A non-HLA gene within the MHC in psoriasis.
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Genes, MHC Class I↗
Biomedical subjects
J N Barker
Publications and source records attributed to J N Barker.
Increased T-cell receptor vbeta2 chain expression in skin homing lymphocytes in psoriasis.
Studies have shown over-representation of certain T-cell receptor (TCR) Vbeta chains in lesional psoriatic skin, implying selection or expansion, possibly by bacterial superantigen. We investigated the pattern of TCR Vbeta chain usage in peripheral blood lymphocytes (PBL) bearing the skin homing receptor cutaneous lymphocyte associated antigen (CLA) in psoriasis patients. Results showed increased expression of TCR Vbeta2 in CLA-positive PBL in psoriasis patients (n = 15) compared with normals (n = 10); P < 0.002. As Vbeta2 is preferentially expressed by lymphocytes responding to certain bacterial superantigens, this study could possibly indicate a role for superantigens in the pathogenesis of psoriasis.
Adult↗
Topical maxacalcitol for the treatment of psoriasis vulgaris: a placebo-controlled, double-blind, dose-finding study with active comparator.
1alpha, 25-Dihydroxy-22-oxacalcitriol (maxacalcitol) is a vitamin D3 analogue which displays approximately 10 times greater efficacy at suppressing keratinocyte proliferation in vitro than calcipotriol and tacalcitol. To determine clinical efficacy, a phase II double-blind, randomized, left vs. right, concentration-response study was performed with once-daily topical maxacalcitol in patients with mild to moderate chronic plaque psoriasis. Primary efficacy parameters were psoriasis severity index (PSI) based on sum of scores for erythema, scaling and induration and investigators' overall assessment of patients' response to therapy at 8 weeks of treatment. One hundred and forty-four patients participated. All concentrations of maxacalcitol ointment (6, 12.5, 25 and 50 microg/g) were significantly more effective at reducing PSI than placebo (P < 0.01), with greatest effect noted for maxacalcitol 25 microg/g. Calcipotriol ointment 50 microg/g once daily as active comparator had a similar effect. Marked improvement or clearance of psoriasis was greatest for maxacalcitol 25 microg/g (55% of subjects) which compared favourably with calcipotriol (46%). Improvement continued throughout the study period, with no plateau at week 8. Investigators' and patients' side preference (secondary efficacy parameters) rated maxacalcitol more effective than placebo and 25 microg/g maxacalcitol better than calcipotriol (P < 0.05 for investigators' assessment). Twelve patients withdrew from the study due to adverse events, of which four were judged to be due to study medication. This study indicates that once-daily maxacalcitol ointment is effective in the management of plaque psoriasis, with greatest effect noted at 25 microg/g. As no response plateau was noted at 8 weeks, these data suggest that further benefit might be obtained if maxacalcitol ointment were applied for longer. Finally, investigators' overall assessment and side preference suggest that maxacalcitol 25 microg/g may be more effective than once-daily calcipotriol.
Administration, Topical↗
Combination treatment with methotrexate and cyclosporin for severe recalcitrant psoriasis.
An increasingly important approach to the management of patients with severe psoriasis is the concurrent use of two systemic treatments. Previous guidelines have advised against the use of methotrexate and cyclosporin in combination. We report the successful use of a combination of methotrexate and cyclosporin in the treatment of 19 patients with severe, recalcitrant psoriasis, 15 of whom had psoriatic arthropathy. Most patients had previously received two or more systemic treatments. Before combination treatment was started nine of the patients were taking methotrexate and 10 were taking cyclosporin at the maximum tolerated doses. The duration of combination treatment was bimodally distributed, with seven patients having short-term treatment (mean +/- SD duration 18. 9 +/- 15.7 weeks) and 12 patients having long-term treatment (mean +/- SD duration 193.2 +/- 160.6 weeks). Those patients who received short-term treatment did not develop any evidence of toxicity from either agent. Of those patients on long-term treatment, three developed mild impairment of renal function that returned to normal following a reduction in dose of cyclosporin, and three had impairment of renal function (following long-term cyclosporin monotherapy) that improved, but did not normalize, following a reduction in dose of cyclosporin. In each case, combination treatment for psoriasis resulted in good control of both skin and joint problems using lower doses of each agent than would have been used for monotherapy. We conclude that the combination of methotrexate and cyclosporin is an effective treatment for this group of patients.
