The immunology of contact dermatitis. A review with special reference to the pathophysiology of eczema

Hand eczema

Hand eczema is often a chronic, multifactorial disease. It is usually related to occupational or routine household activities. Exact etiology of the disease is difficult to determine. It may become severe enough and disabling to many of patients in course of time. An estimated 2-10% of population is likely to develop hand eczema at some point of time during life. It appears to be the most common occupational skin disease, comprising 9-35% of all occupational diseases and up to 80% or more of all occupational contact dermatitis. So, it becomes important to find the exact etiology and classification of the disease and to use the appropriate preventive and treatment measures. Despite its importance in the dermatological practice, very few Indian studies have been done till date to investigate the epidemiological trends, etiology, and treatment options for hand eczema. In this review, we tried to find the etiology, epidemiology, and available treatment modalities for chronic hand eczema patients.

Human keratinocyte cultures in an in vitro approach for the assessment of surfactant-induced irritation

A specific, mechanistic, in vitro approach for the assessment of human skin irritation potential is outlined for the evaluation of surfactants and the results compared with in vivo human patch test data. The level of free available surfactant monomer and the solubilization of the corn protein zein in vitro were confirmed to be related to surfactant in vivo human skin irritation potential. In vitro cytotoxicity to monolayer keratinocyte cultures could not discriminate between the moderate human skin irritant sodium dodecyl sulfate (SDS) and the mild irritants cocamidopropylbetaine (CA) and Polysorbate 20 (P20). An in vitro stratified differentiated human epidermal equivalent (HEE) exhibited reduced cytotoxicity to the test chemicals, compared with monolayer culture responses, and was able to discriminate between the toxic potential of SDS and CA. Stimulation of interleukin-1alpha release from the A431 human keratinocyte cell line reflected in vivo erythema scores more closely than cytotoxic potential, and coincided with nitric oxide production by macrophages upon exposure to A431-conditioned medium. Combination of these mechanistic assays has allowed a profile of likely in vivo human responses to be approximated. Additional knowledge of skin penetrability and rate of recovery from toxic damage would affirm these predictions.

Loss of expression of TGF-βs and their receptors in chronic skin lesions induced by sulfur mustard as compared with chronic contact dermatitis patients

BACKGROUND

Sulfur mustard (SM) is a blister-forming agent that has been used as a chemical weapon. Sulfur mustard can cause damage in various organs, especially the skin, respiratory system, and eyes. Generally, the multiple complications of mustard gas result from its alkalizing potency; it reacts with cellular components like DNA, RNA, proteins, and lipid membranes.TGF-β is a multi-functional cytokine with multiple biological effects ranging from cell differentiation and growth inhibition to extracellular matrix stimulation, immunosuppression, and immunomodulation. TGF-β has 3 isoforms (TGF-β 1, 2, 3) and its signaling is mediated by its receptors: R1, R2 and intracellular Smads molecules.TGF-β has been shown to have anti-inflammatory effects. TGF-βs and their receptors also have an important role in modulation of skin inflammation, proliferation of epidermal cells, and wound healing, and they have been implicated in different types of skin inflammatory disorders.

METHODS

Seventeen exposed SM individuals (48.47 ± 9.3 years), 17 chronic dermatitis patients (46.52 ± 14.6 years), and 5 normal controls (44.00 ± 14.6 years) were enrolled in this study.Evaluation of TGF-βs and their receptors expressions was performed by semiquantitative RT-PCR. Only TGF1 was analyzed immunohistochemically.

RESULTS

Our results showed significant decreases in the expression percentages of TGF-β 1, 2 and R1, R2 in chemical victims in comparison with chronic dermatitis and normal subjects and significant decreases in the intensity of R1 and R2 expressions in chemical victims in comparison with chronic dermatitis and normal controls. (P value < 0.05)

CONCLUSIONS

TGF-βs and their receptors appear to have a noticeable role in chronic inflammatory skin lesions caused by sulfur mustard.

Other Allergic Skin Disorders

In this chapter we discuss allergic skin disorders other than atopic dermatitis (AD): the urticaria-angioedema syndrome, allergic contact dermatitis (ACD), protein contact dermatitis (PCD), phytodermatitis, allergic photodermatitis and allergic vasculitis.

