Contrasting patterns of streptococcal superantigen-induced T-cell proliferation in guttate vs. chronic plaque psoriasis

Etiopathogenesis of Psoriasis: Integration of Proposed Theories

Psoriasis is a chronic inflammatory disease characterized by squamous and erythematous plaques on the skin and the involvement of the immune system. Global prevalence for psoriasis has been reported around 1-3% with a higher incidence in adults and similar proportions between men and women. The risk factors associated with psoriasis are both extrinsic and intrinsic, out of which a polygenic predisposition is a highlight out of the latter. Psoriasis etiology is not yet fully described, but several hypothesis have been proposed: 1) the autoimmunity hypothesis is based on the over-expression of antimicrobial peptides such as LL-37, the proteins ADAMTSL5, K17, and hsp27, or lipids synthesized by the PLA2G4D enzyme, all of which may serve as autoantigens to promote the differentiation of autoreactive lymphocytes T and unleash a chronic inflammatory response; 2) dysbiosis of skin microbiota hypothesis in psoriasis has gained relevance due to the observations of a loss of diversity and the participation of pathogenic bacteria such as Streptococcus spp. or Staphylococcus spp. the fungi Malassezia spp. or Candida spp. and the virus HPV, HCV, or HIV in psoriatic plaques; 3) the oxidative stress hypothesis, the most recent one, describes that the cell injury and the release of proinflammatory mediators and antimicrobial peptides that leads to activate of the Th1/Th17 axis observed in psoriasis is caused by a higher release of reactive oxygen species and the imbalance between oxidant and antioxidant mechanisms. This review aims to describe the mechanisms involved in the three hypotheses on the etiopathogeneses of psoriasis.

Childhood guttate psoriasis: an updated review

Background

Guttate psoriasis is common and affects 0.5-2% of individuals in the paediatric age group. This review aims to familiarize physicians with the clinical manifestations, evaluation, diagnosis and proper management of guttate psoriasis.

Methods

A search was conducted in July 2023 in PubMed Clinical Queries using the key term "guttate psoriasis". The search strategy included all observational studies, clinical trials and reviews published within the past 10 years. The information retrieved from the search was used in the compilation of the present article.

Results

Guttate psoriasis typically presents with an abrupt onset of numerous, small, scattered, tear-drop-shaped, scaly, erythematous, pruritic papules and plaques. Sites of predilection include the trunk and proximal extremities. There may be a history of preceding streptococcal infection. Koebner phenomenon is characteristic. Guttate psoriasis may spontaneously remit within 3-4 months with no residual scarring, may intermittently recur and, in 40-50% of cases, may persist and progress to chronic plaque psoriasis. Given the possibility for spontaneous remission within several months, active treatment may not be necessary except for cosmetic purposes or because of pruritus. On the other hand, given the high rates of persistence of guttate psoriasis and progression to chronic plaque psoriasis, some authors suggest active treatment of this condition.

Conclusion

Various treatment options are available for guttate psoriasis. Triggering and exacerbating factors should be avoided if possible. Topical corticosteroids alone or in combination with other topical agents (e.g. tazarotene and vitamin D analogues) are the most rapid and efficient treatment for guttate psoriasis and are therefore the first-line treatment for mild cases. Other topical therapies include vitamin D analogues, calcineurin inhibitors, anthralin, coal tar and tazarotene. Ultraviolet phototherapy is the first-line therapy for moderate-to-severe guttate psoriasis, as it is more practical than topical therapy when treating widespread or numerous small lesions. Systemic immunosuppressive and immunomodulatory therapies (e.g. methotrexate, cyclosporine, retinoids, fumaric acid esters and biologics) may be considered for patients with moderate-to-severe guttate psoriasis who fail to respond to phototherapy and topical therapies.

