Ultraviolet radiation and the contact hypersensitivity reaction in mice

The article reviews the application of the contact hypersensitivity assay in mice to the science of photoimmunology. The contact hypersensitivity (CHS) reaction, which is suppressed by UV irradiation in mice similarly to their ability to respond immunologically to skin tumors, has been used very profitably to reveal many of the regulating factors that control photoimmunosuppression, such as the identity of the photoreceptors that initiate immunosuppression, the defects induced in the cutaneous antigen presenting pathway, the local cytokine imbalance, and the protective intervention by various molecules, drugs, or interacting UV wavebands. Technical hints to optimize the measurement of the CHS response are suggested, including information on UV radiation wavebands and dosages and sensitivities of different mouse strains.

Cell surface and cytokine phenotypes of skin immunocompetent cells involved in ultraviolet-induced immunosuppression

Immunocellular migrations out of and into the skin and modulations of functional cell surface molecules on antigen-presenting cells (APCs), as well as their immunoregulatory cytokine production, are important factors involved in the mechanism of UV-induced immunosuppression and tolerance. Of particular interest here are the effects of low-dose UVB exposures that can suppress the ability of a contact sensitizer to induce contact hypersensitivity (CHS) through the site (local immunosuppression) without inducing suppression of CHS induced through skin distant to the UV exposure. Such UV-irradiated skin has many changes with respect to composition of immunocompetent cells and cytokine production. After UV exposure, Langerhans cells/dendritic cells migrate from the skin to draining lymph nodes (DLNs) as they do from contact sensitizer-applied normal skin. On the other hand, UV causes monocytic/macrophagic cells to infiltrate into the dermis and then into the epidermis; these can also be shown to be induced by contact sesitizers to migrate to DLNs. Alterations in cell surface and immunoregulatory cytokine phenotypes of the cutaneous APCs in both the skin and DLNs are critical for CHS suppression and tolerance induction. Here we describe the phenotypic changes of immunocompetent cells in UV-irradiated skin in regard to CHS suppression and tolerance and methodologies to approach this area.

Measurement of ultraviolet radiation-induced suppression of recall contact and delayed-type hypersensitivity in humans

This article describes methodology used for assessment of ultraviolet radiation-induced suppression of recall responses in humans. Nickel allergy is common in the general population and patch testing of nickel-allergic volunteers provides a convenient model of contact hypersensitivity. Similarly, Mantoux-positive volunteers, recruited from within hospital staff, are used as a model for delayed-type hypersensitivity. Use of secondary rather than primary immune responses allows placement of multiple test sites on each volunteer. Further, each volunteer acts as his or her own unirradiated control. This enables UV immunosuppression to be studied with relatively few human volunteers, and makes determination of UV immunosuppression dose responses feasible in human subjects. The method can also be used for assessment of the level of immune protection afforded by agents such as sunscreens or biologically active substances.

IL-2-IgG2b fusion protein suppresses murine contact hypersensitivity in vivo

Interleukin-15 shares several functional properties with interleukin-2, and signals through the beta and gamma chain of the interleukin-2 receptor as well as through its own high affinity alpha chain. In agreement with the concept that interleukin-2 plays a key role in type IV immune responses, we have recently shown that an IL-2-IgG2b fusion protein potently suppresses Th1-type delayed type hypersensitivity reaction and Th2-type allergic sensitization in mice. We have now compared the in vivo effects of IL-2-IgG2b fusion protein with those of IL-15-IgG2b fusion protein in a murine model of Th1-type contact hypersensitivity reaction. Daily systemic injections of IL-2-IgG2b fusion protein during the sensitization phase or application of IL-2-IgG2b fusion protein just 2 h before and 10 h after antigen challenge significantly inhibited the contact hypersensitivity ear swelling response, and this without any overt signs of associated toxicity. Even local injection of IL-2-IgG2b fusion protein into the earlobe around the time of antigen challenge inhibited the ear swelling reaction significantly. In contrast, neither systemic nor local injection of the IL-15-IgG2b fusion protein modulated the contact hypersensitivity reaction significantly. IL-2-IgG2b but not IL-15-IgG2b fusion protein reduced migration of antigen-presenting cells from the skin to local lymph nodes, inhibited the expression of CD80 and CD86, and induced a significant higher number of CD4+CD25+ T cells. Therefore, the IL-2-IgGb fusion protein offers a powerful tool for suppressing and/or preventing T-cell-mediated hypersensitivity reaction in vivo.

Orthodontic appliances made of organic polymer used in the metal allergic patient can withstand orthognathic surgery

We developed an orthodontic appliance completely made of organic polymer. The appliance was used for many years and proved very effective. It was used for the treatment of patients with metal allergy, and as a result, it is believed to be the best choice for treating metal allergies. In this report, we are presenting a surgical case with Class III malocclusion for a patient with metal allergy, and the concept of the appliance is briefly discussed.

Adverse reactions to wound dressings

This article describes the potential risks to patients' skin from the use of wound dressings and how to minimise those risks. Guidance is provided on the steps to be taken once an allergic reaction is suspected.

Catecholamines inhibit the antigen-presenting capability of epidermal Langerhans cells

The sympathetic nervous system modulates immune function at a number of levels. Within the epidermis, APCs (Langerhans cells (LC)) are frequently anatomically associated with peripheral nerves. Furthermore, some neuropeptides have been shown to regulate LC Ag-presenting function. We explored the expression of adrenergic receptors (AR) in murine LC and assessed their functional role on Ag presentation and modulation of cutaneous immune responses. Both purified LC and the LC-like cell lines XS52-4D and XS106 expressed mRNA for the ARs alpha(1A) and beta(2). XS106 cells and purified LC also expressed beta(1)-AR mRNA. Treatment of murine epidermal cell preparations with epinephrine (EPI) or norepinephrine inhibited Ag presentation in vitro. Furthermore, pretreatment of epidermal cells with EPI or norepinephrine in vitro suppressed the ability of these cells to present Ag for elicitation of delayed-type hypersensitivity in previously immunized mice. This effect was blocked by use of the beta(2)-adrenergic antagonist ICI 118,551 but not by the alpha-antagonist phentolamine. Local intradermal injection of EPI inhibited the induction of contact hypersensitivity to epicutaneously administered haptens. Surprisingly, injection of EPI at a distant site also suppressed induction of contact hypersensitivity. Thus, catecholamines may have both local and systemic effects. We conclude that specific ARs are expressed on LC and that signaling through these receptors can decrease epidermal immune reactions.