Left-handedness in asthmatic children

Left-handedness has been associated with asthma and allergic disorders. The Geschwind-Behan-Galaburda (GBG) hypothesis could explain this association. In view of previous findings, we investigated the distribution of laterality scores among asthmatic children and controls aged 4-8 years old. Seventy families with asthmatic children were administered the International Study of Asthma and Allergy in Childhood (ISAAC) questionnaire and the Edinburgh Left-handedness Inventory. A sample of 70 families with non-asthmatic, healthy children was used as controls. The majority of children had mild asthma. Ambidexterity was the main feature in the asthmatic children. A statistically significant difference in the laterality quotient (LQ) distribution was found in the group of asthmatic children with allergic rhinitis (LQ mean value in the asthmatic children with allergic rhinitis: 42.85 vs. 79.50 in the rest of the asthmatic children). These results suggest that there is a tendency towards left-handedness in asthmatic children and lend support to the GBG hypothesis.

Differential effects of detergents on keratinocyte gene expression

We have studied the effect of various detergents on keratinocyte gene expression in vitro, using an anionic detergent (sodium dodecyl sulfate), a cationic detergent cetyltrimethylammoniumbromide (CTAB), and two nonionic detergents, Nonidet P-40 and Tween-20. We measured the effect of these detergents on direct cellular toxicity (lactate dehydrogenase release), on the expression of markers for normal differentiation (cytokeratin 1 and involucrin expression), and on disturbed keratinocyte differentiation (SKALP) by northern blot analysis. As reported in other studies, large differences were noted in direct cellular toxicity. In a culture model that mimics normal epidermal differentiation we found that low concentrations of sodium dodecyl sulfate could induce the expression of SKALP, a proteinase inhibitor that is not normally expressed in human epidermis but is found in hyperproliferative skin. Sodium dodecyl sulfate caused upregulation of involucrin and downregulation of cytokeratin 1 expression, which is associated with the hyperproliferative/inflammatory epidermal phenotype found in psoriasis, wound healing, and skin irritation. These changes were not induced after treatment of cultures with CTAB, Triton X-100, and Nonidet-P40. This effect appeared to be specific for the class of anionic detergents because sodium dodecyl benzene sulfonate and sodium laurate also induced SKALP expression. These in vitro findings showed only a partial correlation with the potential of different detergents to induce clinical, biophysical, and cell biologic changes in vivo in human skin. Both sodium dodecyl sulfate and CTAB were found to cause induction and upregulation of SKALP and involucrin at low doses following a 24 h patch test, whereas high concentrations of Triton X-100 did not. Sodium dodecyl sulfate induced higher rates of transepidermal water loss, whereas CTAB treated skin showed more signs of cellular toxicity. We conclude that the action of anionic detergents on epidermal keratinocytes is qualitatively different from the other detergents tested, which might have implications for in vitro toxicology studies that use cell biologic parameters as a read-out. We would hypothesize that detergents cause skin injury by several mechanisms that include direct cellular toxicity, disruption of barrier function, and detergent specific effects on cellular differentiation, as demonstrated here for sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, and sodium laurate.

Study of persistence and loss of patch test reactions to dichromate and cobalt

Hyposensitization is a poorly understood phenomenon that refers to the conversion from a positive to a negative (or less positive) patch test. We studied 180 cement workers with contact dermatitis, who originally had a total of 163 positive patch test reactions to potassium dichromate and 98 positive reactions to cobalt chloride. They were patch tested a 2nd time after 2-6 years. On the 2nd patch test to dichromate, 103 (63%) remained positive, while reactivity decreased in 33 (20%) and 27 (17%) had become non-reactive. Cobalt sensitivity persisted in 47%, diminished in 13%, and 40% of the patch tests became non-reactive. In 10 patients with persistent patch test reactions and 10 matched patients with diminished reactions or loss of reactivity, circulating T-cell responses to dichromate and cobalt were studied in vivo. Circulating T cells that proliferated only to specific contact allergens were isolated and in all patients they were primarily CD4+. However, in patients with persistent reactions, they were CD4+ CD45RA+ (suppressor - inducer cells). These differences support an immunologic basis for hyposensitization.

High dissociation constants (pKa) of basic permeants are associated with in vivo skin irritation in man

Previously, we have investigated the relationship between dissociation constant (pKa) and skin irritation potential. In the present experiment, 12 basic compounds, with varying pKa values ranging from 1.4 to 11.2, were applied on the backs of 12 healthy adult panellists. Cutaneous reactions were measured objectively, using reflectance spectroscopy and transepidermal water loss (TEWL), and evaluated subjectively with a modified Draize scale. A positive correlation between increasing pKa and skin irritation capacity, measured either visually or by reflectance spectroscopy, was found, but only mecamylamine (pKa = 11.2) induced a significant increase in transepidermal water loss. Compounds with low pKa also induced a paradoxical vasoconstriction measured by reflectance spectroscopy. Only high pKa appeared predictive of in vivo skin irritation, and these chemicals apparently induce skin irritation with only minimal disruption of the skin barrier. A simple 1-variable model is predictive of skin irritation for this series of organic permeants with increasing pKa.