Intranasal streptococcal infection exacerbates psoriasis-like dermatitis via the induction of skin tissue-resident memory T cells

Recurrent streptococcal tonsillitis exacerbates psoriasis. Studies have indicated that T cells responding to streptococcal antigens in the skin are involved in the pathogenesis of the disease. However, a direct link between streptococcal tonsillitis and psoriasis has not been evidenced. In the present study, the impact of intranasal (i.n.) streptococcal infection on psoriasis was investigated using the imiquimod (IMQ) psoriasis mouse model. The results showed that repeated i.n. infection with group A Streptococcus (GAS) induced a robust and persistent Th17 response in the nasal-associated lymphoid tissue (NALT) and exacerbated IMQ-mediated psoriatic skin lesions. ELISpot and flow cytometry analyses revealed that GAS-reactive tissue-resident memory T cells (T_RM) were present in the skin of GAS-infected mice and produced IL-17/IL-23 axis cytokines in response to IMQ, compared to mice uninfected with GAS. In addition, i.n. infection with Streptococcus pneumoniae (Sp), a pathogen not associated with the development of psoriasis, also induced a persistent Th17 response in NALT but did not exacerbate IMQ-induced psoriatic inflammation nor elicited Sp-specific T cells in the skin. The results provide in vivo evidence that GAS-associated psoriasis is dependent on the skin GAS-specific T_RM cells induced by GAS nasopharyngeal infection and can be later activated by environmental triggers, leading to psoriatic inflammation. Reducing the reservoir of Th17 cells, which are source of skin T_RM cells, may constitute a promising treatment for psoriasis.

Factors Associated with Multi-Biologic Use in Psoriasis Patients at an Academic Medical Center and Review of Biologic Survival

Background

Despite their impressive efficacy in phase 3 trials, biologic agents for psoriasis (PsO) may lose efficacy over time. The factors associated with loss of efficacy have yet to be fully elucidated.

Objective

We aimed to identify factors associated with PsO patients using multiple biologics in comparison to patients who used 1 biologic. We also reviewed the literature comparing the survival of different biologic agents for PsO.

Methods

We examined clinical data from 222 psoriasis patients at the University of California San Francisco, of whom 51 reported use of 3 or more biologics and of whom 171 reported use of only a single biologic agent at the time of enrollment into a research database from 2006-2020. This study was IRB-approved at UCSF (#10-02830) and all subjects provided written informed consent. We performed univariate and multivariate regression analysis to identify significant demographic features, clinical features, and co-morbidities associated with multi-biologic use. We performed a literature review of studies comparing psoriasis biologic survival at 1, 2, and 5 years and factors associated with single biologic failure.

Results

In univariate analysis, duration of PsO, initial presentation of PsO on the gluteal cleft, erythrodermic psoriasis, and acne were associated with using 3 or more biologics. In multivariate analysis, duration of PsO, erythrodermic psoriasis, and acne remained significant. Our review of biologic survival revealed differences according to biologic class.

Conclusion

We identified novel factors associated with multi-biologic use in PsO. Further studies in this area are needed to achieve a precision medicine approach.

Keratin 17 in psoriasis: Current understanding and future perspectives

Keratin 17 (K17) is a multifaceted cytoskeletal protein that is not commonly expressed in the epidermis under normal physiological conditions. However, in psoriasis, K17 is overexpressed in the suprabasal layer of the epidermis and plays an important role in the pathogenesis of the disease. In this review, we have summarized our findings and those reported in other studies concerning the pathogenic functions of K17, as well as the mechanisms underlying the increase in K17 expression in psoriasis. K17 exerts both pro-proliferative and pro-inflammatory effects on keratinocytes. Moreover, K17 peptides trigger autoreactive T cells and promote psoriasis-related cytokine production. In turn, these cytokines modulate the expression, stability, and protein-protein interactions of K17 through transcriptional and translational regulation and post-translational modification of K17 in keratinocytes. Thus, a K17/T-cell/cytokine autoimmune loop is implicated in the pathogenesis of psoriasis, which is supported by the fact that therapies targeting K17 have achieved good outcomes in psoriasis-like mouse models. Future perspectives of K17 in psoriasis have also been discussed to provide potential directions for further studies.