Anti-allergic effects of cnidii monnieri fructus (dried fruits of Cnidium monnieri) and its major component, osthol

Anti-allergic effects (types I and IV) of the 70% ethanol extract (CM-ext) obtained from Cnidii Monnieri Fructus (dried fruits of Cnidium monnieri) were investigated on 48 h homologous passive cutaneous anaphylaxis (PCA), 2, 4-dinitrofluorobenzene (DNFB)-induced contact dermatitis and picryl chloride (PC)-induced contact dermatitis in experimental animals. CM-ext showed inhibitory effects on these allergic models. Osthol isolated from CM-ext also had the inhibitory effects. These results suggested that Cnidii Monnieri Fructus might be useful as an agent for allergic diseases and that its anti-allergic effect was partially attributable to a coumarin derivative, osthol.

Non-animal testing strategies for assessment of the skin corrosion and skin irritation potential of ingredients and finished products

The dermatotoxicologist today is faced with a dilemma. Protection of workers and consumers from skin toxicities (irritation and allergy) associated with exposure to products, and the ingredients they contain, requires toxicological skin testing prior to manufacture, transport, or marketing. Testing for skin corrosion or irritation has traditionally been conducted in animals, particularly in rabbits via the long established Draize test method. However, this procedure, among others, has been subject to criticism, both for its limited predictive capacity for human toxicity, as well as for its use of animals. In fact, legislation is pending in the European Union which would ban the sale of cosmetic products, the ingredients of which have been tested in animals. These considerations, and advancements in both in vitro skin biology and clinical testing, have helped drive an intensive effort among skin scientists to develop alternative test methods based either on in vitro test systems (e.g. using rat, pig or human skin ex vivo, or reconstructed human skin models) or ethical clinical approaches (human volunteer studies). Tools are now in place today to enable a thorough skin corrosion and irritation assessment of new ingredients and products without the need to test in animals. Herein, we describe general testing strategies and new test methods for the assessment of skin corrosion and irritation. The methods described, and utilized within industry today, provide a framework for the practicing toxicologist to support new product development initiatives through the use of reliable skin safety testing and risk assessment tools and strategies.

A critique of assumptions about selecting chemical-resistant gloves: a case for workplace evaluation of glove efficacy

Wearing chemical-resistant gloves and clothing is the primary method used to prevent skin exposure to toxic chemicals in the workplace. The process for selecting gloves is usually based on manufacturers' laboratory-generated chemical permeation data. However, such data may not reflect conditions in the workplace where many variables are encountered (e.g., elevated temperature, flexing, pressure, and product variation between suppliers). Thus, the reliance on this selection process is questionable. Variables that may influence the performance of chemical-resistant gloves are identified and discussed. Passive dermal monitoring is recommended to evaluate glove performance under actual-use conditions and can bridge the gap between laboratory data and real-world performance.

Contribution of Langerhans cell-derived IL-18 to contact hypersensitivity

The epidermal Langerhans cells (LC), a member of the dendritic cell family, and the LC-derived cytokine IL-12 play a pivotal role in the initiation of contact hypersensitivity (CHS), a Th1 immune response in the skin. Because IL-18, another LC-derived cytokine, shares functional and biological properties with IL-12, we examined a potential role for IL-18 in CHS initiation. Our studies demonstrated that during the induction phase of murine CHS, IL-18 mRNA was significantly up-regulated in the skin-draining lymph nodes (LN). Migratory hapten-modified LC in LN expressed high levels of IL-18 mRNA and secreted functional IL-18 protein. LN cells produced significant amounts of IFN-gamma following in vitro IL-12 stimulation, which could be partially blocked by anti-IL-18 Ab, suggesting a synergistic role for endogenous IL-18 in IFN-gamma production by LN cells. Because mature IL-18 requires cleavage of immature precursors by caspase-1, we further examined IL-12-induced IFN-gamma production in caspase-1(-/-) LN cells. An impaired IFN-gamma production was seen in caspase-1(-/-) LN cells, which could be restored by addition of exogenous IL-18, supporting a role for caspase-1-cleaved, mature IL-18 in IFN-gamma production. Finally, in vivo studies showed that CHS responses were significantly inhibited in mice treated with neutralizing IL-18 Ab as well as in caspase-1(-/-) mice deficient in mature IL-18, indicating functional relevance for IL-18 in CHS. Taken together, our studies demonstrate that LC-derived IL-18 significantly contributes to CHS initiation.

IFN-gamma-inducible protein 10 (IP-10; CXCL10)-deficient mice reveal a role for IP-10 in effector T cell generation and trafficking

IFN-gamma-inducible protein 10 (IP-10, CXCL10), a chemokine secreted from cells stimulated with type I and II IFNs and LPS, is a chemoattractant for activated T cells. Expression of IP-10 is seen in many Th1-type inflammatory diseases, where it is thought to play an important role in recruiting activated T cells into sites of tissue inflammation. To determine the in vivo function of IP-10, we constructed an IP-10-deficient mouse (IP-10(-/-)) by targeted gene disruption. Immunological analysis revealed that IP-10(-/-) mice had impaired T cell responses. T cell proliferation to allogeneic and antigenic stimulation and IFN-gamma secretion in response to antigenic challenge were impaired in IP-10(-/-) mice. In addition, IP-10(-/-) mice exhibited an impaired contact hypersensitivity response, characterized by decreased ear swelling and reduced inflammatory cell infiltrates. T cells recovered from draining lymph nodes also had a decreased proliferative response to Ag restimulation. Furthermore, IP-10(-/-) mice infected with a neurotropic mouse hepatitis virus had an impaired ability to control viral replication in the brain. This was associated with decreased recruitment of CD4(+) and CD8(+) lymphocytes into the brain, reduced levels of IFN-gamma and the IFN-gamma-induced chemokines monokine induced by IFN-gamma (Mig, CXCL9) and IFN-inducible T cell alpha chemoattractant (I-TAC, CXCL11) in the brain, decreased numbers of virus-specific IFN-gamma-secreting CD8(+) cells in the spleen, and reduced levels of demyelination in the CNS. Taken together, our data suggest a role for IP-10 in both effector T cell generation and trafficking in vivo.