Occupational skin hazards from synthetic plastics

Epoxy and acrylic resins have numerous industrial applications but are also widely used in the household environment. These compounds are presently one of the most important sources of occupational contact dermatitis. Contact sensitization to epoxy resins is usually caused by the resin itself but hardeners or other additives, such as reactive diluents, plasticizers, fillers and pigments, can occasionally be responsible. Since completely cured epoxy resins are not sensitizers, epoxy resin sensitization is always due to the presence, in the final polymer, of uncured allergenic low molecular weight oligomers. Acrylates are now considered the fourth most common cause of contact sensitization due to resins. Unpolymerized monomers of acrylic compounds are known to be responsible for the contact allergy. Accelerators, inhibitors and catalysts, which are usually added to the acrylates to promote the polymerization process, can also sensitize. Both allergic and irritant contact dermatitis may be caused by exposure to epoxy or acrylic resins and their additives. Contact urticaria, allergic or irritant airborne contact dermatitis caused by volatile compounds, onychia and paronychia can also occur. From January of 1984 to May of 1992 we detected 39 cases of occupational allergic contact dermatitis to epoxy resin system substances and 11 cases of occupational contact sensitization to acrylic compounds. In our experience, the electronics industry as well as paint and glue related activities were the most important sources of epoxy sensitization. Dental materials and anaerobic sealants were found to be the most frequent acrylate sensitizers.

CD23/Fc epsilon R11 expression in contact sensitivity reactions: a comparison between aeroallergen patch test reactions in atopic dermatitis and the nickel patch test reaction in non-atopic individuals

The immunopathology of patch test reactions to aeroallergens in patients with atopic dermatitis (AD) has been compared to that of contact sensitivity reactions to nickel in non-atopic individuals. Both reactions were found to exhibit equivalent erythema and induration on gross examination at 48 h. Four millimetre punch biopsies were obtained at 48 h frozen, and cryostat sections stained with a panel of MoAbs. The distribution of macrophages, dermal dendritic cells, Langerhans cells, T lymphocytes and the expression of CD23 antigen was recorded. Increased numbers of dermal dendritic cells, macrophages, T lymphocytes and Langerhans cells were found in the dermal infiltrates of both the nickel patch test reactions and the aeroallergen patch test reactions compared with their respective controls. There were no significant differences between atopic patch test reaction and nickel patch test reaction samples in the tissue distribution of these cell types. There was a significant increase in CD23 expression on Langerhans cells and dermal dendritic cells in the atopic patch test reactions, whereas an increase was only observed on dendritic cells in nickel patch test reactions. No significant difference in CD23 expression was observed in the control skin samples taken from patients with AD, nickel-sensitive patients and normal controls. This study supports the hypothesis that the aeroallergen patch test reaction in atopic dermatitis is a delayed hypersensitivity reaction, yet is distinct from the contact sensitivity reaction to nickel in terms of raised expression of CD23.

Paraphenylenediamine, a contact allergen, induces oxidative stress and ICAM-1 expression in human keratinocytes

In an investigation of the role of keratinocytes in the pre-immunological phase of contact allergy, we have studied the effect of paraphenylenediamine (PPD) on cell proliferation, membrane lipid peroxidation and the expression of the intercellular adhesion molecule 1 (ICAM-1). Because PPD undergoes rapid autoxidation in the culture medium, the effect of PPD-modified medium on keratinocyte proliferation and ICAM-1 expression was also examined. PPD at low concentrations (up to 10 micrograms/ml) and with low exposure times (0.5 h) enhanced keratinocyte proliferation, but at high concentrations and with longer exposure times resulted in cell stasis and toxicity. These effects and the enhanced membrane lipid peroxidation that was also observed can be ascribed to the production of superoxide and hydrogen peroxide by the autoxidation of PPD in the medium. At non-cytotoxic concentrations, PPD induced ICAM-1 expression on the keratinocytes. PPD-modified medium was also cytotoxic to the keratinocytes and induced ICAM-1 expression in non-cytotoxic concentrations. It appeared that superoxide and hydrogen peroxide were not responsible for the cytotoxicity. These results are consistent with the view that oxidative stress may be an essential part of the pre-immunological phase in the induction of allergic contact dermatitis.