Psoriasis: Embarking a dynamic shift in the skin microbiota

Recent interest has arisen regarding the role of microbiome and its composition in the pathogenesis of psoriasis. Numerous studies have shown that there are alterations in skin flora arrangement between normal individuals and psoriatic patients. Psoriasis exacerbation could be interconnected with epidermal or mucosal colonization with streptococci, Malassezia, Staphylococcus aureus, or Candida albicans. The role of cutaneous and gut microbiome in psoriasis pathogenesis has recently been studied in both human and animal models. In this review, we try to evaluate various pathogenic mechanisms linking the microbiota and psoriasis. The literature research included peer-reviewed articles which included clinical trials, original reports, and scientific reviews. MEDLINE and PubMed databases were searched from January 1990 to March 2021, including the reference lists of articles meeting our criteria.

Evidence linking atopy and staphylococcal superantigens to the pathogenesis of lymphomatoid papulosis, a recurrent CD30+ cutaneous lymphoproliferative disorder

Background

Primary cutaneous CD30+ lymphoproliferative disorders (CD30CLPD) are the second most common type of cutaneous T cell lymphoma (CTCL) and include lymphomatoid papulosis (LyP) and primary cutaneous anaplastic large cell lymphoma (pcALCL). Case reports and small patient series suggest an association of CD30CLPD with atopic disorders. However, the prevalence of atopy in patients with CD30CLPD in retrospective studies depends on patients’ recall which is not always reliable. More objective criteria of atopy include evidence of skin reactivity to allergens (positive prick test) and evidence of allergen-specific IgE in serum. This study was undertaken to test the hypothesis that atopy is prevalent in patients with CD30CLPD using serologic criteria of allergen-specific IgE antibodies to aeroallergens and Staphylococcal aureus enterotoxin superantigens (SSAgs).

Methods

We tested serum samples of CD30CLPD for common IgE-specific airborne allergens with the Phadiatop test, which if positive, is regarded as serologic evidence of atopy in adults. Sera were also tested for IgE antibodies reactive to three Staphylococcal enterotoxins with superantigenic properties (SSAg-IgE). Control sera were obtained from adult subjects evaluated for rhino-sinusitis and a negative Phadiatop test. Patients’ history of an atopic disorder was obtained by retrospective chart review.

Findings

Nearly 50% of patients with the most common LyP types (A and C) had a positive Phadiatop test for allergic sensitization to common airborne allergens, and total serum IgE (IgE-t) was increased compared to non-atopic controls. At the IgE antibody concentration generally used to define serologic atopy (≥ 0.35 kU_A/L), 8/31 (26%) samples of CD30CLPD and 7/28 (25%) samples of LyP were reactive to at least one SSAg-IgE compared to 3/52 (6%) control specimens (P = 0.016 and P = 0.028, respectively). TSST1-IgE was detected in 7 (23%) specimens of CD30CLPD, often together with SEB-IgE; SEA-IgE ≥ 0.35 kU_A/L was not detected. For control specimens, TSST1-IgE exceeded the 0.35 kU_A/L threshold in 3 (6%) specimens.

Conclusions

Patients with LyP types A and C have serologic evidence of atopy against common airborne antigens and SSAgs when compared to control adult subjects who had rhino-sinusitis and a negative Phadiatop test for aero-IgEs. Serologic evidence of atopy exceeded that determined by LyP patients’ personal history. The findings support our hypothesis that an atopic diathesis may contribute to the pathogenesis of the most common types of LyP (A and C).

Psoriasis and Microbiota: A Systematic Review

Background: Recent advances have highlighted the crucial role of microbiota in the pathophysiology of chronic inflammatory diseases as well as its impact on the efficacy of therapeutic agents. Psoriasis is a chronic, multifactorial inflammatory skin disorder, which has a microbiota distinct from healthy, unaffected skin. Aim: Through an extensive review of the literature, we aim to discuss the skin and gut microbiota and redefine their role in the pathogenesis of psoriasis. Conclusions: Unfortunately, the direct link between the skin microbiota and the pathogenesis of psoriasis remains to be clearly established. Apart from improving the course of psoriasis, selective modulation of the microbiota may increase the efficacy of medical treatments as well as attenuate their side effects.