Adult↗
Bullous pemphigoid developing during systemic therapy with chloroquine.
Bullous pemphigoid has been reported to be induced or precipitated by systemic therapy with several drugs, including penicillamine, captopril, frusemide and ampicillin. We report an African male patient with sarcoidosis who was prescribed chloroquine for progressive dyspnoea. After 3 months he developed generalized pruritus which evolved into a widespread bullous eruption with acral targetoid lesions resembling erythema multiforme. The histological and immunofluorescence findings were diagnostic of bullous pemphigoid. The atypical clinical features of this case resemble the phenotype that has been noted in previous reports of drug-induced bullous pemphigoid.
Antirheumatic Agents↗
In vivo UVA-1 and UVB irradiation differentially perturbs the antigen-presenting function of human epidermal Langerhans cells.
Ultraviolet B (UVB, 290-320 nm) radiation is known to suppress the immune function of epidermal Langerhans cells. We have recently described that in vitro UVB irradiation perturbs the antigen-presenting cell function of Langerhans cells by inhibiting their expression of functional B7 costimulatory molecules (B7-1, B7-2). The aim of this study was to determine wavelength-specific UV effects on Langerhans cells function in vivo, specifically UVB and UVA-1. To address this issue, volunteers were irradiated on the sun protected volar aspects of their forearms with 3 x minimal erythema dose of UVB (Philips TL-12) and UVA-1 (UVASUN 5000 Mutzhaas). Langerhans cells were isolated from suction blister roofs immediately following irradiation. Langerhans cells isolated from UVB- but not from UVA-1-irradiated skin failed to activate naïve resting allogeneic T cells (mixed epidermal cell leukocyte reaction) or primed tetanus toxoid reactive autologous T cells. Langerhans cells isolated from sham-irradiated or UVA-1-irradiated skin strongly upregulated B7-2 molecules during short-term tissue culture. By contrast, Langerhans cells from UVB-irradiated skin did not upregulate B7-2 molecules. Furthermore, exogenous stimulation of the B7 pathway by anti-CD28 stimulatory monoclonal antibodies restored the capacity of UVB-irradiated Langerhans cells to activate both alloreactive and tetanus toxoid-reactive T cells, implying suppressed antigen-presenting cell activities and perturbed B7 expression of Langerhans cells isolated from UVB-irradiated skin are related. Those studies demonstrate that in vivo UVB, but not UVA-1, interferes with the activation-dependent upregulation of B7 molecules on Langerhans cells, which in turn is of functional relevance for the perturbed antigen-presenting cell function of Langerhans cells within UVB- but not UVA-1-irradiated skin.
Antigen Presentation↗
Characterization of the major susceptibility region for psoriasis at chromosome 6p21.3.
Psoriasis is a common inflammatory skin condition caused by genetic and environmental factors. Recent genome-wide linkage analyses have identified a locus encoding susceptibility to psoriasis and placed this gene in the 12 cM interval between markers D6S426 and D6S276 on chromosome 6p21.3. This is a broad region and encompasses the human major histocompatibility complex. We have sought to localize the susceptibility gene more precisely by exploiting the linkage, haplotype, and linkage disequilibrium information available through genotyping 118 affected sib pairs, their parents and other affected family members. A total of 14 highly polymorphic markers were genotyped, combining anonymous loci with the class I genes HLA-B and -C distributed across a genetic interval of approximately 14 cM including the entire major histocompatibility complex. Through the application of higher density mapping within the major histocompatibility complex, we identified those regions most commonly shared identical by descent in patients with psoriasis. Using the transmission-disequilibrium test, we found significant evidence of linkage and allelic association across an interval defined by the markers tn62 (p = 1.0 x 10(-7)), HLA-B (p = 4.0 x 10(-7)), and HLA-C (p = 2.7 x 10(-9)), a region encompassed within a 285 kb genomic DNA fragment. Hence these studies contribute to the refinement of the localization of a major psoriasis susceptibility gene and place the critical region near to HLA-C.
Adolescent↗
Optimising the use of tazarotene in clinical practice: consensus statement from the European advisory panel for tazarotene (Zorac TM).