Inhibition of contact hypersensitivity reaction to picryl chloride: effect of small molecular weight peptidomimetic compounds possessing inhibitory activity against metalloproteinases

We have studied the effect of small molecular weight inhibitors of snake venom metalloproteinases (SVMP) and matrix metalloproteinases (MMPs) on the induction and effector phase of the contact hypersensitivity reaction (CHR) in a mouse model. Identification of nonsteroid small molecules is very important for the development of new anti-inflammatory drugs. The compounds that we tested were synthetically modified tripeptides (peptidomimetic compounds) POL-257, POL-509, POL-443, POL-491, and POL-647, with structures based on natural occurring peptides in snake venom. A well-known hydroxamate-based inhibitor of the MMPs, Batimastat (BB-94), was also used. We have shown that these peptidomimetics possess in vitro inhibitory activity against the MMP-2 (gelatinase-A), MMP-9 (gelatinase-B), and MMP-3 (stromelysin). They also inhibit metalloproteinases purified from the venom of Crotalus adamanteus and C. atrox snakes, which are very similar to the so-called A Desintegrine, A Metalloproteinase (ADAMs) enzymes. When injected intraperitonealy before the topical application of the contact sensitizer (picryl chloride) or before the challenge, these compounds significantly inhibited the development of CHR. BB-94 at doses 0.4 and 4 mg/kg before the sensitization or before the challenge almost completely abrogated the reaction. POL-257 and POL-443 were among the most active peptidomimetics tested. They inhibited the inflammatory reaction up to 70-80%, when applied either immediately before sensitization or before challenge. POL-509, a methylated derivative of POL-257, inhibited the CHR to 40-50% when administered at either challenge or sensitization. However, when applied 24 h before the challenge, it completely abrogated the inflammatory reaction. The results show that these small molecular weight peptidomimetic compounds, as well as BB-94, are able to significantly inhibit the CHR. This finding opens possibilities for using metalloproteinase inhibitors in the treatment of allergic contact dermatitis and other inflammatory diseases.

Skin inflammation during contact hypersensitivity is mediated by early recruitment of CD8+ T cytotoxic 1 cells inducing keratinocyte apoptosis

Contact hypersensitivity (CHS) is a T cell-mediated, Ag-specific skin inflammation induced by skin exposure to haptens in sensitized individuals. Th1/T cytotoxic 1 cells are effector cells of CHS, whereas Th2/T regulatory CD4(+) T cells have down-regulating properties. We have previously shown that CHS to 2,4-dinitrofluorobenzene is mediated by specific CD8(+) effector cells, whose cytolytic activity is mandatory for induction of skin inflammation. In this study, using immunohistochemistry and RT-PCR analysis, we show that CD8(+) T cells are rapidly recruited into the skin at the site of hapten challenge before the onset of clinical and histological signs of skin inflammation. This early CD8(+) T cell recruitment is concomitant with: 1) transient IFN-gamma mRNA expression suggesting local activation of effector cells; and 2) induction of keratinocyte (KC) apoptosis which gradually increased to a maximum at the peak of the CHS response. Alternatively, skin infiltration of CD4(+) T cells occurred later and coincided with the peak of the CHS reaction and the beginning of the resolution of skin inflammation. Mice deficient in CD8(+) T cells did not develop CHS, whereas mice deficient in CD4(+) T cells developed an enhanced inflammatory response with increased numbers of CD8(+) T cells recruited in the skin associated with massive KC apoptosis. These data show that CHS is due to the early and selective recruitment in the skin of CD8(+) T cytotoxic 1 effector cells responsible for KC apoptosis.

Occupational dermatitis from a one-component naphthalene type epoxy adhesive

In an electronics plant, a new one-component naphthalene type epoxy resin was used as an adhesive for reinforcing a circuit board. The resinous part of the adhesive consisted of diglycidyl ether of bisphenol A (DGEBA) and 1,6-bis(2,3-epoxypropoxy)naphthalene type epoxy resins. The hardener was methylhexahydrophthalic anhydride (MHHPA). Of 54 workers, 15 (27.8%) were diagnosed to have work-related dermatitis but were not patch tested. Therefore, it was impossible to determine the specific agent responsible for the worker's symptoms or to distinguish between allergic and irritant contact dermatitis. They worked without protective gloves until they started to develop skin symptoms. The hands were the commonly affected region (13 out of 15 cases). The latent period of dermatitis was very short (mean 2.2 weeks). Of these, 10 cases (66.7%) received medication for dermatitis, and 9 cases (60%) were transferred to other work. The work-related skin symptoms were closely related to the specific tasks, i.e., filling dispensers with the adhesive and manual application of the adhesive to a portion of a circuit board using a dispenser. For occupational hygiene reasons, contact with epoxy resins should be minimized by taking all possible measures into use, including protective gloves. Further studies are required to clarify the allergenicity of 1,6-bis(2,3-epoxypropoxy)naphthalene, since very little is known about the mechanism through which it leads to the symptoms of dermatitis.

Evidence that ultraviolet B radiation transiently inhibits emigration of Langerhans cells from exposed epidermis, thwarting contact hypersensitivity induction

Langerhans cells (LC) play a critical role in the induction of contact hypersensitivity (CH), and ultraviolet B radiation (UVR) impairs CH induction in UVB-susceptible (UVB-S) mice via a TNF-alpha-dependent mechanism. A possible explanation of this effect is that UVR impairs CH in UVB-S mice by immobilizing LC transiently in the epidermis and upper dermis, thereby preventing their timely migration to draining lymph nodes. To test this hypothesis we examined in vitro and in vivo the effects of in vivo UVR on migration of Ia(+) cells from skin of UVB-S and UVB-resistant (UVB-R) mice. Dorsal surfaces of ears of mice were irradiated with 400 J/cm(2) UVB and either explanted in vitro or transplanted orthotopically to the thoracic wall of syngeneic recipients. After 24, 48, and 72 h the epidermis was recovered from these explants/grafts and the number of Ia(+) cells determined by immunohistochemistry. Culture medium obtained after explants were removed was also evaluated for content of Ia(+) cells. The density of Ia(+)-bearing cells in the epidermis of cultured untreated skin explants and of grafted skin fell progressively for both UVB-S and UVB-R skin during the observation period. The rate of decline in Ia(+) cells density during this interval was greatly impaired if the skin was exposed to UVR prior to excision; this effect was seen equally in UVB-S and UVB-R skin. Recovery of Ia(+) cells in the medium after removal of cultured untreated skin explants was maximum after 24 h and comparable in UVB-S and UVB-R skin. However, the number of Ia(+) cells recovered in the medium from UVB-exposed skin was significantly reduced only if the skin donor was UVB-S. We conclude that the ability of UVR to impede LC migration from epidermis is significantly greater for UVB-S mice, accounting in part for the failure of these mice after UVR to acquire CH.

IL-12 prevents the inhibitory effects of cis-urocanic acid on tumor antigen presentation by Langerhans cells: implications for photocarcinogenesis

UV radiation induces skin cancer primarily by its DNA-damaging properties, but also by its capacity to suppress the immune system. The photoisomer of urocanic acid (UCA), cis-UCA, is an important mediator of UV-induced immunosuppression and is involved in the inhibition of tumor immunity. The immunomodulatory cytokine IL-12 is known to counteract many of the immunosuppressive effects of UV radiation, including UV-induced immune tolerance. In this study, we addressed whether IL-12 also reverts the immunosuppressive activities of cis-UCA. Cis-UCA inhibits the ability of Langerhans cells to present tumor Ags for primary and secondary tumor immune responses. IL-12 treatment completely prevented the suppression by cis-UCA. IL-12 also protected mice from cis-UCA-induced suppression of contact hypersensitivity responses. To study the effects of cis-UCA on Ag-processing and Ag-presenting function in vitro, Langerhans cells were treated with UCA isomers and incubated with OVA or OVA peptide(323-339) before exposure to OVA-specific transgenic T cells. Cis-, but not trans-UCA suppressed Ag presentation, which was completely reversed upon addition of IL-12. Since these findings suggest that cis-UCA may play an important role in photocarcinogenesis by inhibiting a tumor immune response, mice were chronically UVB irradiated to induce skin cancer. Whereas all mice in the control groups developed tumors, mice treated with a mAb with specificity for cis-UCA showed a significantly reduced tumor incidence. These data strongly indicate the importance of cis-UCA during photocarcinogenesis and support the concept of counteracting cis-UCA as an alternative strategy to prevent UV-induced skin cancer, possibly via the application of IL-12.