Therapeutic targeting of Toll-like receptors: a review of Toll-like receptors and their signaling pathways in psoriasis

INTRODUCTION

Expression of various Toll-like receptors (TLR) in keratinocytes (KCs) has offered new insights into the pathogenesis of psoriasis. When plasmacytoid dendritic cells (pDCs) are scarce in established psoriatic lesions, KCs take the responsibility to secrete IFN type 1 through TLR9 activation. Antagonists of TLR7 and TLR8 and anti-IL-12/IL-23 substances have shown promising results in treating psoriasis. Areas covered: References in this study were extracted from Scopus, PubMed and Embase databases by the search term: ('Toll-Like Receptors' OR 'TLR') AND ('Psoriasis' OR 'Arthritis, Psoriatic' OR 'PsA'). Expert commentary: As the prevailing cell type, KCs play a major role in the maintenance of psoriatic lesions. By specific upregulation of IL-36 R, KCs can start the IL-23/IL-12 axis, leading to production of major culprits of psoriatic phenotype IL-17 and IL-22. Targeting IL-36 R could be considered as a new therapeutic target to eliminate cutaneous manifestations of psoriasis.

Effect of tonsillectomy on psoriasis: a systematic review

BACKGROUND

Streptococcal infection is associated with psoriasis onset in some patients. Whether tonsillectomy decreases psoriasis symptoms requires a systematic review of the literature.

OBJECTIVE

We sought to determine whether tonsillectomy reduces psoriasis severity through a comprehensive search of over 50 years of literature.

METHODS

We searched MEDLINE, CINAHL, Cochrane, EMBASE, Web of Science, and OVID databases (from August 1, 1960, to September 12, 2013) and performed a manual search of selected references. We identified observational studies and clinical trials examining psoriasis after tonsillectomy.

RESULTS

We included data from 20 articles from the last 53 years with 545 patients with psoriasis who were evaluated for or underwent tonsillectomy. Of 410 reported cases of patients with psoriasis who underwent tonsillectomy, 290 experienced improvement in their psoriasis. Although some patients who underwent tonsillectomy experienced sustained improvement in psoriasis, others experienced psoriasis relapse after the procedure.

LIMITATIONS

Fifteen of 20 publications were case reports or series that lacked control groups. Publication bias favoring reporting improved cases needs to be considered.

CONCLUSION

Tonsillectomy may be a potential option for patients with recalcitrant psoriasis associated with episodes of tonsillitis. Studies with long-term follow-up are warranted to determine more clearly the extent and persistence of benefit of tonsillectomy in psoriasis.

The rise of staphylococcal super antigens in psoriatic patients: a case-control study

BACKGROUND

Staphylococcus aureus, the major virulence factor of hospital and community acquired infections, secretes numerous exotoxins (super antigens), which may affect immunological and inflammatory status in psoriatic skin lesion.

OBJECTIVES

This study is designed to compare the S. aureus super antigens level in sera of psoriatic patients with normal cases (nevus).

PATIENTS AND METHODS

A case control study was performed in dermatology ward of Rasoul Hospital in Tehran, IR Iran (2008 - 2010). Staphylococcal super antigens (Entrotoxin A, B, D and TSST1) were measured in serum of 41 psoriatic patients and 28 normal persons (Nevus) by ELISA. Chi square values (CI 95%, P value < 0.05) were calculated for all categorical variables.

RESULTS

In this study 63.4% (26) of cases were male, 36.6% (15) were female. Age ranged from 4 months to 64 years old, with a mean age of 33.7 ± 15.4 years. Type of skin disease in cases: 20% (8) were inflicted by the Gutate form of the disease; 59% (23) with chronic plaque psoriasis (CPP), 7.7% (3) with erythrodermic and 12.8% (5) had other types of the disease (plaque, pustular, inverse). TSST (toxic shock syndrome toxin) was detected in 47% (20/41) of cases and in 6% (1/28) of the controls with a significant difference. (P value = 0.000) Entrotoxins (A, B, D) were detected in the sera of 48.8% (21/41) of cases; and only 6 %( 1/21) of controls, showed significant differences (P value = 0.000) positive TSST was more common in spring, and correlates with CPP type of psoriasis, but not related to patient`s gender and age.

