Richard D.R. Camp

More than skin deep: atherosclerosis as a systemic manifestation of psoriasis.

There is now growing evidence that psoriasis, like other inflammatory diseases such as rheumatoid arthritis and systemic lupus erythematosus, is a systemic disorder that is associated with enhanced atherosclerosis and risk of coronary artery disease. Here we summarize the available epidemiological evidence for this association and analyse pathogenic features that are common to psoriasis and atherosclerosis. Further prospective studies are urgently needed to extend knowledge of the risk of cardiovascular morbidity and mortality in patients with psoriasis and to confirm the degree to which treatment of psoriasis reduces this risk. Nevertheless, existing data are sufficient to indicate that severe psoriasis should be more widely recognized as a potential risk factor for cardiovascular disease and should be considered with the established factors when formulating strategies for the management of cardiovascular risk.

Potent Costimulation of Effector T Lymphocytes by Human Collagen Type I

Purified, resting peripheral blood T lymphocytes were previously reported to undergo β1 integrin-dependent activation when cultured with anti-CD3 mAb coimmobilized with fibronectin, but not type I collagen. However, the extravascular T cells that encounter immobilized extracellular matrix proteins and are involved in disease pathogenesis have different properties from resting peripheral blood cells. In this study, we confirm that resting CD4+ and CD8+ T cells from peripheral blood are costimulated by immobilized fibronectin, but not type I collagen. In contrast, Ag- or mitogen-stimulated CD4+ and CD8+ T cell lines, used as models of the effector cells involved in disease, are more potently costimulated by type I collagen than fibronectin. The collagen-induced effects are similar in assays with serum-free medium and in more physiological assays in which anti-CD3 mAb is replaced by a threshold concentration of Ag and irradiated autologous PBMC as APC. The responses are β1 integrin dependent and mediated largely by very late Ag (VLA) 1 and 2, as shown by their up-regulation on the T cell lines as compared with freshly purified resting PBL, and by the effects of blocking mAb. Reversed phase HPLC located the major costimulatory sequence(s) in the α1 chain of type I collagen, the structure of which was confirmed by amino acid sequencing. The results demonstrate the potential importance of type I collagen, an abundant extracellular matrix protein, in enhancing the activation of extravascular effector T cells in inflammatory disease, and point to a new immunotherapeutic target.

Induction of in vitro human lymphocyte migration by interleukin 3, interleukin 4, and interleukin 6.

The effects of interleukin 3 (IL 3), IL 4, IL 6, and interferon-gamma (IFN-gamma) on lymphocyte migration have been investigated and compared with those of transforming growth factor-beta 1 (TGF-beta 1), granulocyte colony stimulating factor (GCSF), and macrophage colony stimulating factor (MCSF). Potent, temperature-dependent stimulation of lymphocyte migration was obtained in response to IL 3 and IL 4 (ED50 less than 10(-11) M and less than 10(-13) M, respectively) and this migration was abolished in the presence of 3 micrograms ml-1 cytochalasin B. IL 6 and IFN-gamma were less active (ED50 greater than or equal to 10(-9) M and greater than or equal to 10(-8) M, respectively), maximal migration in response to IFN-gamma being only 30% above background as compared with approximately 250% for IL 3 and IL 4. TGF-beta 1, GCSF, and MCSF failed to stimulate lymphocyte migration in doses similar to those used for IL 3, IL 4, and IL 6. The presence of antisera to IL 3, IL 4, and IL 6 specifically inhibited lymphocyte migration induced by the corresponding cytokines (IC50 values being 1/10,000, greater than 1/30,000, and greater than 1/30,000 dilution of antibody, respectively). Cross-desensitization experiments using IL 3 and IL 4 demonstrated that neither IL 3 nor IL 4 were able to stimulate dose-related lymphocyte migration in cells preincubated with IL 3. Cells preincubated with IL 4 were only stimulated by a supraoptimal concentration of IL 4 (10(-11) M). The induction of lymphocyte migration by IL 3, IL 4, and IL 6 therefore appears to be a specific and potentially important effect of these cytokines. Cross-desensitization of lymphocytes by IL 3 and IL 4 raises the possibility that the induction of lymphocyte migration by these cytokines may occur through a common postreceptor signal transduction mechanism.

