Decreased natural killer cell activity in generalized pustular psoriasis (von Zumbusch type)

Natural killer cells from psoriasis vulgaris patients have reduced levels of cytotoxicity associated degranulation and cytokine production

Psoriasis vulgaris is a chronic inflammatory disease of the skin with a strong genetic component and immune system involvement. Although some evidence suggests that Natural Killer (NK) cells may play a part in psoriasis, their role is relatively unstudied and results are controversial. In this current study, NK cells from psoriasis patients exhibited reduced degranulation and produced lower levels of the pro-inflammatory cytokines IFN-γ and TNF-α. Further investigation found that NK cells from psoriasis patients and healthy controls expressed similar levels of activation markers, NK cell receptors and apoptosis-inducing molecules. In addition, comparable levels of several cytokines important in NK cell biology were found in the serum of psoriasis patients and healthy controls. Genotyping analysis revealed that HLA-C2, which provides a ligand for killer-cell immunoglobulin-like receptors (KIR) expressed by NK cells, was strongly associated with psoriasis susceptibility. However, no link between the KIR genes themselves and disease was found.

Mice lacking endogenous major histocompatibility complex class II develop arthritis resembling psoriatic arthritis at an advanced age

OBJECTIVE

To describe and characterize a novel inflammatory toe disease with severe bone destruction that developed spontaneously in "humanized" (HLA transgenic) mice lacking their own major histocompatibility complex (MHC).

METHODS

We studied 5 different HLA transgenic mouse lines (HLA-DR2.Ab(0), DR3.Ab(0), DR4.Ab(0), DQ6.Ab(0), and DQ8.Ab(0)) in similar genetic background for an extended period of time (>14 months). Clinical, radiologic, and histologic abnormalities were monitored, and the MHC-related major immunologic parameters in affected and resistant mice were compared.

RESULTS

Animals of 4 transgenic lines (HLA-DR2.Ab(0), DR4.Ab(0), DQ6.Ab(0), and DQ8.Ab(0)) developed severe toe inflammation accompanied by progressive bone resorption, hyperkeratosis, alopecia, loss of nails, and shortening and thickening of the distal phalanges. HLA-DR3.Ab(0) transgenic mice were resistant to inflammation. The disease manifested only at advanced ages (6 months or older) and affected 70-100% of the mice, with a female preponderance. The clinical signs and the radiographic and histopathologic features of the affected toes were not similar to those of any disease previously described in mice but did resemble those described for human psoriatic arthritis (PsA). Mice from the 4 susceptible lines expressed lower levels of the HLA transgene and exhibited significantly fewer CD4+ cells in the peripheral blood and reduced natural killer cell activity compared with mice from the resistant HLA-DR3.Ab(0) line.

CONCLUSION

This novel, spontaneously developing PsA-like toe disease in MHC-manipulated mice seems to be related to the absence of endogenous MHC class II. Replacement with HLA transgene expression that is insufficient (or no replacement at all) may result in imbalanced MHC class I and class II functions and lead to development of the disease.

Natural killer cell activity, serum immunoglobulins, complement proteins, and zinc levels in patients with psoriasis vulgaris

The role of the immune system in patients with psoriasis vulgaris (PV) was investigated. The genetic and immunological basis for psoriasis is still unknown. Because of the reports of immunological defects in this disease, we investigated serum levels of immunoglobulins IgG, IgM, IgA, complement proteins C3, C4, serum zinc (Zn) levels and natural killer (NK) cell activities. Skin lesions of the psoriatic patients involved in the study comprised less than 10 % of the total body and the disease was in a stationary period. Zn levels were measured by atomic absorption spectrophotometry. NK cell activity was measured by 51Cr (Na2 51CrO4). IgG, IgA, IgM, C3 and C4 assays were done by liquid-phase immunoprecipitation assay with nephelometric endpoint detection. IgG, IgA, C3 and C4 levels were significanty higher in patients with PV than in healty controls (p < 0.05). However, NK cell activity, serum Zn and IgM levels did not show significant differences between these two groups. There are changed immunological responses, which may play an important role in the pathogenesis of the disease. Many controversial results have been related to immunological parameters in psoriatic patients. Therefore, more detailed studies in this field need to be done to determine the relationship between psoriasis and the immune system.