CONCLUSIONS

In this study, S. aureus were 25 times more in psoriatic patients. Super antigens should be first detected in the serum samples; if negative, the skin lesions should be examined by PCR especially in chronic types of disease. Adding the antibiotics against S. aureus to other conventional treatments might be helpful. It has a more important and significant role in children with acuteinfection.

Streptococcal superantigens: categorization and clinical associations

Superantigens are key virulence factors in the immunopathogenesis of invasive disease caused by group A streptococcus. These protein exotoxins have also been associated with severe group C and group G streptococcal infections. A number of novel streptococcal superantigens have recently been described with some resulting confusion in their classification. In addition to clarifying the nomenclature of streptococcal superantigens and proposing guidelines for their categorization, this review summarizes the evidence supporting their involvement in various clinical diseases including acute rheumatic fever.

Keratin 17: a critical player in the pathogenesis of psoriasis

Keratin 17 (K17) is an intermediate filament protein present in the basal cells of complex epithelia, such as nails, hair follicles, sebaceous glands, and eccrine sweat glands. Studies have shown that it is expressed aberrantly in the suprabasal keratinocytes of psoriatic lesions, compared to in normal epidermis. K17 is also closely associated with the immune system and plays an important role in the pathogenesis of psoriasis. In this review, we present our experimental findings concerning the role of K17 in psoriasis, and compare them to results published in the literature. Our results show that cytokines related to Th17 and IL-22-producing (where Th17 is T helper cells, type 17 and IL is interleukin) CD4(+) T cells, including IL-17A and IL-22, upregulate the expression of K17 in keratinocytes. In addition, K17 stimulates autoreactive T cells and promotes the production of psoriasis-associated cytokines. Our findings lend support to the hypothesis that a K17/T-cell/cytokine autoimmune loop is involved in the pathogenesis of psoriasis. We therefore review the current understanding of the K17 immunoregulation, including its expression and direct/indirect effects on immune responses. Pertinent strategies for the treatment of psoriasis are also discussed.

Psoriasis epidemiology: the interplay of genes and the environment

Psoriasis is a common chronic dermatological disease whose prevalence varies among different populations worldwide. In epidemiological studies, the factors that potentially account for this variability include climate, genetic susceptibility, and environmental antigen exposure. In this issue, Parisi et al. performed a systematic review to explore the global prevalence and incidence of psoriasis.

HLA allele associations and V-beta T-lymphocyte expansions in patients with psoriasis, harboring toxin-producing Staphylococcus aureus

HLA alleles have been associated with psoriasis. Toxin-producing strains of Staphylococcus aureus behave as superantigens, and if present in patients, might play a role in the exacerbation of psoriatic lesions by activating certain V-beta (V beta) T-lymphocyte subsets. Allele frequencies in 22 patients and 22 controls (alleles determined by DNA/SSP typing) were used to calculate a relative risk of $4.7$ ($P < .05$) for HLA-Cw6. S aureus was isolated from the throat of 11 patients. Enterotoxins A and C were detected by agglutination in the culture filtrate of one isolate. The enterotoxin A and/or C genes were detected by PCR in 9 isolates, and transcripts were detected by RT-PCR in 7 of them. None of the isolates from controls harbored enterotoxin genes. V beta expansions were detected by RT-PCR in all 22 patients. Low or no V beta expansions were obtained in controls. The association of HLA-Cw6 with psoriasis in Lebanese concurs with that reported for other ethnic groups. Toxin-producing isolates that colonize patients might play a role in the exacerbation of psoriatic lesions.

