Psoriasis and leukocyte chemotaxis

Pathophysiology of generalized pustular psoriasis

Generalized pustular psoriasis (GPP) is a serious dermatological disease characterized by fever, chills, rigors, and generalized pustule formation on the skin. Previous analyses in Japan have led to the proposal to divide GPP into two groups, one with a history of ordinary psoriasis (pso(+) GPP) and the other without a history of psoriasis (pso(-) GPP). Clinically the onset of the pustular outbreak is earlier in pso(-) GPP, which occurs more frequently after infections, whereas pso(+) GPP occurs more frequently following corticosteroid therapy. Substantial differences are also noted in HLA analyses. Activation of neutrophils is a basic mechanism in both types of GPP. Although the epidermal structural changes in GPP are usually not so prominent as those in psoriasis vulgaris, pso(+) GPP shows a more psoriasiform architecture than pso(-) GPP. Analysis of epidermal cell proliferation in GPP indicates that it is not less than that seen in psoriasis vulgaris. The occasional psoriasiform epidermal architecture especially seen in pso(+) GPP may be considered to be a steady-state condition achieved after epidermal cell proliferation has continued for a sustained period. Various inflammatory cytokines appear to be involved in the neutrophilic infiltrate seen in GPP.

Normal proliferative responses of peripheral blood mononuclear cells to streptococcal preparation OK-432 in patients with pustulosis palmaris et plantaris constitute a distinct feature from the reduced responses observed in those with psoriasis vulgaris, pustular psoriasis, and acrodermatitis continua of Hallopeau

It was previously reported that peripheral blood mononuclear cells (PBMC) from the patients with psoriasis vulgaris (PV) showed a reduced proliferative response in vitro to the stimulation of a lyophilized preparation of penicillin-treated low virulence Su-strain of Streptococcus pyogenes group 3, OK-432. In this study, at first it was examined whether OK-432 acts as a superantigen. By analyzing the usage of Vbeta T-cell receptor (TCR) of proliferating T cells stimulated with OK-432, it was found that OK-432 stimulated preferentially Vbeta2 TCR-bearing T cells. Next, to find differences in in vitro responses of PBMC among various types of sterile pustular dermatoses such as pustulosis palmaris et plantaris (PPP), acrodermatitis continua of Hallopeau (AC), and generalized pustular psoriasis (GPP), the proliferative responses of PBMC obtained from these patients under the stimulation of OK-432 were compared. When the PBMC was stimulated with interleukin (IL)-2, no significant difference was found in their proliferative responses among those obtained from the patients with these sterile pustular dermatoses, PV or healthy controls. However, like those from PV patients, PBMC from AC and GPP patients showed significantly smaller responses to OK-432 than those from the healthy controls. In contrast, the proliferative responses of PBMC from the patients with PPP to OK-432 was comparable to those from healthy controls. These results, in addition to its unique clinical and histopathological characteristics, suggest that PPP has a different pathogenetic background from that underlying PV, AC, or GPP.

Inflammatory and immune reactions associated with stratum corneum and neutrophils in sterile pustular dermatoses

In this review we present our own experimental findings as well as those from the literature related to the pathomechanisms for the inflammatory changes in psoriasis and its related diseases. A growing body of evidence has indicated that T cell-mediated immunity plays an important role in triggering and maintenance of psoriatic lesions. It has been revealed that lymphokines produced by activated T cells in psoriatic lesions have a strong influence on the proliferation of the epidermis. Characteristic neutrophil accumulation under the stratum corneum can be observed in the highly inflamed areas of psoriatic lesions. These neutrophils are chemotactically attracted and activated there by synergistic action of chemokines, IL-8 and Gro-alpha released by stimulated keratinocytes, and particularly by C5a/C5a des arg produced via the alternative complement pathway activation. We demonstrated that the infiltrating neutrophils adhere to iC3b-opsonized corneocytes to produce active oxygen and probably lysosomal enzymes. From a close relationship observed between neutrophil accumulation and high mitotic ratio of the lesional epidermis, we think that these stimulated neutrophils influence the growth and differentiation of epidermal keratinocytes. Aberrant expression of HLA-DR on neutrophils suggests their activation of infiltrating T cells in the presence of bacterial superantigen. These T cells in turn influence the transepidermal neutrophil migration through the effect of their cytokines on the keratinocyte production of proinflammatory mediators including IL-8 and C3. In this review we discuss the pivotal roles played by stratum corneum and neutrophils in several skin diseases, where neutrophils accumulate beneath the stratum corneum in a sterile condition.

Psoriasis is a visible manifestation of the skin's defense against micro-organisms

The recent discovery that human epidermal cells themselves make and secrete the components necessary for activation of the alternative complement pathway appears to provide an explanation for how human skin is ordinarily able to avoid colonization by molds and other organisms. It also helps clarify the mechanisms underlying clinical and laboratory findings seen in chronic mucocutaneous candidiasis, dandruff, and psoriasis. Psoriasis seems best explainable as a visible, late stage of the inflammatory sequelae of activation of the alternative complement pathway in the epidermis.