Effect of phototherapy and urocanic acid isomers on natural killer cell function

Ultraviolet (UV) radiation suppresses a variety of immune responses but it is uncertain whether this action contributes to the effectiveness of phototherapy. Urocanic acid (UCA) has been proposed as a mediator of the immunologic effects of UV. On exposure the naturally occurring trans-isomer of UCA in the skin changes into the cis-isomer, which has been demonstrated to mimic many of the immunomodulatory effects of UV irradiation. Natural killer (NK) cells play an important role in several immunologic processes and published evidence indicates that their activity is altered by UV irradiation. To ascertain the effect on NK cells of phototherapy used in the treatment of psoriasis, modulation of NK activity in psoriatic patients undergoing broad-band UVB, narrow-band UVB, or psoralen plus (PUVA) regimens was examined. This was compared with NK cell activity in psoriatic patients treated with topical coal tar and in normal subjects receiving broad band UVB. The NK cell activity of psoriatic and normal subjects was the same over a wide range of effector to target cell ratios. Almost all patients undergoing phototherapy exhibited depressed NK cell activity during or after irradiation, although the timing of the depression varied between the lamps used and may be related to dose. However, patients treated with topical coal tar showed unchanged NK cell activity throughout the therapy. The effect of UCA isomers on NK cell activity in vitro was also determined. It was found that cis-UCA induced a dose-dependent suppression of NK cell activity in both patients and normal subjects, whereas trans-UCA had hardly any effect in either group. Thus it is possible that there may be a correlation between cis-UCA formation in the epidermis and the modulation of NK cell activity that occurs during phototherapy.

Immunologic mechanisms in psoriasis

This review presents evidence for the immunopathogenesis of psoriasis. T lymphocytes with human lymphocyte antigen (HLA)-DR molecules and receptors for interleukin 2 were found in the dermis of psoriatic plaques, suggesting the presence of activated T cells in these lesions. Keratinocytes in active plaques demonstrated HLA-DR molecules on their surfaces. These immunologic abnormalities were reversible with medical therapy. Keratinocyte HLA-DR expression was associated with an increased incidence of psoriatic arthritis. We propose that HLA-DR + keratinocytes and Langerhans cells in plaques could activate dermal T cells directly in an autologous mixed leucocyte/epithelial cell reaction. Alternatively, they could present an unknown autologous or exogenous antigen to T lymphocytes. T cell activation would then lead to the release of mediators of inflammation, and possibly of epidermal growth factors. This hypothesis also provides an explanation for the chronicity of psoriasis. Most of the therapies used to treat psoriasis suppress cellular immune function and inflammation. These include ultraviolet irradiation, cyclosporine, corticosteroids, methotrexate, anthralin, and retinoids.

Relaxation therapies in the treatment of psoriasis and possible pathophysiologic mechanisms

Psychologic factors play a role in many dermatologic disorders, giving rise to the possible use of psychotherapeutic modalities in treatment. Regarding psoriasis, emotional factors have a strong correlation with onset and flare-ups. The psychophysiologic mechanisms involved are not known; however, stress and its effect on the autonomic nervous system and the immune system may play a significant role in the onset and course of psoriasis. Relaxation and mere suggestion also affect the autonomic nervous system and the immune system and therefore may affect the course of the skin disorder. A few case studies have documented successful treatment of psoriasis with hypnosis and biofeedback. Further study of this process is needed, and the role of stress in dermatologic diseases must always be given consideration.

Electron microscopic features in generalized pustular psoriasis

Basal keratinocyte herniations (BKH) have been used as markers of psoriatic activity. Abnormal multipolypoid forms herniating through large gaps in the basal lamina have been found to characterize biopsies from psoriatic patients with concomitant alpha 1-antitrypsin deficiency, and appear to be a marker of excessive proteolytic activity. The finding of similar multipolypoid BKH in patients with generalized pustular psoriasis of the von Zumbusch variety (but not in patients with psoriasis vulgaris), in the absence of concomitant alpha 1-antitrypsin deficiency, would support the concept of the presence of large amounts of proteolytic enzymes in the dermis of patients with this syndrome. The large proportion of BKH directly associated with dermal neutrophils, and the presence of clusters of high-density BKH overlying collections of dermal neutrophils, suggests that neutrophilic proteases are largely responsible for BKH formation in patients with this syndrome.

