IL-31: a new link between T cells and pruritus in atopic skin inflammation

BACKGROUND

IL-31 is a novel T-cell-derived cytokine that induces severe pruritus and dermatitis in transgenic mice, and signals through a heterodimeric receptor composed of IL-31 receptor A and oncostatin M receptor.

OBJECTIVE

To investigate the role of human IL-31 in pruritic and nonpruritic inflammatory skin diseases.

METHODS

The expression of IL-31 was analyzed by quantitative real-time PCR in skin samples of healthy individuals and patients with chronic inflammatory skin diseases. Moreover, IL-31 expression was analyzed in nonlesional skin of atopic dermatitis patients after allergen or superantigen exposure, as well as in stimulated leukocytes. The tissue distribution of the IL-31 receptor heterodimer was investigated by DNA microarray analysis.

RESULTS

IL-31 was significantly overexpressed in pruritic atopic compared with nonpruritic psoriatic skin inflammation. Highest IL-31 levels were detected in prurigo nodularis, one of the most pruritic forms of chronic skin inflammation. In vivo, staphylococcal superantigen rapidly induced IL-31 expression in atopic individuals. In vitro, staphylococcal enterotoxin B but not viruses or T(H)1 and T(H)2 cytokines induced IL-31 in leukocytes. In patients with atopic dermatitis, activated leukocytes expressed significantly higher IL-31 levels compared with control subjects. IL-31 receptor A showed most abundant expression in dorsal root ganglia representing the site where the cell bodies of cutaneous sensory neurons reside.

CONCLUSION

Our findings provide a new link among staphylococcal colonization, subsequent T-cell recruitment/activation, and pruritus induction in patients with atopic dermatitis. Taken together, these findings show that IL-31 may represent a novel target for antipruritic drug development.

Prurigo nodularis: Epidemiology and clinical features

Prurigo nodularis (PN) is a chronic inflammatory skin disease characterized by intensely pruritic, hyperkeratotic nodules that favor the extensor surfaces of the extremities and the trunk. In addition to its significant impact on quality of life, many patients with PN are recalcitrant to therapy because there are currently no therapies approved by the US Food and Drug Administration. In the first article of this 2-part continuing medical education series, we describe the broader epidemiology, patient demographics, physical examination findings, and symptoms to aid in the timely recognition and diagnosis of PN. Furthermore, we quantify the burden of comorbidities in PN by discussing the broad spectrum of systemic diseases and mental health conditions that have been associated with this condition. The second article of this 2-part series focuses on the pathogenesis of PN and provides detailed algorithms for comprehensive work-up and management.

Diagnosis and treatment of actinic prurigo

Actinic prurigo (AP) is an idiopathic photodermatosis that affects mainly the mestizo population in Latin America. It has an early onset, a slight predominance in women, and affects the sun-exposed areas of the skin, causing erythematous papules and lichenified plaques secondary to intense and chronic pruritus. Lesions can be induced by both ultraviolet A (UVA) and ultraviolet B (UVB). An association with several human leukocyte antigen (HLA) alleles has been reported. AP is unique among all photodermatoses in its remarkable response to thalidomide. In the past the microscopic features of AP have been considered as nonspecific; however, the constant finding of dense lymphocytic inflammatory infiltrates and the immunogenetic features of AP support the existence of an immunologic mechanism in its pathogenesis.

Prurigo Nodularis Is Characterized by Systemic and Cutaneous T Helper 22 Immune Polarization

Prurigo nodularis (PN) is an understudied, chronic inflammatory skin disease that disproportionately affects African Americans and presents with intensely pruritic nodules of unknown etiology. To better characterize the immune dysregulation in PN, PBMCs and skin biopsies were obtained from patients with PN and healthy subjects (majority African American) matched by age, race, and sex. Flow cytometric analysis of functional T-cell response comparing patients with PN with healthy subjects identified increased γδT cells (CD3+CD4-CD8-γδTCR+) and Vδ2+ γδT enrichment. Activated T cells demonstrated uniquely increased IL-22 cytokine expression in patients with PN compared with healthy controls. CD4+ and CD8+ T cells were identified as the source of increased circulating IL-22. Consistent with these findings, RNA sequencing of lesional PN skin compared with nonlesional PN skin and biopsy site‒matched control skin demonstrated robust upregulation of T helper (Th) 22‒related genes and signaling networks implicated in impaired epidermal differentiation. Th22‒related cytokine upregulation remained significant, with stratifications by race and biopsy site. Importantly, the expression of the IL-22 receptors IL22RA1 and IL22RA2 was significantly elevated in lesional PN skin. These results indicate that both systemic and cutaneous immune responses in patients with PN are skewed toward a Th22/IL-22 profile. PN may benefit from immunomodulatory therapies directed at Th22‒mediated inflammation.