Antigen-specific IgG1-mediated epidermal cell injury: a component of contact hypersensitivity reactions in guinea pigs, measurable in vitro in full-thickness skin explants

Guinea pigs were sensitized by the topical application of either dinitrochlorobenzene (DNCB) or oxazolone on days 1, 2, 3, and 10. Seventeen days after the first treatment with the sensitizer, full-thickness 1.0-cm2 explants of untreated areas of skin were topically exposed in vitro to these contactants. Compared to the response of skin from control guinea pigs, skin from specifically sensitized animals showed a dose-related increase in the number of epidermal cells containing vacuoles. A specific increase in epidermal microblistering paralleled the increase in epidermal vacuolization. In addition, skin explants from sensitized animals (exposed to the contactant) showed a specific decrease in the incorporation of [14C]leucine. Full-thickness skin explants from unsensitized guinea pigs were sensitized in vitro by the intradermal injection of serum IgG1 fraction from oxazolone-sensitized guinea pigs. In such passively sensitized explants, the specific contactant produced an increase in the number of epidermal vacuoles, an increase in the amount of microblistering, and a decrease in the number of mast cells detectable by Giemsa staining. To elicit this specific response, the concentration of the specific contactant had to be mildly injurious, as well as antigenic. This requirement for nonspecific injury could be met by topically exposing skin explants to a nonspecific irritant followed by a sub-threshold concentration of the specific contactant. In contrast to vacuole formation and blistering, contactant-specific degranulation of mast cells (measured by the decrease in their number) did not require irritant levels of the contactant. These studies show that several components of contact sensitivity reactions can be reproduced in vitro by the passive transfer of sera containing antigen-specific immunoglobulins. Banks of such sera might, therefore, be useful in identifying (in human populations) many pre-existing sensitivities to chemical compounds.

Cell trafficking in positive and negative patch-test reactions: demonstration of a stereotypic migration pathway

The cellular and molecular events taking place during epidermal antigen exposure in sensitized individuals are principally well understood. Epidermal Langerhans cells (LC) are supposed to take up, process, and express a given foreign substance on their cell surface. The antigen is then recognized by T cells bearing the appropriate T-cell receptor (TCR). Because LC do not bear variable antigen (Ag)-specific binding sites, one could postulate that the epidermal exposure of any substance should activate LC and other cells of the skin immune system. To test this hypothesis, we analyzed immunophenotypically the cellular trafficking events in positive (n = 5) and negative epicutaneous patch-test reactions (n = 10), using a panel of monoclonal antibodies against CD1a, CD11c (Ki-M1, LeuM5), CD68 (Ki-M6), Ki-M8, and CD3 (Leu4). We can demonstrate that irrespective of whether or not an antigen will be responded to by the immune system (i.e., positive or negative test reaction), epidermal antigen exposure causes a decrease of LC density in the epidermis and simultaneously causes an increase of LC in the dermis. Moreover, monocytes and T cells immigrate into the dermis both in positive and negative patch-test reactions. As is to be expected, the degree of this cellular traffic is more pronounced in positive test reactions, which may be due to amplification mechanisms caused by antigen recognition of sensitized T cells. This finding demonstrates that human skin contains cell migration programs that ensure that any foreign substance will be accessible to the skin immune and phagocytic system.

Recombinant human interleukin-8 is a potent activator of canine neutrophil aggregation, migration, and leukotriene B4 biosynthesis

Interleukin-8 (IL-8), formerly known as NAP-1, is formed by a variety of cells upon stimulation with IL-1 or tumor necrosis factor (TNF). The biologic activity of the cytokine involves activation of almost every neutrophil function studied so far in different species. In the present study, we compared the effects of recombinant human IL-8 (rIL-8) and the lipid mediators, leukotriene B4 (LTB4) and platelet-activating factor (PAF), on neutrophil functions in dogs. All three chemotactic factors induced neutrophil aggregation and chemotaxis, with rIL-8 being far more potent than LTB4 and PAF. The migration induced by rIL-8 was significantly greater than that observed towards LTB4 and PAF. In the aggregation assay, rIL-8 was shown for the first time to be a potent stimulant. The aggregation response was more persistent than that obtained with LTB4 and PAF and the potency of rIL-8 was greater. An intradermal dose-response study showed that rIL-8 is an extremely potent inducer of selective neutrophil infiltration in canine skin. The infiltration was more pronounced than following injection of LTB4 or PAF. It was proposed that the superior effect of rIL-8 was caused by a synergistic effect between injected rIL-8 and LTB4, which was shown to be produced in biologically active amounts by canine neutrophils stimulated with rIL-8. From a therapeutic point of view, the simultaneous presence of rIL-8 and LTB4 in inflammatory skin diseases highlights the need to develop drugs that inhibit the production and/or effect of both mediators.