Mitigation of stress-induced suppression of contact hypersensitivity by odorant inhalation

BACKGROUND

Various skin functions are affected by stress. We have previously shown that odorant inhalation can regulate skin immune reactions.

OBJECTIVES

To test the hypothesis that certain odorants can mitigate the effects of stress on skin immune reactions.

METHODS

Contact hypersensitivity (CH) reactions were elicited in C57BL/6 mice. Mice were subjected to immobilization stress and were exposed to odorants for 2 days. Epidermal sheets were stained for I-A antigens and analysed by confocal laser scanning microscopy. Serum corticosterone levels were assayed by radioimmunoassay.

RESULTS

Exposure of mice to 1,3-dimethoxy-5-methylbenzene (DMMB) had no effect on the intact CH reaction, but it upregulated the reaction suppressed by immobilization stress. Other odorants, including terpinyl acetate and valerian oil, had minor effects on the CH reaction. Suppression of I-A-positive cells was prevented by DMMB inhalation. Valerian oil, but not DMMB, downregulated stress-induced plasma corticosterone levels.

CONCLUSIONS

Results suggest that odorant inhalation modulates various physiological pathways, some of which result in regulation of skin function.

Stress response, tachykinin, and cutaneous inflammation

In the last decade, several new aspects of glucocorticoid (GC)-actions on immune cells have been recognized. This recognition has been largely obtained through clinical observations of stress-induced exacerbations of certain dermatologic diseases. To clarify whether GC modulates cutaneous inflammatory reactions besides its known anti-inflammatory effect, first we examined the effect of long-term application of topical GC on several kinds of inflammatory responses induced in the murine model and demonstrated that these regimens significantly augmented the classical contact sensitivity reaction, the croton oil-induced irritant reaction, and the IgE-mediated biphasic cutaneous reaction. In addition, large dose topical steroid and its withdrawal enhanced scratching behavior in hapten-challenged mice. This augmented scratching behavior correlated with the induction of preprotachykinin mRNA expression in the challenged skin. In an in vitro experiment, a low-dose, stress-induced level of glucocorticoid significantly upregulated hapten-induced proinflammatory cytokine (IL1alpha) production by murine keratinocyte cell line Pam 212 and induced substance P peptide production from cultured human keratinocytes. Our results suggest that unsuitable use of GC in addition to stress-induced GC may modulate immune function in the skin through aberrant production of tachykinin, such as substance P or other epidermal cell derived cytokines.

Current and future issues in sensitisation testing

Sensitisation is one of the biological risks that needs to be addressed for any medical device before clearance or clinical evaluation. This article describes the state of the art for this evaluation and also new variants of the procedure to increase the accuracy of these tests, particularly when some metals, latex-based products and macromolecular proteins such as collagen are concerned.

Are barrier creams actually effective?

This article reviews the current information surrounding the efficacy of barrier creams as a protective measure against contact dermatitis. The principles of the proposed effects of barrier creams on the skin and the experimental and clinical data regarding their efficacy in the prevention of irritant and allergic contact dermatitis are discussed.

Carcinogen-induced inflammation and immunosuppression are enhanced in xeroderma pigmentosum group A model mice associated with hyperproduction of prostaglandin E2

Xeroderma pigmentosum group A (XPA) gene-deficient mice easily developed skin cancers by the application of topical chemical carcinogens as well as by UV irradiation. As certain chemical carcinogens have been shown to be immunosuppressive, we examined the inflammatory and immunosuppressive effects of dimethylbenz(a)anthracene (DMBA) on XPA mice. Compared with wild-type mice, XPA mice showed greater ear swelling and reduction of epidermal Langerhans cells after DMBA application. Topical application of DMBA impaired the induction of contact hypersensitivity, initiated either locally or at distant sites. These DMBA-induced local and systemic immunosuppressions were more greatly enhanced in XPA mice than in wild-type mice. DMBA application induced pronounced production of PGE(2), IL-10, and TNF-alpha in the skin of XPA mice. Treatment with indomethacin, a potent inhibitor of PG biosynthesis, inhibited DMBA-induced inflammation and local immunosuppression. In XPA mice, increased serum IL-10 was detected after DMBA treatment. Excess production of PGE(2), TNF-alpha, and IL-10 after DMBA application may be involved in the enhanced local and systemic immunosuppression in DMBA-treated XPA mice. Susceptibility to DMBA-induced skin tumors in XPA mice may be due to easy impairment of the immune system by DMBA in addition to a defect in the repair of DMBA-DNA adduct. Enhanced immunosuppression by chemical carcinogens as well as the mutagenicity of these mutagens might be associated with the high incidence of internal malignancies seen in XP patients. Moreover, these results supported the hypothesis that persistent DNA damage is a trigger for the production of immunoregulatory cytokines.

Effect of different moisturizers on SLS-irritated human skin

Moisturizers are widely used to treat irritant contact dermatitis (ICD). Their use is, however, not well-documented and standardized models for testing skin care products are needed to acquire documentation of their efficacy. The present study was undertaken to evaluate the effect of 6 commonly-used moisturizers on the recovery of irritated human skin. No commercial interests were involved in the study. 36 healthy volunteers had patch tests with SLS 0.5% applied on their forearms/upper arms for 24 h. After irritation of the skin, all volunteers had a moisturizer applied on one forearm/upper arm, respectively, 3 x daily for the following 5 days. The other forearm/upper arm served as an untreated control. Each moisturizer was tested on 12 volunteers and each volunteer tested 2 moisturizers at the same time. Evaluation was done on days 1, 3 and 8 by transepidermal water loss, electrical capacitance, laser Doppler flowmetry, DermaSpectrometry and clinical scoring. All 6 moisturizers were found to accelerate regeneration of the skin barrier function when compared to irritated non-treated skin. The most lipid-rich moisturizers improved barrier restoration more rapidly than the less lipid-rich moisturizers. We suggest this experimental model for further moisturizer efficacy testing.