HLA typing in actinic prurigo

Thirty-two actinic prurigo patients of Cree ancestry underwent human lymphocyte antigen (HLA) typing and were compared with 32 control subjects of Cree ancestry. We found a significantly increased frequency of HLA-A24 and Cw4 antigens and a significant decrease in the frequency of the A3 antigen in actinic prurigo patients. These HLA associations may be helpful in determining whether actinic prurigo is a distinct disease or a variant of polymorphous light eruption.

HLA-DR4 may determine expression of actinic prurigo in British patients

Human leukocyte antigen (HLA) associations have been reported in Amerindian patients with actinic prurigo. To determine if similar associations are present in the British Caucasoid population with actinic prurigo, 26 patients underwent serological typing for HLC Class I and II antigens. DNA analysis by both sequence-specific priming and group-specific amplification with single-stranded oligonucleotide probe hybridization was used to confirm the DR and DQ typing and to perform DR4 subtyping. All patients were DR4 positive, and 25 of 26 patients were DQ7 positive. DR4 subtyping revealed 12 of 20 patients tested to be DRB1*0407. A nonsignificant association was also found with HLA B55 that is in linkage disequilibrium with DRB1*0407. No HLA associations were found in 25 British Caucasoid patients with polymorphic light eruption. DRB1*0407 is rare in European Caucasoids without actinic prurigo, and HLA-DR4 may have an important role in determining expression of this disease.

Actinic prurigo among the Chimila Indians in Colombia: HLA studies

The Chimila, a Colombian Amerindian group that lives at a low altitude, have a high incidence of actinic prurigo. We present the human lymphocyte antigen (HLA) findings of 43 Chimilas with the disease and of 62 control subjects and show an association of actinic prurigo with the Cw4 antigen.

The specific dermatoses of pregnancy: a re-appraisal

Pregnancy is associated with immunological, endocrine, metabolic and vascular changes that may adversely affect the skin. The specific dermatoses of pregnancy are disease entities almost exclusively related to the pregnancy or the puerperium.

LEARNING OBJECTIVE

At the conclusion of this learning activity, participants should be aware of the main entities of the specific pregnancy dermatoses, their clinical presentations, the main diagnostic criteria and therapeutic options.

Proliferating cell nuclear antigen (PCNA) in common epidermal lesions.. An immunohistochemical study of proliferating cell populations

A commercially available antibody to proliferating cell nuclear antigen was used to characterize and compare proliferating cell populations in paraffin sections of benign, premalignant, and malignant lesions of human epidermis using routine immunohistochemical techniques. Three patterns emerged. An ordered pattern was found in prurigo nodularis and keratoacanthoma, wherein moderately and strongly positive nuclei were distributed in a continuous, basal-suprabasal layer of relatively uniform thickness. There was graded loss and ultimate extinction of PCNA staining in progressively more superficial epidermal cells. A basal dysplastic pattern was found in actinic keratosis and squamous cell carcinoma. Nuclei of essentially all dysplastic cells of both categories expressed PCNA, with a preponderance of strongly positive nuclei. These were localized to basal-suprabasal zones that were often expanded. Loss of PCNA reactivity toward the surface was often abrupt. Bowen's disease exhibited a diffuse dysplastic pattern, wherein large numbers of moderately and strongly positive nuclei, in random array, were present in essentially full thickness distribution. In many fields, however, a layer of cytologically bland basal cells, with faint or no nuclear staining, was interposed between dysplastic epithelium and dermis. This study has demonstrated that proliferating cell populations in epidermal lesions can be assessed with simple, inexpensive methods. There were consistent differences between the proliferating cell populations of the various entities studied, differences that can be reasonably correlated with other known clinical, microscopic, and biologic features of the lesions. This technique should provide an interesting new avenue for study of diverse cutaneous diseases.