Psoriasis and streptococci: the natural selection of psoriasis revisited

We have previously postulated that surviving invasive streptococcal infections may have been a factor in psoriasis becoming a common skin disease in some parts of the world. Many of the candidate genes linked to psoriasis are associated with the acquired or innate immune system, which are also important in host defence to invasive streptococcal infections. High rates of positive streptococcal throat swabs among patients with chronic plaque psoriasis suggest that they are efficient at internalizing/carrying beta-haemolytic streptococci. Internalization of streptococci in the throat is dependent upon the transforming growth factor (TGF)-beta/fibronectin/alpha 5 beta 1 integrin pathway. The immune cell Th17 and its related cytokine network are important in mucosal defence, being very effective against extracellular microbes but having little effect on intracellular organisms. The TGF-beta/fibronectin/alpha 5 beta 1 integrin pathway and the Th17 cell network also appear to be operative in psoriasis, animal models of both TGF-beta and alpha 5 beta 1 cutaneous overexpression being associated with characteristic psoriasis lesions. We postulate that some of the genotypic/phenotypic changes in different immunological pathways in psoriasis, including the acquired T-cell response, the innate immune response, the TGF-beta/fibronectin/alpha 5 beta 1 integrin pathway and the Th17 cell system, confer protection against mortality during epidemics of invasive streptococcal infections, heightened efficiency in internalizing and allowing carriage of streptococci as well as predisposition to the development of psoriasis.

A new therapeutic approach to treat psoriasis by inhibition of fatty acid oxidation by Etomoxir

BACKGROUND

The dogma in psoriasis is that due to pathogen-induced inflammatory responses, an autoreactive immune response is induced that leads to tissue destruction. However, this model might be too simplistic. Literature data suggest that the expression of enzymes crucial for fatty acid oxidation is upregulated in the skin of patients with psoriasis compared with healthy individuals.

OBJECTIVES

To examine the influence of fatty acid oxidation on psoriasis with regard to expression and activity of the key enzyme in fatty acid oxidation, carnitine palmitoyltransferase-1 (CPT-1) and the effect of the CPT-1 inhibitor, Etomoxir.

METHODS

Experiments were performed with homogenates of lesional and healthy skin, fibroblast cultures and a model of human psoriatic skin transplanted on immune-deficient BNX mice.

RESULTS

CPT-1 was highly active in lesional skin. Etomoxir was able to block CPT-1 activity in skin, implying that this antagonist may have the potential to suppress psoriasis when administered topically. In the mouse model, Etomoxir had an antipsoriatic effect that was at least as good as that of betamethasone, as evidenced by reduction of epidermal thickness, keratinocyte proliferation and differentiation.

CONCLUSIONS

We conclude that fatty acid metabolism and in particular CPT-1 may be an excellent target for treatment of psoriasis.

Expression of cutaneous lymphocyte-associated antigen (CLA) in tonsillar T-cells and its induction by in vitro stimulation with alpha-streptococci in patients with pustulosis palmaris et plantaris (PPP)

Pustulosis palmaris et plantaris (PPP) is known to be a one of the tonsil-related diseases because tonsillectomy is quite effective in curing this condition. However etiological association between tonsils and PPP have not fully clarified yet. Cutaneous lymphocyte-associated antigen (CLA) is known to be a specific homing receptor that facilitates T-cell migration into skin. In this study, we investigated the expression of CLA on T-cells in tonsil, peripheral blood, and skin from patients with PPP. Two-color flow cytometric and two-color immunohistological analyses revealed that the numbers of CLA/CD3 double-positive cells in freshly isolated tonsillar mononuclear cells (TMC) and in tonsillar tissues were significantly higher in patients with PPP than in patients without PPP (P<0.01, each). In vitro stimulus with alpha-streptococcal antigens enhanced CLA expression of tonsillar T-cells and TGF-beta production of TMC in patients with PPP (P<0.01, each), but did not in patients without PPP. In peripheral blood from PPP patients, the number of the CLA/CD3 double-positive cells significantly decreased at 6 months after tonsillectomy (P<0.05). The CLA/CD3 double-positive cells and the postcapillary venule that expressed with a ligand of CLA, E-selectin, were found more frequently in the plantar skin from patients with PPP as compared to that from healthy volunteers (P<0.01, each). These data suggest that a novel immune response to alpha-streptococci may enhance CLA expression on tonsillar T-cells through TGF-beta production in patients with PPP, resulting in moving of CLA-positive tonsillar T-cells to skin and tissue damages. This may play a key role in pathogenesis of PPP.