BACKGROUND: This paper reports the proceedings of the European Advisory Panel Meeting for tazarotene (Zoractrade mark), which took place in Cologne on May 7, 1998. AIM: The aim of this meeting was to discuss recommendations for the use of tazarotene based on the clinical data available and on the clinical experience of the Advisory Panel members, and to identify future research needs. RECOMMENDATIONS: Based on currently available data, tazarotene can be used for the treatment of chronic, stable, plaque-type psoriasis, on the trunk or limbs covering up to 20% of the body surface area. In clinical trials, patients generally experienced a clinical response within 4 weeks of starting tazarotene treatment, and improvement was maintained for up to 12 weeks after stopping therapy. Results from published and not yet published clinical trials show that the efficacy and tolerability of tazarotene can be enhanced by the addition of topical corticosteroids to the treatment regimen and that, when used in combination with broad-band UVB phototherapy, tazarotene reduces the amount of UV light required to treat plaques. Tazarotene gel is available in two concentrations, 0.05 and 0.1%. The Advisory Panel recommends that the choice of concentration should be based on factors such as the irritability of the patient's skin and the thickness of plaques. Irritation can be managed by reducing the concentration or frequency of application, or by adding a topical corticosteroid to therapy. Tazarotene shows promise as a treatment for psoriasis in special localisations, such as the scalp, face and skin folds, although clinical studies are required.
Humans↗
Contrasting effects of ultraviolet A1 and ultraviolet B exposure on the induction of tumour necrosis factor-alpha in human skin.
Ultraviolet B (UVB) irradiation of the skin causes immunosuppression which is relevant to the induction of skin cancer. The mechanism of this immunomodulation is unclear but various regulatory molecules have been implicated, including cis-urocanic acid (cis-UCA) and the cytokines tumour necrosis factor-alpha (TNF-alpha) and interleukin 10 (IL-10). Whether ultraviolet A (UVA) induces similar changes has not been investigated fully. We studied the effect of in vivo UVB and long-wave UVA (UVA1) exposure on the induction of TNF-alpha, IL-10 and cis-UCA in human skin. Volunteers were irradiated with three minimal erythema doses (MED) of UVB or UVA1. At different times after irradiation, suction blisters were raised from irradiated and from non-irradiated (control) skin. The TNF-alpha and IL-10 protein concentration, and the percentage of cis-UCA in the blister fluid, were then determined. UVB irradiation of human skin led to a rapid and significant increase in TNF-alpha concentration in suction-blister fluid, with maximal values 6 h after irradiation (n = 6, P < 0.05). In contrast, UVA1 irradiation led to a decrease in TNF-alpha concentration in the suction-blister fluid compared with non-irradiated skin, with the lowest values 6 h after irradiation (n = 6, P < 0.05). Both UVB and UVA1 exposure of the skin induced a slight increase in IL-10 concentration. However, the increase in IL-10 was only significant after UVB irradiation (UVB, n = 6, P < 0.05; UVA, n = 7, P < 0.1). As previously shown, both UVB and UVA1 result in the photo-isomerization of trans-UCA and an increased percentage of cis-UCA was found in the suction-blister fluid. Thus the results show differential effects of UVB and UVA1 irradiation on the induction of immunoregulatory molecules, which may help to explain the variation in immune responses after UVB and UVA1 exposure of human skin.
Adult↗
Ultraviolet B induced suppression of induction of contact sensitivity in human skin is not associated with tumour necrosis factor-alpha-308 or interleukin-10 genetic polymorphisms.