Further evidence of the role of HLA-DR4 in the genetic susceptibility to actinic prurigo

BACKGROUND

Actinic prurigo (AP) is triggered by sun exposure. Its prevalence in Mexicans seems to be particularly high, which suggests a genetic susceptibility.

OBJECTIVE

Our purpose was to determine the role of major histocompatibility complex (MHC) genes in the genetic susceptibility to AP.

METHODS

Fifty-six Mexican Mestizo patients with AP underwent serologic typing for HLA class I and class II antigens. Class II MHC genes were also studied by DNA analysis. Findings in patients were compared with 100 ethnically matched healthy controls.

RESULTS

We found that 92.8% of patients with AP were HLA-DR4 positive (corrected p = 0.002; odds ratio [OR] = 10.1). The class I antigens HLA-A28 and HLA-B39 (B16) were also significantly increased (p < or = 0.000001, OR = 20.9 and p = 0.0001, OR = 6.7, respectively) compared with normal controls. Allele-specific oligonucleotide DR4 subtyping showed that 80.7% of HLA-DR4+ patients with AP were also positive for the DRB1*0407 allele.

CONCLUSION

These results confirm the role of HLA-DR4 (DRB1*0407) in the genetic susceptibility to AP and raise the possibility of a role for class I MHC antigens HLA-A28 and B16 in Mexican patients.

Aprepitant in Anti-histamine-refractory Chronic Nodular Prurigo: A Multicentre, Randomized, Double-blind, Placebo-controlled, Cross-over, Phase-II trial (APREPRU)

The aim of this multicentre, randomized, double-blind, placebo-controlled, cross-over, phase-II study was to determine the antipruritic effect of aprepitant vs. placebo in 58 patients with anti-histamine-refractory chronic pruritus in chronic nodular prurigo. Patients were randomized to receive either first oral aprepitant 80 mg/day or placebo for 4 weeks. Following a 2-week wash-out phase, the patients were crossed-over to receive the other treatment for 4 weeks. Primary efficacy criterion was the intra-individual difference between mean itch intensity (visual analogue scale) at baseline compared with the end of treatment period. Prurigo lesions, pruritus course, quality of life, patient benefits, and safety were secondary parameters. No significant differences were found between aprepitant treatment and placebo for any of the parameters investigated. Under the experimental conditions of the study, aprepitant, 80 mg daily for 4 weeks, did not have an antipruritic effect in patients with chronic prurigo. (DRKS00005594; EudraCT Number: 2013-001601-85).

Effectors of inflammation in actinic prurigo

BACKGROUND

Actinic prurigo is a specific familial photodermatosis of uncertain pathogenesis.

OBJECTIVE

Our purpose was to investigate the immunohistologic presentation of actinic prurigo to explore the involved pathomechanisms.

METHODS

The present immunohistochemical study was performed on biopsy specimens from 20 Mexican patients presenting with a severe and perennial form of the disease.

RESULTS

The dense inflammatory infiltrate was composed predominantly of helper T type 1 lymphocytes admixed with scattered B-cell lymphoid follicles and numerous dermal dendrocytes. Keratinocytes contained abundant tumor necrosis factor-alpha and calprotectin.

CONCLUSION

In subjects genetically predisposed to actinic prurigo, ultraviolet light may trigger excessive tumor necrosis factor-alpha production by keratinocytes whose sustained release in turn exerts its proinflammatory activity and deleterious epidermal effects. Such a cascade of events is in line with the therapeutic benefit already reported when thalidomide is used to treat actinic prurigo.

Calcitonin gene-related peptide immunoreactivity in prurigo nodularis: a comparative study with neurodermatitis circumscripta

Eight patients with intensely pruritic lesions of chronic idiopathic prurigo nodularis and three patients with neurodermatitis circumscripta were investigated using the indirect immunofluorescence method. Results showed similarities in epidermal hyperplasia but not in nerve proliferation and neuropeptide immunoreactivity. Increased numbers of calcitonin gene-related peptide (CGRP) and substance P immunoreactive nerve fibre bundles were detected in specimens taken from prurigo nodularis lesions, but no increased immunoreactivity could be seen in specimens taken from patients having neurodermatitis circumscripta compared to normal skin. The neuropeptides, CGRP and substance P, may be responsible for the intense itching of prurigo nodularis lesions.