Humoral Autoimmune Responses to the Squamous Cell Carcinoma Antigen Protein Family in Psoriasis

Substantial evidence indicates that psoriasis is a T-lymphocyte-mediated autoimmune disease. However, longstanding data also indicate IgG and complement deposition in upper epidermis of psoriasis plaques. This led us to propose that autoantigen-autoantibody interactions in the skin may also be of pathogenic importance. Here, we have confirmed the presence of IgG in upper lesional epidermis and used high-resolution two-dimensional immunoblotting of extracts from this tissue, and laser desorption mass spectrometry of tryptic peptides, to define a series of epidermal proteins that bind IgG from psoriatic serum. The most prominent of these autoantigens are homologues of the serpin, squamous cell carcinoma antigen (SCCA), the other autoantigens identified including arginase 1, enolase 1, and keratin 10. Blood levels of IgG autoantibodies that bind to SCCA proteins were significantly higher in psoriasis than healthy controls (P=0.005), but were not detectable in sera from patients with active atopic dermatitis. To our knowledge, SCCA proteins have not previously been described as autoantigenic in animals or humans and form complexes with IgG that are associated with complement deposition. These findings expose potentially pathogenic humoral immunologic events and thus possible therapeutic targets in psoriasis.

Antigen-independent expansion of T cells from psoriatic skin lesions : phenotypic characterization and antigen reactivity

The pathogenesis of psoriasis appears to depend on T cells, which have been proposed to mediate the disease through an autoimmune process. To test this hypothesis we have propagated four T‐cell lines from biopsies of psoriatic skin lesions by antigen‐independent methods. Flow cytometric immunophenotyping showed the lines to be composed mainly of CD4‐positive, αβ‐cell receptor (TCR)‐positive cells, which secreted a cytokine profile suggestive of predominant T‐helper type 1 (Th1) status. Analysis of TCR variable region (Vβ) usage revealed two‐ to eight‐fold increases in the expression of certain Vβ species in lesional lines as compared with autologous peripheral blood mononuclear cells (PBMC), with the increased Vβ species being expressed on more than 5% of cells in two of the lines. Lines were also used to test for responses to a range of epidermal antigen preparations in the presence of irradiated autologous PBMC as antigen‐presenting cells. The lines failed to proliferate in response to psoriatic lesional stratum corneum extracts, dispase‐separated normal human epidermal extracts, and an epidermal keratin preparation before and after trypsinization, in spite of good proliferative responses to anti‐CD3 which indicated that the lines were not anergic. In addition, the lines and PBMC from normal volunteers and the patients with psoriasis gave little or no response to recombinant streptococcal M protein. Thus, in spite of accumulating evidence for selective expansion of certain Vβ‐expressing T cells in psoriatic lesions, epidermal autoantigens have not been identified by using a bioassay which depended largely on the proliferation of lesional CD4‐positive cells. The role of streptococcal M protein, which bears some homology with epidermal keratin is also open to question, at least in chronic plaque psoriasis. Further work is therefore required to obtain direct evidence that autoimmune processes are important in the pathogenesis of chronic plaque psoriasis.

Potent and selective inhibition of in vitro lymphocyte migration by cyclosporine and dexamethasone.

We have studied the in vitro effects of cyclosporine A (CsA) and dexamethasone on lymphocyte migration, which is considered to play an important role in the pathogenesis of inflammatory and auto-immune disorders. Using a 48-well microchemotaxis assay, dose-related migratory responses of mixed peripheral blood lymphocytes (PBL) to recombinant interleukin (rIL)-1 alpha, rIL-2, leukotriene B4 (LTB4) and zymosan activated plasma (ZAP) were demonstrated. When preincubated with PBL under plasma free conditions and in the presence of undiluted autologous plasma, CsA in the dose range 4 x 10(-13)-1.6 x 10(-7) M caused concentration related inhibition of lymphocyte migration in response to fixed concentrations of rIL-1 alpha and rIL-2. CsA in the same dose range had no effect on the migration of PBL in response to ZAP and LTB4. Under plasma-free conditions dexamethasone (1 x 10(-11)-4 x 10(-6) M) caused concentration related inhibition of PBL migration in response to rIL-1 alpha and LTB4, but had no effect on the responses to rIL-2 and ZAP. These data provide evidence that CsA and dexamethasone are potent and selective inhibitors of in vitro lymphocyte migration, effects which may contribute to their therapeutic efficacy in vivo.

Characterisation of the in vitro responsiveness of lymphocyte subsets to locomotor stimuli by immunocytochemical methods.