Therapeutic potential of macrolide immunosuppressants in dermatology

Dermatologists are frequently presented with inflammatory dermatoses that are responsive to treatment with immunomodulating drugs. Corticosteroids, particularly when applied topically, have been the mainstay of treatment in the past. Their undoubted efficacy, however, has been undermined by problems with repeated use including tachyphylaxis and side effects such as skin atrophy and hypertension. Macrolide immunosuppressive drugs, originally used for prophylaxis of organ transplant rejection, have been shown to be effective in the treatment of inflammatory dermatoses. The original drugs used in dermatology in this class have their own limitations including poor absorption when used topically and their distinct side-effect profiles. A search for other immunosuppressive macrolide antibiotics has led to the development of new agents, which have enhanced profiles for the treatment of skin disease. This review discusses the main dermatoses that may be targeted by this class of drugs and summarises the topical and systemic macrolides either currently in use, in clinical trials or preclinical development.

Interferon-gamma-dependent in vitro model for the putative keratin 17 autoimmune loop in psoriasis: exploration of pharmaco- and gene-therapeutic effects

In 1999, A.S. Gudmundsdottir et al. have envisaged an epitope on keratin 17 (K17) as a putative psoriasis major autoantigen recognized by T cells. In a HaCaT keratinocyte model, we now demonstrate that IFN-gamma and to a less extent also TNF-alpha and TGF-alpha are able to induce K17 protein expression, in contrast to IL-1alpha, IL-1beta, IL-6, IL-8 and IL-18. This supports our hypothesis of an existing proinflammatory cytokine/K17 autoimmune loop as a presumptive positive feedback mechanism driving psoriasis etiopathogenesis. K17 overexpression was now found to also coincide with suppression of keratinocyte proliferation, e.g. induced by NF-kappa B inhibitors (Bay 11-7082 and Bay 11-7085), and thereby correlated hyperapoptosis to be encountered in psoriatic epidermis. Acitretin as an established antipsoriatic drug and the tyrosine kinase inhibitor imatinib decreased, whereas hydrocortisone as well as dexamethasone increased the IFN-gamma-induced K17 overexpression. The latter might be another mechanism explaining the well-known rebound phenomena after abrupt withdrawal of corticosteroids in psoriasis treatment. Finally, we defined a K17-directed and effective antisense oligodesoxynucleotide which may hold promise for future gene-therapeutic approaches in psoriasis.

Methotrexate markedly reduces the expression of vascular E-selectin, cutaneous lymphocyte-associated antigen and the numbers of mononuclear leucocytes in psoriatic skin

A positive correlation between disease severity and the frequency of cutaneous lymphocyte-associated antigen (CLA)-positive T cells in the blood of untreated patients with psoriasis has been previously observed. A dose-dependent inverse relationship between disease severity and the frequency of circulating CLA(+) T cells in psoriasis patients on methotrexate (MTX) treatment is reported. Circulating T cells from a patient with psoriasis were monitored for CLA expression on a daily basis for 5 weeks. A decrease in the intensity and frequency of CLA(+) mononuclear leucocytes was consistently observed in the blood during the first 3-4 days after each MTX intake, but the CLA expression increased thereafter until the next weekly dose was taken. The MTX treatment of this patient was then discontinued for 16 days, and a marked subjective exacerbation was reported within 9 days, which was confirmed objectively (laser Doppler perfusion imaging) after 11 and 16 days. Biopsies taken 4 days after the last MTX intake showed only a few mononuclear leucocytes in lesional skin, but the exacerbation coincided with a marked increase in CLA expression by mononuclear blood leucocytes, followed by an increase in endothelial E-selectin and a striking influx of CLA(+) mononuclear cells into lesional skin. Conversely, a clinical improvement after the patient resumed the MTX treatment was associated with reduction in CLA expression by mononuclear cells in the blood, downregulation of endothelial E-selectin and an approximate threefold decrease in mononuclear leucocyte infiltration of lesional skin. No MTX-associated changes were detected in the expression of very late antigen-4, vascular cell-adhesion molecule-1 nor the late activation marker CD25. It is concluded that MTX decreases the expression of CLA and E-selectin and that this may be a major mechanism for the therapeutic effect of MTX on psoriatic skin lesions.