Immunologically mediated photodermatoses: diagnosis and treatment

Electromagnetic radiation may cause distinct skin conditions. The immunologically mediated photodermatoses (IMP, previous term: idiopathic photodermatoses) represent a heterogenous group of disorders presenting with pathologic skin reactions caused by optical radiation, particularly in the UVA wavelength region. The exact pathomechanism in IMP remains to be elucidated; however, it is very likely (auto)-immunologic in nature. Polymorphic light eruption, actinic prurigo, hydroa vacciniforme, chronic actinic dermatitis, and solar urticaria are the most important conditions that may be summarized under the term IMP. IMP frequently result in a significant reduction in quality of life in affected individuals, mainly because of troublesome symptoms such as intractable itch and pain. Photodiagnostic procedures are mandatory for the exact determination of action spectra and the degree of photosensitivity. Broad-spectrum photoprotection is essential in the prevention of IMP. Photo(chemo)therapeutic regimens are predominantly used to increase the cutaneous immunologic tolerance against ambient UV radiation. In severe forms of IMP, immunomodulatory and immunosuppressive therapies may need to be considered. Overall, IMP form a significant group of skin conditions that can be extremely disabling to the patient and are difficult to diagnose and treat.

HLA typing in polymorphous light eruption

Human leukocyte antigen typing of 41 white patients with polymorphous light eruption (limited concept) showed no significant differences when compared with the typing of 51 white control subjects. We previously found that actinic prurigo, an idiopathic photodermatosis particularly associated with Amerindians, has a positive association with antigens A24 and Cw4 and a negative association with A3. We suggest, on the basis of both laboratory and clinical findings, that polymorphous light eruption (limited concept) and actinic prurigo are two different and distinct diseases.

Lymphocyte subtypes and adhesion molecules in actinic prurigo: observations with cyclosporin A

BACKGROUND

Actinic prurigo is a photodermatitis in which UV light is implicated by an unknown mechanism.

METHODS

Skin biopsies of 19 patients with actinic prurigo and 11 controls were analyzed by immunohistochemistry.

RESULTS

In actinic prurigo patients, there was a significant increase in the number of CD3, CD4, CD8, CD45RA, CD45RO, and CD45RB lymphocytes and Langerhans cells, as well as in the level of human leukocyte antigen-DR (HLA-DR) expression and cell adhesion molecules lymphocyte functional antigen-1 (LFA-1), intercellular adhesion molecule-1 (ICAM-1), and endothelial leukocyte adhesion molecule-1 (ELAM-1). Actinic prurigo patients were treated with cyclosporin A (CsA), and a final skin biopsy was taken after 6 months of treatment. All the cell populations and markers studied, except for the CD4 lymphocytes, Langerhans cells, and HLA-DR expression, returned to normal levels.

CONCLUSIONS

CsA was found to be effective in relieving the clinical symptoms of actinic prurigo.

Actinic prurigo: Clinical features and HLA associations in a Canadian Inuit population

BACKGROUND

Actinic prurigo (AP) is an idiopathic familial photodermatitis. AP of the Inuit is rarely reported and poorly characterized.

OBJECTIVE

Our purpose was to examine the clinical features and HLA associations of AP in an Inuit population.

METHODS

Thirty-seven Inuit subjects with AP were administered a questionnaire and underwent a cutaneous examination. Other causes of photosensitivity were excluded. HLA class I typing was performed by polymerase chain reaction and sequence-specific primers and class II typing by polymerase chain reaction and sequence-specific oligonucleotide probes.

RESULTS

Subjects were 81.1% female, 67.6% had a family history of photosensitivity, and all experienced seasonal variation. The average age at onset of photosensitivity was 29 years, and only 27% had a trend toward improvement in photosensitivity. Involvement of eyes and nonexposed skin was reported in 62.2% and 18.9% of subjects, respectively. Physical examination revealed involvement of the face (64.9%), lip (32.4%), ear (13.5%), and dorsal aspect of the hand (24.3%). HLA-DRB1*14 was present in 51.2% of subjects and 26.2% of controls (P =.022, odds ratio = 2.975). This is a previously unreported HLA association.