Low doses of ultraviolet B (UVB) can induce localized immunosuppression in skin. This effect may be important in the induction of skin cancers and is thought to be mediated by tumour necrosis factor (TNF) alpha and interleukin (IL) 10 in conjunction with other factors. In humans a transition polymorphism in the TNF-alpha gene may affect TNF-alpha secretion and the promoter region of the IL-10 gene contains a CA repeat polymorphism which may affect gene function. We have therefore investigated the association of these polymorphisms with UVB-induced immunosuppression in humans. Volunteers (n = 42) were irradiated with UVB then sensitized on irradiated skin with diphenylcyclopropanone (DPCP) and subsequently antigen challenged with DPCP. DNA was extracted from blood samples and volunteers genotyped for the TNF-alpha polymorphism by polymerase chain reaction (PCR) and restriction digestion. The CA repeat polymorphism was amplified by PCR and sized by gel electrophoresis. Twenty-four volunteers were susceptible to UVB-induced immunosuppression and 18 were resistant. The association of allele frequencies and phenotype was statistically tested using a chi2-test. For both the TNF-alpha and IL-10 polymorphisms, there was no statistically significant association between allele types and response to UVB. These results indicate that variation in the immune response to UVB in humans is not associated with the TNF-alpha-308 transition or IL-10 CA repeat polymorphisms, although other as yet undetected DNA sequence variants of these genes may be involved.
Alleles↗
Effect of granulocyte macrophage-colony stimulating factor on Langerhans cells in normal and healthy atopic subjects.
Granulocyte macrophage-colony stimulating factor (GM-CSF) is a multipotent cytokine produced by many cutaneous cell types including keratinocytes. Langerhans cells (LC) represent the major antigen-presenting cells in skin, and in vitro studies demonstrate that GM-CSF is of pivotal importance in LC. Healthy volunteers (n = 3 non-atopic, n = 3 with atopy) received recombinant human GM-CSF (0. 05 microg/mL) by intradermal injection for 3 days to the same site. Diluent was injected in a similar manner as control. Biopsies were taken 24 h after the final injection and examined immunohistochemically for LC and inflammatory cell markers. Compared with control sites, intradermal GM-CSF resulted in shortening of dendritic cell processes and redistribution of LC in the epidermis; numbers of CD1a + cells in the epidermis were significantly decreased (P < 0.005), while those in the dermis were significantly increased (P < 0.05) following intradermal GM-CSF when compared with controls. Double labelling studies on epidermal CD1a + cells indicated de novo expression of intercellular adhesion molecule (ICAM)-1 and increased expression of HLA-DR following GM-CSF (P < 0. 005, P < 0.005, respectively). Additional findings included a marked mixed inflammatory cell infiltrate in the dermis and increased expression of the endothelial cell adhesion molecules E-selectin and ICAM-1. These data indicate that in normal human skin, GM-CSF induces changes in the phenotype and distribution of CD1a + cells consistent with LC functional maturation and exit from the epidermis to the dermis. As these events are central to the initiation of cutaneous inflammation, GM-CSF may potentially play a critical role in the pathogenesis of inflammatory dermatoses.
Adolescent↗
Pathogenesis of psoriasis.
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Genetic Predisposition to Disease↗
Susceptibility to effects of UVB irradiation on induction of contact sensitivity, relevance of number and function of Langerhans cells and epidermal macrophages.
Sensitization on skin exposed to acute low-dose UVB irradiation separates normal humans into two phenotypically distinct groups: One group, following sensitization on UVB-irradiated skin, develops contact sensitivity, designated UVB resistant (UVB-R) and the second group, following sensitization on UVB-irradiated skin, fails to develop contact sensitivity, designated UVB susceptible (UVB-S). To investigate whether UVB susceptibility in humans in related to antigen-presenting activity in the skin we studied the effect of UVB irradiation on the number and function of the epidermal antigen-presenting cells in volunteers identified as UVB-R and UVB-S. Single cell suspensions of epidermal cells from control skin and skin exposed to 3 minimal erythema doses (MED) of UVB 3 days previously were stained for Langerhans cells (CD1a+HLA-DR+) and epidermal macrophages (CD1a-HLA-DR+). The UVB exposure of the skin significantly decreased the percentage of Langerhans cells (UVB-R: n = 7, P < 0.02, UVB-S: n = 6, P < 0.03) and increased the percentage of epidermal macrophages (UVB-R: n = 7, P < 0.03, UVB-S: n = 6, P < 0.03) however to the same degree in both the UVB-R and the UVB-S group. To study the effect on Langerhans cell alloreactivity, epidermal cells were harvested immediately after UVB irradiation. However, in both UVB-R and UVB-S subjects the Langerhans cell alloreactivity was blocked to the same degree immediately after UVB irradiation compared to nonirradiated epidermal cells. To determine the effect of UVB irradiation on epidermal macrophages, epidermal cells were harvested 3 days after UVB irradiation. Irradiated epidermal cells from both UVB-R and UVB-S subjects demonstrated a strong antigen-presenting capacity compared to epidermal cells from control skin leading to activation of T cells that mainly secrete interferon (IFN)-gamma and not interleukin (IL)-4. In conclusion we found that UVB susceptibility was not correlated with the number of Langerhans cells or epidermal macrophages in the skin at the same time of sensitization. Neither was it correlated with the capacity of Langerhans cells nor UVB-induced epidermal macrophages to activate T cells in vitro.