A distinct stratum corneum antigen in psoriasis and its reactions with stratum corneum autoantibodies

Stratum corneum antibodies are ubiquitous and can be detected by various immunological methods. Of these, the ones detected by hemagglutination undergo changes in antibody titers and have been implicated in psoriasis. The purpose of our study was to examine if differences exist in the activities of the antigens isolated from psoriatic scales in comparison to normal callus. Stratum corneum antigens were prepared by trypsin-phenol-water extraction. The water phase, which contains the stratum corneum antigen, was used to sensitize the red blood cells in the hemagglutination assay. The antibody activity in human sera was determined before and after absorption with antigens isolated from callus, psoriatic scales, and cell envelopes. We found notable differences in the antigens obtained from callus and psoriatic scales. These include higher antibody titers to the antigens of the scales, the presence of unique antigenic determinants on psoriatic scales and the localization of the antigen on cell envelopes. These immunological differences were corroborated by the marked biochemical differences of certain amino acids, most notably glycine and proline, and these differences were unique to psoriatic scales as they were not shared with other hyperproliferative disorders.

Autologous mixed lymphocyte reaction is reduced in patients with psoriasis

The autologous mixed lymphocyte reaction (auto-MLR) was studied to test the interactions between immunocompetent cells in patients with psoriasis. The auto-MLR in 20 patients with psoriasis was significantly lower than in 16 normal controls. Lower values were found in untreated psoriatic patients than in those in remission following treatment. The values in the latter group were significantly lower than in controls and in six patients with atopic dermatitis in remission. The tendency for an increase in the auto-MLR with a decrease in disease activity was further confirmed in five patients studied before and after treatment. In contrast, the allogeneic lymphocyte reaction (allo-MLR) in psoriatics was similar to that in normal controls.

The psoriasis-associated antigen, pso p27, participates in the formation of complement activating immune-complexes in psoriatic scale

The psoriasis-associated antigen, pso p27, and antibodies recognizing this antigen were demonstrated in extracts from psoriatic scales. It was demonstrated that the antigen was present in complexes containing IgG as well as complement factor C1q. The complexes were studied with respect to complement-activating potential. This was measured as the ability of the complexes to induce the generation of the complement factor C5a using rabbit serum as the source of complement. The data obtained showed that the pso p27-containing complexes were able to activate the complement system, indicating that the pso p27 antigen may contribute to the inflammatory process in psoriasis.

The eosinophil granulocyte in psoriasis

The presence of eosinophils and eosinophil cationic protein (ECP) in the involved and non-involved skin in patients with psoriasis was studied using a polyclonal antibody specific for ECP and a monoclonal antibody (EG2) specific for activated eosinophils and secreted ECP. ECP immunoreactive eosinophils were found in all the specimens from involved psoriatic skin. In new lesions in patients with rapidly progressive disease, intense ECP immunoreactivity was detected both intra- and extracellularly, particularly in the upper third of the epidermis and usually in association with granulocytes. In stable or slowly progressive lesions, less ECP was observed. The EG2-immunoreactivity was positive in the same areas. ECP was also determined in suction-blister fluid from lesional and non-involved skin in psoriasis patients and in healthy subjects. The ECP concentration was greatly elevated in the fluid from lesions in patients with more acute and progressive disease.

Complement activation in psoriasis

Plasma from 16 patients with psoriasis and 12 healthy control subjects were measured for iC3b, C4d, and Bb fragments generated by complement activation. Plasma concentrations for iC3b, C4d, and Bb fragments were found to be significantly increased in the patients with psoriasis. The highest concentrations of these complement activation fragments were seen in patients with erythrodermic pustular psoriasis, psoriatic arthritis, and Reiter's syndrome. The serum concentrations of complement components and regulatory proteins were normal or elevated in almost all samples.

Demonstration of neutrophil chemotactic anaphylatoxins in human dandruff

In contrast to scales collected from the scalps of nine healthy individuals where a few parakeratotic cells are observable, a large number of parakeratotic cells associated with some infiltrated polymorphonuclear leukocytes (PMNLs) were found in the scales obtained from 11 individuals complaining of dandruff. Therefore, we determined the neutrophil chemotactic properties of the water-soluble extracts of dandruff scales and normal control scalp scales. Aqeous extracts fractionated by Sephadex G-75 showed a potent chemotactic activity only in the fractions of the dandruff patients that eluted with cytochrome C marker (cyt C; molecular weight, 12 kDa). It was comparatively stable to heat but was greatly inhibited by the addition of anti-C5 antiserum. Radioimmunoassay demonstrated that, although small amounts of C5a and C4a anaphylatoxins were demonstratable even in the extracts of normal scalp, they were found in significantly increased amounts in the extracts of dandruff. Moreover, there was a significantly positive correlation between C5a and C4a concentrations in these extracts. These results suggest that classical complement pathway activation with resultant production of C5a anaphylatoxin is involved in the migration of PMNLs into the lesional skin of dandruff.