Functional caspase-1 is required for Langerhans cell migration and optimal contact sensitization in mice

Langerhans cell (LC) migration from epidermis to draining lymph node is a critical first step in cutaneous immune responses. Both TNF-alpha and IL-1 beta are important signals governing this process, but the potential regulatory role of IL-1 alpha processing by caspase-1 is unknown. In wild-type (WT) mice, application of the contact allergens 2,4-dinitrofluorobenzine and oxazolone lead to a marked reduction in epidermal LC numbers, but in caspase-1-deficient mice this reduction was not observed. Moreover, although intradermal injection of TNF-alpha (50 ng) induced epidermal LC migration in WT mice, this cytokine failed to induce LC migration in caspase-1-deficient mice. Intradermal IL-1 beta (50 ng) caused a similar reduction in epidermal LC numbers in both WT and caspase-1-deficient mice, indicating that, given an appropriate signal, caspase-1-deficient epidermal LC are capable of migration. Contact hypersensitivity to both 2,4-dinitrofluorobenzine and oxazolone was inhibited in caspase-1-deficient mice, indicating a functional consequence of the LC migration defect. In organ culture the caspase-1 inhibitor Ac-YVAD-cmk, but not control peptide, potently inhibited the epidermal LC migration that occurs in this system, and reduced spontaneous migration of LC was observed in skin derived from caspase-1-deficient mice. Moreover, Ac-YVAD-cmk applied to BALB/c mouse skin before application of contact sensitizers inhibited LC migration and contact hypersensitivity in vivo. Taken together, these data indicate that caspase-1 may play a central role in the regulation of LC migration and suggest that the activity of this enzyme is amenable to control by specific inhibitors both in vivo and in vitro.

CD4+ and CD8+ T cell priming for contact hypersensitivity occurs independently of CD40-CD154 interactions

The primary effector cells of contact hypersensitivity (CHS) responses to dintrofluorobenzene (DNFB) are IFN-gamma-producing CD8(+) T cells, whereas CD4(+) T cells regulate the magnitude and duration of the response. The requirement for CD40-CD154 engagement during CD8(+) and CD4(+) T cell priming by hapten-presenting Langerhans cells (hpLC) is undefined and was tested in the current study. Similar CHS responses to DNFB were elicited in wild-type and CD154(-/-) animals. DNFB sensitization of CD154(-/-) mice primed IFN-gamma-producing CD8(+) T cells and IL-4-producing CD4(+) T cells. However, anti-CD154 mAb MR1 given during hapten sensitization inhibited hapten-specific CD8(+), but not CD4(+), T cell development and the CHS response to challenge. F(ab')(2) of MR1 failed to inhibit CD8(+) T cell development and the CHS response suggesting that the mechanism of inhibition is distinct from that of CD40-CD154 blockade. Furthermore, anti-CD154 mAb did not inhibit CD8(+) T cell development and CHS responses in mice depleted of CD4(+) T cells or in CD4(-/-) mice. During in vitro proliferation assays, hpLC from mice treated with anti-CD154 mAb during DNFB sensitization were less stimulatory for hapten-primed T cells than hpLC from either control mice or mice depleted of CD4(+) T cells before anti-CD154 mAb administration. These results demonstrate that development of IFN-gamma-producing CD8(+) T cells and the CHS response are not dependent on CD40-CD154 interactions. This study proposes a novel mechanism of anti-CD154 mAb-mediated inhibition of CD8(+) T cell development where anti-CD154 mAb acts indirectly through CD4(+) T cells to impair the ability of hpLC to prime CD8(+) T cells.

Self-reported skin problems among physical processors in the chemical industry in Great Britain

Contact dermatitis is common in the chemical industry. A cross-sectional study was conducted to investigate the prevalence of self-reported skin problems in employees involved in the drying, blending, milling, grinding and filling/bagging end of chemical manufacture in small- to medium-sized contract manufacturing/processing chemical companies in Great Britain. There were several secondary aims. Twenty-three per cent of the employees interviewed reported having had a skin problem in the previous 12 months. Of those reporting problems, 46% were always/nearly always involved in blending and 56% were always/nearly always involved in filling and bagging. These same processes were also more commonly associated with continuous or recurring skin problems. Seventy-five per cent reported a problem involving the upper limbs; most had more than one body area affected. Forty-three per cent had consulted a doctor (67% their general practitioner) and 9% took time off work as a result of their skin condition. Skin problems seemed to peak (34% employees) in those who had spent between 1 and 2 years in their current job. Solvents, known skin irritants, were the most frequent, single category of chemicals encountered in the study. Over 92% had been told how to avoid skin problems; 85% reported that they always/almost always wore protective clothing. Despite these measures, a significant number had reported having had a skin problem related to their work in the previous 12 months. Particular attention to control measures based on risk assessment is recommended for these physical processors in the chemical industry. Further research is also recommended into the whole area of personal protective clothing and the individual worker's perception of risks to health in the workplace.

Necessity of thromboxane A2 for initiation of platelet-mediated contact sensitivity: dual activation of platelets and vascular endothelial cells

To investigate the crucial role of platelet-derived thromboxane A(2) (TXA(2)) in initiating Ag-specific contact sensitivity (CS), a platelet-dependent CS model using genetically mast cell-deficient W/W(v) mice, was provided. In vivo treatment with BAYu3405, a TXA(2) receptor antagonist, markedly suppressed CS responses in a dose-dependent manner. This inhibitory effect occurred when BAYu3405 was administered before an early initiating phase, suggesting that TXA(2) may be a potent initiator of platelet-mediated CS responses. When platelets were pretreated with BAYu3405 in vitro, platelet aggregation as well as serotonin release, which is able to induce the early phase response allowing local recruitment of CS effector T cells due to direct activation of vascular endothelial cells, was inhibited. The addition of U46619, a TXA(2) agonist, or a mixture of platelets and thrombin-enhanced expression of both ICAM-1 and VCAM-1 on isolated mouse aortic endothelial cells, which was completely abolished by pretreatment with BAYu3405. Furthermore, intradermal injection of U46619 into the ear of platelet-depleted mice led to CS responses with marked expression of ICAM-1 and VCAM-1 on the vascular endothelium. These findings suggest that TXA(2) generated from platelets activated with Ag may mediate initiation of CS responses through inducing serotonin release from platelets and the subsequent aggregation and up-regulated expression of ICAM-1 and VCAM-1 on vascular endothelial cells.