Adult↗
Psoriasis as a T cell-mediated autoimmune disease.
Psoriasis is a common chronic skin disease in which T lymphocytes are thought to play a vital pathogenic role. Evidence shows that these are activated memory skin-homing T cells which induce characteristic disease features via cytokine production. Understanding the mechanisms of T cell accumulation in skin and mediation of psoriasis is critical to designing immunotherapy for this distressing disease.
Autoimmune Diseases↗
Progress in psoriasis. Psoriasis: from gene to clinic. London, UK, 5-7 December 1996.
In a meeting dedicated to a single common complex disease such as psoriasis, it is not surprising that many unanswered questions were raised. However, the meeting highlighted the impressive progress being made in psoriasis research at both the investigative and the therapeutic levels. A follow-up meeting is to take place in 1999, when further characterization of susceptibility gene loci should be available, together with data concerning the selective nature of disease-causing T cells and the antigens that trigger the disease. Identification of these critical factors should allow development of highly specific therapeutic agents, some of which are beginning to find their way into clinical development.
Cell Differentiation↗
Contrasting effects of ultraviolet-A and ultraviolet-B exposure on induction of contact sensitivity in human skin.
Ultraviolet-B (UVB), in addition to direct effects on DNA, induces immunological changes in the skin that predispose to the development of skin cancer. Whether ultraviolet-A (UVA) induces similar changes is unknown. This effect can be investigated in humans in vivo using epicutaneous antigens as a model of tumour antigens. Volunteers (n = 46) were randomly assigned to received no sensitization, sensitization with the allergen diphenylcyclopropenone (DPCP) on non-UV-exposed normal skin, or sensitization with DPCP on skin exposed to three minimal erythema doses (MED) of either UVA or UVB radiation 3 days before sensitization. Three weeks after sensitization all volunteers were challenged with five different concentrations of DPCP. The challenge reactions were scored clinically and the increase in skin thickness was measured using a micrometer. Sensitization on UVB-exposed skin reduced the immunization rate compared with sensitization on non-irradiated skin (P < 0.03) as previously described. In contrast, sensitization on skin exposed to three MED UVA radiation did not result in a decreased immunization rate compared with non-irradiated skin. These results indicate that in humans erythemagenic doses of UVA radiation do not reduce the immunization rates to epicutaneous allergens. Thus UVB and UVA irradiation have contrasting effects on cell-mediated immunity in humans. These findings may at least in part explain the less carcinogenic effect of UVA irradiation.
Adolescent↗
Identification of a major susceptibility locus on chromosome 6p and evidence for further disease loci revealed by a two stage genome-wide search in psoriasis.
Psoriasis is a common chronic inflammatory disorder of the skin. To further understand the pathogenesis of psoriasis we have chosen to investigate the molecular genetic basis of the disorder. We have used a two-stage approach to search the human genome for the location of genes conferring susceptibility to psoriasis, using a total of 106 affected sibling pairs identified from 68 independent families. As over a third of the extended kindreds included affected relatives besides siblings, in addition to an analysis of allele sharing between affected sibling pairs, a novel linkage strategy was applied that extracts full non-parametric information. Four principal regions of possible linkage were identified on chromosomes 2, 8, 20 (p <0.005) and markers from the MHC region at 6p21 (p <0.0000006) for which significant evidence of linkage disequilibrium was also observed (p <0.00002). Whilst data from limited case control associations exist to implicate the MHC, the results of this genome wide analysis demonstrate that, at least in the population studied, a gene or genes located within the MHC and close to the class 1 HLA loci, represent the major determinant of the genetic basis of psoriasis.
Chromosomes, Human, Pair 6↗