CONCLUSION

AP in the Inuit is a seasonal, pruritic photodermatitis, often commencing in adulthood and worsening over time. A novel association with HLA-DRB1*14 has been discovered. Overall, this novel HLA association, the absence of HLA associations previously reported in non-Inuit populations, and clinical distinguishing features support the concept that AP in the Inuit may have a distinct immunopathogenic basis that translates into a different phenotype. It also raises the question of whether AP in the Inuit is a distinct photosensitivity disorder specific to this group that has been genetically isolated because of geographic and cultural seclusion.

Prurigo pigmentosa: role of ICAM-1 in the localization of the eruption

Immunohistochemical studies were carried out on the skin lesions of two cases of prurigo pigmentosa. There was a predominance of CD4+ cells in the dermal infiltrate, whereas those lymphocytes in the epidermis were mainly CD8+ cells. The majority of dermal and epidermotropic lymphocytes showed an intense expression of lymphocyte function-associated antigen 1 (LFA-1). The number of CD1+ cells was increased in the epidermis. There was intense expression of ICAM-1 by keratinocytes in the erythematous papules. Focal expression of ICAM-1 was still observed in the residual pigmented areas and could explain the recurrence of the lesions at these sites.

Immunofluorescent patterns in the skin in Besnier's prurigo. The eczema asthma syndrome

The immunofluorescent patterns in the skin of eighteen patients with Besnier's prurigo were studied at different stages of eczematous lesions. The presence, distribution pattern, and numbers of immunoglobulin and complement-positive lymphocytes in twenty-nine biopsies are reported. In all cases IgE-positive lymphocytes were present in both clinically uninvolved and involved skin. IgG, IgM and IgE-positive lymphocytes showed a characteristic distribution pattern in the dermis. In the acute stages IgM deposition was prominent in the basement membrane zone and it is suggested that damage to the basement membrane results in diffusion of immunoglobulin and complement into the epidermis. These features were not present in a control group of normal skin and of other dermatoses.

Patch testing in prurigo nodularis

32 patients with prurigo nodularis evaluated at the Mayo Clinic from 1975 to 1987 have been patch tested for sensitivity to appropriate allergen series; 25 of these had relevant positive reactions and subsequent follow-up to 5 to 14 years was available for 11. 6 patients had persistent disease and 5 had resolution or marked improvement. 3 of these latter patients noted a strong positive correlation between improvement and avoidance of contact allergens. Screening for contact sensitivity may be helpful in the management of this refractory dermatosis, particularly if there is a coexistent dermatitis.

Evidence that thalidomide modifies the immune response of patients suffering from actinic prurigo

BACKGROUND

Actinic prurigo (AP) is a photodermatosis with a restricted ethnic distribution, mainly affecting Mestizo women (mixed Indian and European). The lesions are polymorphic and include macules, papules, crusts, hyperpigmentation and lichenification. Thalidomide, an effective immunomodulatory drug, was first used successfully to treat AP in 1973. In this work we describe the effect that thalidomide had on TNF-alpha sera levels and on IL-4- and IFN gamma (IFNgamma)-producing lymphocytes of actinic prurigo (AP) patients.

METHODS

Actinic prurigo patients were analyzed before and after thalidomide treatment. The percentage of IL-4+ or IFNgamma+ CD3+ lymphocytes was analyzed in eight of them by flow cytometry. TNFalpha in sera was measured by ELISA in 11 patients.

RESULTS

A direct correlation was observed between resolution of AP lesions and an increase in IFNgamma+ CD3+ peripheral blood mononuclear cells (P < or = 0.001) and a decrease in TNFalpha serum levels (no statistical difference). No IL-4+ CD3+ cells were detected.

CONCLUSIONS

Our findings confirm that AP is a disease that has an immunological component and that thalidomide clinical efficacy is exerted not only through inhibition of TNFalpha synthesis, but also through modulation of INFgamma-producing CD3+ cells. These cells could be used as clinical markers for recovery.