Preservation of the delayed-type hypersensitivity response to alloantigen by xyloglucans or oligogalacturonide does not correlate with the capacity to reject ultraviolet-induced skin tumors in mice

Chronic exposure to ultraviolet radiation suppresses T cell-mediated immune responses and induces the formation of suppressor T lymphocytes that prevent the rejection of highly antigenic ultraviolet-induced skin cancers in mice. Tamarind seed xyloglucans and pectinic oligogalacturonides prevent suppression of delayed-type hypersensitivity immune responses in mice to Candida albicans and alloantigen caused by a single exposure of ultraviolet radiation. We therefore investigated the ability of these poly/oligosaccharides to prevent suppression of T cell-mediated immune responses and suppressor cell induction during chronic ultraviolet irradiation and to preserve the capacity of ultraviolet-irradiated mice to reject a transplanted, highly antigenic, ultraviolet-induced tumor. C3H/HeN mice were treated 3x per week for 12 wk with 15 kJ per m2 ultraviolet B radiation followed by application of the polysaccharides/ oligosaccharides. The delayed-type hypersensitivity responses to C. albicans and alloantigen were measured after 1, 6, and 12 wk of treatment. Following the 12th wk of treatment the remaining mice were injected with the highly antigenic ultraviolet-induced, syngeneic tumor cell line UV5497-5. The polysaccharides/oligosaccharides protected delayed-type hypersensitivity responses to C. albicans but not contact hypersensitivity responses to dinitrofluorobenzene for up to 6 wk of ultraviolet radiation after which protection declined and suppressor cells were observed. In contrast, the delayed-type hypersensitivity response to alloantigen was preserved for the entire 12 wk of ultraviolet irradiation. Despite protection of immunity to alloantigen, the transplanted tumor cells grew equally well in all ultraviolet-irradiated animals. These results indicate that delayed-type hypersensitivity responses are heterogeneous and that delayed-type hypersensitivity to alloantigen is not a surrogate marker for rejection of ultraviolet-induced skin tumors.

CD4+ Th1 and CD8+ type 1 cytotoxic T cells both play a crucial role in the full development of contact hypersensitivity

The role of CD4(+) vs CD8(+) T cells in contact hypersensitivity (CHS) remains controversial. In this study, we used gene knockout (KO) mice deficient in CD4(+) or CD8(+) T cells to directly address this issue. Mice lacking either CD4(+) or CD8(+) T cells demonstrated depressed CHS responses to dinitrofluorobenzene and oxazolone compared with wild-type C57BL/6 mice. The depression of CHS was more significant in CD8 KO mice than in CD4 KO mice. Furthermore, in vivo depletion of either CD8(+) T cells from CD4 KO mice or CD4(+) T cells from CD8 KO mice virtually abolished CHS responses. Lymph node cells (LNCs) from hapten-sensitized CD4 and CD8 KO mice showed a decreased capacity for transferring CHS. In vitro depletion of either CD4(+) T cells from CD8 KO LNCs or CD8(+) T cells from CD4 KO LNCs resulted in a complete loss of CHS transfer. LNCs from CD4 and CD8 KO mice produced significant amounts of IFN-gamma, indicating that both CD4(+) and CD8(+) T cells are able to secrete IFN-gamma. LNCs from CD8, but not CD4, KO mice were able to produce IL-4 and IL-10, suggesting that IL-4 and IL-10 are mainly derived from CD4(+) T cells. Intracellular cytokine staining of LNCs confirmed that IFN-gamma-positive cells consisted of CD4(+) (Th1) and CD8(+) (type 1 cytotoxic T) T cells, whereas IL-10-positive cells were exclusively CD4(+) (Th2) T cells. Collectively, these results suggest that both CD4(+) Th1 and CD8(+) type 1 cytotoxic T cells are crucial effector cells in CHS responses to dinitrofluorobenzene and oxazolone in C57BL/6 mice.

Long-wave UVA offers partial protection against UVB-induced immune suppression in human skin

Ultraviolet-B (UVB, 280-320 nm) interferes with the generation of cell-mediated immunity to contact allergens applied epicutaneously on the irradiated site. To investigate whether pretreatment with UVA-1 (340-400 nm) protects against the UVB-induced immune suppression we sensitized human volunteers with diphenylcyclopropenone (DPCP) on normal buttock skin (n= 12), on UVB-irradiated buttock skin (n=21), on buttock skin pretreated with UVA-1 (n= 12), and on buttock skin pretreated with UVA-1 and thereafter irradiated with UVB (n=22). Sensitization on UVB-irradiated skin reduced the immunization rate to DPCP compared with sensitization on non-irradiated skin (p<0.01) and skin pretreated with UVA-1 (p<0.01). In contrast, the immunization rate in the group of volunteers sensitized on skin pretreated with UVA-1 before UVB irradiation was significantly higher than the immunization rate in the group of volunteers sensitized on UVB-irradiated skin alone (p<0.05). These results indicate that pretreatment with UVA-1 under certain conditions offers partial protection against the UVB-induced reduction in the immunization rates to epicutaneous allergens.

Effects of infection control measures on skin of health care workers

A review of patients presenting to a contact dermatitis investigation clinic in 1999 showed that almost half (60/124) of those with occupational hand dermatitis were health care workers. The use of fragrance-free products would be a simple intervention to reduce the prevalence of allergic contact dermatitis without affecting antimicrobial efficacy; other measures are discussed.

Suppression by citrus auraptene of phorbol ester-and endotoxin-induced inflammatory responses: role of attenuation of leukocyte activation

Auraptene (AUR), a citrus coumarin derivative, is one of the promising chemopreventive agents against skin, tongue, esophagus and colon carcinogenesis in rodents. We reported previously that AUR suppresses superoxide anion (O(2)(-)) generation from inflammatory leukocytes in in vitro experiments. In the present study, we investigated the anti-inflammatory activities of AUR using a 12-O:-tetradecanoylphorbol-13-acetate-treated mouse skin model, and compared them with those of umbelliferone (UMB), a structural analog of AUR that is virtually inactive toward O(2-) generation inhibition. Double pre-treatments of mouse skin with AUR, but not UMB, markedly suppressed edema formation, hydrogen peroxide production, leukocyte infiltration, and the rate of proliferating cell nuclear antigen-stained cells. These inhibitory effects by AUR are attributable to its selective blockade of the activation stage, as revealed by single pre-treatment experiments. In a murine macrophage line, RAW 264.7, AUR significantly attenuated the lipopolysaccharide-induced protein expression of inducible isoforms of both nitric oxide synthase and cyclooxygenase, with decreased production of nitrite anion and prostaglandin E(2), and yet suppressed the release of tumor necrosis factor-alpha. Conversely, UMB did not show any inhibitory effect. This contrasting activity profile between AUR and UMB was rationalized to be a result of their distinct differences in cellular uptake efficiencies, i.e. the geranyloxyl group in AUR was found to play an essential role in incorporation. Thus, our findings indicate that AUR is an effective agent to attenuate the biochemical responsiveness of inflammatory leukocytes, which may be essential for a greater understanding of the action mechanism that underlies its inhibition of inflammation-associated carcinogenesis.

