies new strategies for targeting TREM-1 in the prevention and treatment of UVB induced skin cancers. Supported by grants from NIH (R01AR072213 and R01AI154842)

Circadian rhythm affects the magnitude of contact hypersensitivity response in mice.

The circadian rhythm controls multiple biological processes, including immune responses; however, its impact on cutaneous adaptive immune response remains unclear. We used a well-established cutaneous type IV allergy model, contact hypersensitivity (CHS). We induced CHS using dinitrofluorobenzene (DNFB). Mice were sensitized and elicited with DNFB in the daytime or at night. In mice, a nocturnally active animal, we found that ear swelling increased when mice were sensitized at night compared with in the daytime. In addition, cell proliferation and cytokine production in the draining lymph nodes (LNs) were promoted when sensitized at night. We hypothesized that these differences were due to the oscillation of leukocyte distribution in the body through the circadian production of adrenergic hormones. Administration of a β2-adrenergic receptor (β2AR) agonist salbutamol in the daytime decreased the number of immune cells in blood and increased the number of immune cells in LNs. In contrast, a β2AR antagonist ICI18551 administration at night increased the number of immune cells in blood and decreased the number of immune cells in LNs. Accordingly, the severity of CHS response was exacerbated by salbutamol administration in the daytime and attenuated by ICI18551 administration at night. Our study demonstrated that the magnitude of adaptive CHS response depends on the circadian rhythm and this knowledge may improve the management of allergic contact dermatitis (ACD) in humans.