The in vitro locomotion of lymphocyte subsets has previously been determined by use of highly purified cell populations. A method is now described in which mixed peripheral blood lymphocytes (PBL) migrate to the undersurface of polycarbonate filters in a 48 well microassay, the responding cells being characterised by alkaline phosphatase-anti-alkaline phosphatase immunocytochemistry. Recombinant interleukin (rIL)-1 alpha, zymosan activated plasma (ZAP) and rIL-8 were shown to induce concentration-related migration of mixed PBL in the 48 well assay and were therefore used as reference agonists. Total T cells, B cells, T helper/inducer and T suppressor/cytotoxic cells, as well as lymphocytes stained with the monoclonal antibodies UCHL1 and SN130, have now been quantified after migration to the undersurface of 8 microns pore size polycarbonate filters, in response to optimal concentrations of rIL-1 alpha, ZAP and rIL-8. The value of the analytical method was demonstrated by the selective responses seen. rIL-1 alpha selectively stimulated the migration of T helper/inducer and a small number of B cells without affecting T suppressor/cytotoxic cell locomotion. ZAP and rIL-8 significantly stimulated the migration of T helper/inducer, T suppressor/cytotoxic and B cells. ZAP and rIL-1 alpha also stimulated the migration of both UCHL1 and SN130 positively stained cells. This method may therefore be used to investigate the selective actions of lymphocyte locomotor stimuli on PBL sub-populations without the need to purify specific cell subsets, and to study the specificity of certain inhibitors or drugs on lymphocyte responses.

Novel cyclic and linear oligopeptides that bind to integrin β1 chain and either inhibit or costimulate T lymphocytes

There is a redundancy of cellular beta1 integrin (very late antigen or VLA) receptors that mediate interactions between different extracellular matrix proteins (ECMP) and T lymphocytes. This suggests that antagonists targeted at individual VLA receptors may be of limited therapeutic efficacy in T cell-mediated diseases and that agents such as monoclonal antibody 4B4, which bind to the common integrin beta1 chain and inhibit interactions between effector T cells and a range of ECMP, may be of greater therapeutic interest if toxicity can be avoided. We have therefore sought proof of principle as to whether small molecules that interact with the integrin beta1 chain at or near the 4B4 binding site can modulate T cell costimulation and adhesion in the presence of type I collagen or fibronectin (FN). Two phage display libraries, each expressing more than 10(9) independent cyclic or linear 7-mer peptides, were used to identify molecules of interest by an enrichment process involving specific recovery of phage bound to a human T cell line by elution with a large excess of 4B4 antibody. Novel cyclic and linear peptides have thus been identified and found to inhibit interactions between T cells and both type I collagen and fibronectin. A separate cyclic peptide was found to costimulate T cells in a beta1 integrin-dependent manner. These findings form a basis for the development of small molecules that interact in inhibitory or stimulatory capacities with the common integrin beta1 chain, and may be of interest as therapeutic antagonists or immunologic adjuvants.

Updates from the Third International Congress on Psoriasis: From Gene to Clinic, The Royal College of Physicians, London, U.K., 21–23 November 2002

The fourth ‘Psoriasis: From Gene to Clinic’ meeting was held in December 2005, its international status confirmed by the presence of almost 300 delegates from Europe, North America, Asia and Australasia. The meeting was co‐organized by Jonathan Barker (St Johns Institute of Dermatology, London) and Chris Griffiths (University of Manchester), who once again deserve congratulations for the success of their initiative. As its title suggests, the meeting was targeted at both clinical and basic scientists with a special interest in psoriasis, but in preparing this report the writer has selected presentations that caught his attention and that he felt able to review in a manner that might be of interest to the general readership of this Journal.

Arachidonate Lipoxygenase Products and Psoriasis

Psoriasis is a common skin disease that, in many cases, appears to be genetically determined. Lesional skin is characterized by epidermal proliferation and inflammatory changes, of which intraepidermal neutrophil infiltration is a consistent finding and one of the earliest abnormalities seen in developing lesions (Chowaniec et al., 1981). Psoriasis may manifest clinically in various forms, of which the chronic, stable, scaly plaque type is the most common. However, the inflammatory changes predominate in some patients, and in generalized pustular psoriasis, an uncommon form of the disease, intraepidermal neutrophil microabscesses are the major pathological feature (Baker and Wilkinson, 1979). These findings suggest that the production of neutrophil chemoattractants by the epidermis may be important in the pathogenesis of psoriasis.