Bradykinin and nitric oxide generation by dialysis membranes can be blunted by alkaline rinsing solutions

BACKGROUND

Bradykinin (BK) generation following the first contact of blood with the dialysis materials is thought to enhance hypersensitivity reactions (HSRs). Some of the effects of BK are mediated by nitric oxide (NO). We have recently reported that the pH of diluted blood modulates the kinin system. The present study was aimed to investigate the role of the pH of culture media and filter-washing solutions and BK and NO generation, either in vitro and ex vivo.

METHODS

BK was measured by a specific enzyme-linked immunosorbent assay (ELISA), and NO synthase (NOS) activity by 3H-citrulline production after incubation with 3H-arginine and nitrites by using the Griess reagent. In in vitro experiments, NOS activity was detected in endothelial cells (ECs) cultured with graded BK concentrations at various pH values. Blood from 30 patients in regular dialysis was ex vivo circulated in one single passage through minifilters prerinsed with pH 7 or pH 8 phosphate buffer (PB) solutions. The out-flowing blood was tested for BK and nitrite content and was incubated with cultured ECs to evaluate its capacity to modulate NOS activity.

RESULTS

BK induced in vitro a dose-dependent increase in NOS activity of ECs, which was mediated by tyrosine kinase phosphorylation. NO generation was enhanced at pH 7.2, which remained unchanged at pH 7.6. In ex vivo experiments, blood out-flowing after one passage on filters washed with pH 7 PB solutions had increased BK levels (P < 0.0001), increased nitrites (P < 0.05), and enhanced EC NOS activity (P < 0. 05) in comparison to data found when filters were washed with pH 8 PB. Only when the filters were rinsed with a solution at pH 7 did PAN DX and AN69 membranes show a distinct BK generation capability, and cuprophane a peculiar capability to enhance NOS. Such effects were prevented when dialyzers were prerinsed with pH 8 PB. Multiple regression analysis showed that the pH of the uremic blood was the driving factor for BK and NOS activation (r = 0.54, P < 0.02).

CONCLUSIONS

BK and NO generation are modulated by environmental pH. Rinsing the blood and dialysate compartments of filters with an alkaline solution prior to use may mitigate the activation of mediators likely to be involved in some HSRs.

Topical application of docosanol- or stearic acid-containing creams reduces severity of phenol burn wounds in mice

Because of their reported antiviral and anti-inflammatory activities, cream formulations containing n-docosanol (docosanol) or stearic acid were tested for effects on chemically-induced burns in mice. In this model, injury was induced by painting the abdomens of mice with a chloroform solution of phenol. This was followed by the topical application of test substances 0.5, 3, and 6 h later. Progression of the wounds was assessed by a single evaluator after 8 h, using a numerical score of gross morphology. Docosanol- and stearic acid-containing creams substantially and reproducibly lessened the severity and progression of skin lesions compared to untreated sites with a 76% and 57% reduction in mean lesion scores, respectively. Untreated wounds appeared red and ulcerated; docosanol cream-treated wounds showed only slight erythema.

Lack of metallothionein-I and -II exacerbates the immunosuppressive effect of ultraviolet B radiation and cis-urocanic acid in mice

The effect of a null mutation for the metallothionein (MT)-I and -II isoforms in mice on the immunosuppressive action of ultraviolet B (UVB; 280-320 nm) radiation has been examined. Mice were exposed to a series of increasing daily UVB doses, each dose administered to the dorsum on 3 consecutive days. Erythema was assessed, and measured as its oedema component by the post-irradiation dorsal skinfold thickness, but there was no effect of the null mutation (MT-/-) observed after 3 x 3.4 kJ/m2 of UVB radiation. Immune function was assessed by the contact hypersensitivity (CHS) response, which was initiated by sensitization on unirradiated abdominal skin, and thus demonstrated the systemic effects of dorsal treatments. In comparison with the wild-type MT+/+ mouse, the MT-/- mouse was significantly more immunosuppressed by moderate daily UVB doses (1. 75-5.9 kJ/m2). When topically applied cis-urocanic acid (cis-UCA) replaced UVB radiation as the immunosuppressive agent, contact hypersensitivity in MT-/- mice was again markedly more suppressed than in MT+/+ mice, in a dose-responsive manner. The results infer that MT, which was shown immunohistochemically to be strongly induced in the epidermis of MT+/+ mice, but to be absent in MT-/- epidermis, has the potential to protect from photoimmunosuppression, and that the mechanism of action may be via the inactivation of the epidermal UVB-photoproduct, cis-UCA.

Inhibition of functional T cell priming and contact hypersensitivity responses by treatment with anti-secondary lymphoid chemokine antibody during hapten sensitization

Recent studies have suggested a pivotal role for secondary lymphoid chemokine (SLC) in directing dendritic cell trafficking from peripheral to lymphoid tissues. As an extension of these studies, we examined the consequences of anti-SLC Ab treatment during Ag priming on T cell function in an inflammatory response. We used a model of T cell-mediated inflammation, contact hypersensitivity (CHS), where priming of the effector T cells is dependent upon epidermal dendritic cell, Langerhans cells, and migration from the hapten sensitization site in the skin to draining lymph nodes. A single injection of anti-SLC Ab given at the time of sensitization with FITC inhibited Langerhans cell migration into draining lymph nodes for at least 3 days. The CHS response to hapten challenge was inhibited by anti-SLC Ab treatment in a dose-dependent manner. Despite the inhibition of CHS, T cells producing IFN-gamma following in vitro stimulation with anti-CD3 mAb or with hapten-labeled cells were present in the skin-draining lymph nodes of mice treated with anti-SLC Ab during hapten sensitization. These T cells were unable, however, to passively transfer CHS to naive recipients. Animals treated with anti-SLC Ab during hapten sensitization were not tolerant to subsequent sensitization and challenge with the hapten. In addition, anti-SLC Ab did not inhibit CHS responses when given at the time of hapten challenge. These results indicate an important role for SLC during sensitization for CHS and suggest a strategy to circumvent functional T cell priming for inflammatory responses through administration of an Ab inhibiting dendritic cell trafficking.

[Epoxy in occupational environment--an old acquaintance in a new dress]

This article describes a cluster of epoxy related contact dermatitis in a glassfibre reinforcement plant, using mostly preimpregnated epoxylaminate (Pre-Preg), but also fluid epoxy-products. An occupational medical and dermatological examination revealed nine of 26 cases as allergic contact eczema, 14 as toxic epoxyrelated eczema and three cases of other non-occupationally related skin diseases. The plant uses seven different epoxyresins with 15 epoxyhardeners. Preventive measures were gradually improved, but even then it was difficult to rule the production into safe procedures with this potent allergen used in large scale production of windmill wings.