Effects of interleukin-1 alpha on migration of canine neutrophils in vitro and in vivo

Inflammatory cell activation by interleukin-1 (IL-1) has been the subject of studies in laboratory animals and man, and was the aim of the present study. At physiological concentrations of 0.01-100 units/ml, human recombinant IL-1 alpha was shown to be a chemokinetic and chemotactic agent for canine neutrophils in vitro and to cause dose-dependent and selective neutrophil infiltration following intradermal injection of 1 or 250 units. The findings support a putative role for IL-1, and IL-1-induced products such as IL-8, as mediator of immunoinflammatory reactions in which neutrophil infiltration is prominent.

Dominance of memory over naive T cells in contact dermatitis is due to differential tissue immigration

CD4+ T cells include a naive (CD4-, CD45RO-, CD29-, CD45RA+) as well as a memory subpopulation (CD4+, CD45RO+, CD29+, CD45RA-). These subpopulations represent different stages in T-cell development and function. Recently, it has been shown that inflammatory and neoplastic CD4+ T-cell infiltrates are dominated by the memory subpopulation, whereas both subpopulations are about the same size in the peripheral blood. This was thought to be the result of in situ maturation of naive into memory T cells. We analysed early positive patch-test reactions 1-2 days after antigen challenge and found that most of the CD4+ T cells that had freshly immigrated into the tissue carried the memory phenotype. Their preferential migration may be mediated by at least five adhesion molecules expressed on their cell surface. This observation has important pathogenetic implications, since memory T cells can be rapidly activated by antigens and secrete a wide variety of pro-inflammatory cytokines.

Lymphocyte transformation test for diagnosis of isothiazolinone allergy in man

The lymphocyte transformation test (LTT) has been used for evaluation of in vitro lymphocyte responses in 18 patients with dermatitis and positive patch tests to 200 ppm of a combination of 5-chloro-2-methylisothiazolinone and 28methylisothiazolinone (MCI) in nine patients with dermatitis unrelated to MCI and in seven subjects without skin diseases. Two workers sensitized by occupational exposure to a formulation containing 1,2-benzisothiazolin-3-one (BIT) were also studied. Lymphocytes from nine patch-test-positive patients proliferated vigorously to MCI in vitro. Lymphocytes from the remaining nine patients were not stimulated. Lymphocytes from two BIT-sensitized workers responded to BIT in vitro. The lymphocyte proliferation to isothiazolinones indicates the presence of memory cells in the patients' blood and confirms immunologic reaction to the inducing agent. To establish clinical relevance of LTT results, 12 MCI patch-test-positive patients underwent "use test" with lotion containing 15 ppm MCI. Four of five LTT-positive patients were use-test-positive, whereas seven of seven LTT-negative patients were use-test-negative. LTT-positive and lotion-positive patients responded to 100 ppm or lower concentrations of MCI on patch testing, whereas seven of eight LTT-negative and lotion-negative patients responded to 200 ppm only. In the case of MCI, proliferation was due to the chlorinated component, indicating that this part contains an allergenic epitope. Finally, MCI-specific lymphocyte proliferation was observed only in patients with MCI-positive skin test, but not in nine patients with dermatitis induced by other agents, or in seven subjects without skin diseases. Thus, the lymphocyte transformation test is able to distinguish between irritant and allergic skin responses. It may also be valuable in establishing the clinically relevant patch-test concentration of allergens with irritative properties.

Nickel-keratinocyte interaction: a possible role in sensitization

Normal human keratinocytes and the keratinocyte-derived cell lines NCTC 2544 and A 431, were exposed for different periods (1-5 days) to various concentrations (0.023-46.6 micrograms/ml) of nickel (Ni2+). A dose- and time-dependent inhibition of cell growth and viability was observed. Cultures exposed to 2.3 micrograms Ni2+/ml showed approximately 50% cell survival at 5 days. An increase in release of interleukin 1 by keratinocytes was detected following culture for 24 h with a Ni2+ concentration of 2.3-11.5 micrograms/ml. Short periods of incubation (30 min) with these concentrations induced an activation of lipoxygenase in leucocytes from healthy subjects, without modifying cell viability. The results suggest that the percutaneous penetration of small amounts of Ni2+ can result in damage to keratinocytes and can initiate sensitization.