HLA class II polymorphisms determine responses to bacterial superantigens

The excessive immunological response triggered by microbial superantigens has been implicated in the etiology of a wide range of human diseases but has been most clearly defined for the staphylococcal and streptococcal toxic shock syndromes. Because MHC class II presentation of superantigens to T cells is not MHC-restricted, the possibility that HLA polymorphisms could influence superantigenicity, and thus clinical susceptibility to the toxicity of individual superantigens, has received little attention. In this study, we demonstrate that binding of streptococcal and staphylococcal superantigens to HLA class II is influenced by allelic differences in class II. For the superantigen streptococcal pyrogenic exotoxin A, class II binding is dependent on DQ alpha-chain polymorphisms such that HLA-DQA1*01 alpha-chains show greater binding than DQA1*03/05 alpha-chains. The functional implications of differential binding on T cell activation were investigated in various experimental systems using human T cells and murine Vbeta8.2 transgenic cells as responders. These studies showed quantitative and qualitative differences resulting from differential HLA-DQ binding. We observed changes in T cell proliferation and cytokine production, and in the Vbeta specific changes in T cell repertoire that have hitherto been regarded as a defining feature of an individual superantigen. Our observations reveal a mechanism for the different outcomes seen following infection by toxigenic bacteria.

Rapid analysis of the Vβ repertoire of CD4 and CD8 T lymphocytes in whole blood

Determination of the T cell receptor Vbeta repertoire of human CD4 and CD8 populations is a useful immunological tool, particularly in the investigation of superantigen involvement in various disease states. We describe the optimisation of a rapid technique for the simultaneous evaluation of 24 Vbeta families of the T cell receptor of CD4 and CD8 positive lymphocytes in whole blood by flow cytometry adapting a commercially available monoclonal antibody kit. The technique described is reliable and reproducible, and we describe its use as a potential diagnostic tool in patients with staphylococcal and streptococcal toxic shock syndromes.

Interleukin-12 alone can not enhance the expression of the cutaneous lymphocyte associated antigen (CLA) by superantigen-stimulated T lymphocytes

It has been reported that bacterial superantigens induce interleukin (IL)-12 dependent expression of the cutaneous lymphocyte associated antigen (CLA) and that this may be relevant to the association between certain skin diseases and infections including psoriasis and streptococcal tonsillitis. We have confirmed that the streptococcal pyrogenic superantigen C (SpeC) increases CLA expression by both CD4+ and CD8+ T cells when PBMCs are incubated in medium enriched with fetal calf serum (FCS). However, such an increase could not be induced in medium enriched with human serum (HS) even when recombinant IL-12 was added to the PBMCs cultures. Strikingly, CD4+ T cells incubated with SpeC in HS showed a marked reduction in CLA expression, which was not due to apoptosis. In contrast, SpeC did induce T cell proliferation and expression of CD25, CD54 and CD103 in the presence of HS indicating that the absence of SpeC induced CLA expression in HS was not due to SpeC inhibitors. Although addition of low amounts of lipopolysaccharide endotoxin (LPS) caused a highly significant increase in CLA expression in the absence of SpeC in cultures enriched with HS, a combination of LPS and SpeC did not increase CLA expression beyond that induced by LPS alone. The superantigen-induced CLA expression in FCS was partially inhibited by anti-IL-12 but not by anti-IL-18 or antibodies to transforming growth factor (TGF)-beta. It is concluded that IL-12 alone can not increase CLA expression but requires the help of other factor(s) present in FCS but not in HS. Although LPS can induce CLA expression it does not seem to be the factor that interacts with IL-12 to induce superantigen-mediated CLA expression in cultures enriched with FCS.