FRAP DNA-dependent protein kinase mediates a late signal transduced from ultraviolet-induced DNA damage

Ultraviolet radiation induces signal transduction at both early (<6 h) and late (>6 h) times after exposure. The inflammatory and immunosuppressive cytokine tumor necrosis factor alpha is induced at late times, and is induced by ultraviolet-induced DNA damage, as defects in DNA repair increase, and enhanced photoproduct repair reduces, tumor necrosis factor alpha expression. Here we show that late tumor necrosis factor alpha gene expression is sensitive to rapamycin, implicating FKBP12-rapamycin-associated protein, a member of the DNA protein kinase family, as a signal transducer of ultraviolet-induced DNA damage. FKBP12-rapamycin-associated protein was localized in the nucleus of keratinocytes and its level was increased following ultraviolet irradiation. Immuno- precipitated FKBP12-rapamycin-associated protein was stimulated by ultraviolet-irradiated DNA to phosphorylate p53 in vitro, and in vivo rapamycin reduced ultraviolet induction of p53 by 20%. Rapamycin further inhibited the ultraviolet-induced phosphorylation of the FKBP12-rapamycin-associated protein downstream target kinase p70S6K. In mice, topical application of rapamycin before ultraviolet exposure protected against suppression of the contact hypersensitivity that is a hallmark of ultraviolet-induced cytokine gene expression. These results demonstrate that the FKBP12-rapamycin-associated DNA protein kinase transduces the signal of ultraviolet-induced DNA damage into production of immunosuppressive cytokines at late times after ultraviolet irradiation.

Improved protection against solar-simulated radiation-induced immunosuppression by a sunscreen with enhanced ultraviolet A protection

Ultraviolet radiation-induced immunosuppression is thought to play a part in skin cancer. Several studies have indicated that sunscreens that are designed to protect against erythema failed to give comparable protection against ultraviolet radiation-induced immunosuppression. One possible reason for this discrepancy is inadequate ultraviolet A protection. This study evaluated the level of immunoprotection in mice afforded by two broad-spectrum sunscreens with the same sun protection factor, but with different ultraviolet A protection factors. Both sunscreens contained the same ultraviolet B and ultraviolet A filters, in the same vehicle, but at different concentrations. Solar simulated radiation dose-response curves for erythema, edema, and systemic suppression of contact hypersensitivity were generated and used to derive protection factors for each end-point. The results of three different techniques for determining immune protection factor were compared. A comparison of the two sunscreens showed that the protection factor for erythema in mice was similar to that determined in humans (sun protection factor) but the protection factor for edema in mice was lower. Both sunscreens protected against suppression of contact hypersensitivity but the product with the higher ultraviolet A-protection factor showed significantly greater protection. The three techniques for determining immunoprotection gave very similar results for a given sunscreen, but immune protection factor was always lower than sun protection factor. These data suggest that sun protection factor may not predict the ability of sunscreens to protect the immune system and that a measure of ultraviolet A protection may also be necessary.

IL-10 contributes to the inhibition of contact hypersensitivity in mice treated with photodynamic therapy

We have explored the effect of photodynamic therapy (PDT) with verteporfin on the induction and expression of contact hypersensitivity (CHS) to 2,4-dinitrofluorobenzene (DNFB) in normal mice and IL-10-deficient mice. Our results indicate that DNFB sensitized mice given PDT with verteporfin and whole body red light irradiation exhibited a significant reduction in CHS compared with control animals. Administration of rIL-12 reversed the effect(s) of PDT as did treatment of mice with anti-IL-10-neutralizing Ab. Knockout mice deficient in IL-10 were found to be resistant to the inhibitory effects of PDT. In vitro proliferative responses using spleen cells from DNFB-sensitized and PDT-treated mice showed a significantly lower response to DNBS as compared with cells from DNFB-sensitized mice or DNFB and PDT-treated IL-10-deficient mice. Finally, naive mice exposed to PDT exhibited an increase in skin IL-10 levels, which peaked between 72 and 120 h post-PDT. Together these data support the role of IL-10 as a key modulator in the inhibition of the CHS response by whole body PDT.

Regulation of cutaneous allergic reaction by odorant inhalation

Olfactory stimuli modulate emotional conditions and the whole body immune system. Effects of odorant inhalation on cutaneous immune reaction were examined. Contact hypersensitivity to 2,4, 6-trinitrochlorobenzene was elicited in C57BL/6 mice. The reaction was suppressed at both the induction and elicitation phases by exposure to an odorant, citralva. Topical application of citralva or lyral/lilial did not affect the reaction. The suppressive effect of citralva was more potent than that of another odorant, lyral/lilial. Citralva decreased the number of epidermal Langerhans cells, whereas lyral/lilial had a weak effect. Citralva but not lyral/lilial induced plasma corticosterone. Glucocorticoid receptor antagonist abrogated the suppressive effect of citralva on contact hypersensitivity. Serum interleukin-12 was downregulated by exposure to citralva or lyral/lilial. These data demonstrate that olfactory stimuli regulate the cutaneous immune system.

Thymidine dinucleotides inhibit contact hypersensitivity and activate the gene for tumor necrosis factor alpha1

DNA is a target for ultraviolet-B-induced inhibition of contact hypersensitivity, and small DNA fragments such as thymidine dinucleotides (pTpT) can simulate several ultraviolet-induced effects. To determine whether pTpT mimics the suppressive influence of ultraviolet-B on contact hypersensitivity, we compared the effects of topical application of pTpT with those of ultraviolet-B irradiation on C57BL/6 mice sensitized to dinitrofluorobenzene. Mice pretreated with pTpT or ultraviolet-B irradiation showed markedly suppressed ear swelling responses to dinitrofluorobenzene challenge. Because tumor necrosis factor alpha mediates ultraviolet-B-induced suppression of contact hypersensitivity, and because pTpT exerts many ultraviolet-mimetic effects by augmenting mRNA and protein levels of effector molecules, we asked if pTpT mimics ultraviolet-B's upregulatory influence on tumor necrosis factor alpha expression. Using transgenic mice carrying a chloramphenicol acetyl transferase reporter linked to the tumor necrosis factor alpha promoter, we examined effects of ultraviolet-B irradiation versus intradermal injection of pTpT on tumor necrosis factor alpha gene transcription. Both treatments induced cutaneous chloramphenicol acetyl transferase activity. Ultra- violet-B or pTpT treatment of cultured dermal fibroblasts from these mice also stimulated chloramphenicol acetyl transferase activity. To determine whether human cells responded similarly, a well- differentiated ultraviolet-responsive human squamous cell carcinoma line was treated with pTpT. pTpT increased tumor necrosis factor alpha mRNA expression and protein secretion in a dose-dependent manner. Our findings expand the spectrum of ultraviolet effects mimicked by pTpT to include inhibition of contact hypersensitivity and activation of the tumor necrosis factor alpha gene. These results support the hypothesis that DNA photoproducts and/or their repair intermediates trigger many of the biologic consequences of ultraviolet irradiation.