Marked increase in the frequency of psoriatic arthritis in psoriasis patients with HLA-DR+ keratinocytes

Immunocytochemical studies with a monoclonal anti-HLA-DR antibody were performed on skin sections and keratinocyte (KTC) suspensions obtained from suction blisters of active psoriatic plaques. HLA-DR+ KTCs were found in the plaques of 23 of 38 patients with active psoriasis. Of these 23, 16 had clinical findings typical of psoriatic arthritis (PA); none of the 15 patients who lacked HLA-DR+ KTCs had PA. Although KTC HLA-DR expression was more prevalent in patients with severe skin disease, 7 of the 23 patients with HLA-DR+ KTCs in active psoriatic plaques had mild skin disease; 4 of these 7 had PA. Nail pitting or duration of skin disease did not account for increased incidence of PA in patients with HLA-DR+ KTCs. All psoriasis patients with arthritis received nonsteroidal antiinflammatory drug therapy; 14 received additional therapy directed primarily to the cutaneous manifestations of psoriasis. Nine of these noted arthritis improvement with concurrent skin response; however, in 5 patients, arthritis activity increased, despite improvement of the cutaneous disease. Two other patients, treated with methotrexate, also had concurrent skin and joint improvement. These data suggest that psoriasis patients with HLA-DR+ KTCs are at increased risk for the development of associated arthritis.

Expression of HLA-DR molecules by keratinocytes, and presence of Langerhans cells in the dermal infiltrate of active psoriatic plaques

Immunoperoxidase staining of skin sections and immunofluorescence analysis of keratinocyte suspensions obtained from suction blisters of psoriatic plaques were performed using an mAb, Josh 524.4.1, and Fab'2 fragments of a rabbit antiserum, both of which are directed against nonpolymorphic determinants of HLA-DR molecules. HLA-DR+ keratinocytes were present in plaques, but not normal-appearing skin, from a significant portion of patients with active psoriasis. Double-labelling immunofluorescence experiments with either the monoclonal or polyclonal anti-HLA-DR antibody, in conjunction with the mAb OKT6, which identifies DR+ Langerhans cells, demonstrated that HLA-DR molecules were present on OKT6- keratinocytes. The dermal infiltrate of psoriatic plaques contained T cells expressing the activation antigens, IL-2 receptor (Tac) and HLA-DR, as well as macrophages and OKT6+ cells. There was little difference in the characteristics of the dermal infiltrate between the lesions with or without HLA-DR+ keratinocytes. OKT6+ presumptive Langerhans cells were also found in the dermal infiltrates of patients with lichen planus, contact dermatitis, spongiotic dermatitis, erythema multiforme, basal and squamous cell carcinoma. Studies of keratinocyte suspensions showed that 7-84% of keratinocytes were HLA-DR+. Flow cytometry experiments showed that keratinocytes at all stages of differentiation were HLA-DR+. However, the stem cell-enriched population contained the highest proportion of HLA-DR+ cells. HLA-DR expression by keratinocytes correlated with disease activity. The expression was reversible with successful medical therapy. HLA-DR+ keratinocytes may activate T cells directly or may present an as yet unknown antigen to T cells. These studies provide further support for the hypothesis that immunological mechanisms play an important role in the pathogenesis of psoriasis.

Defective natural-killer- and killer-cell activity associated with increased polymorphonuclear leukocyte adherence in psoriasis

Patients (n = 45) with psoriasis vulgaris were studied for natural killer (NK) cell activity and antibody-dependent cell cytotoxicity (ADCC) of their peripheral blood mononuclear cells against K-562 and L1210 target cells, respectively. Simultaneously, the studies were performed on the adherence to human endothelium of polymorphonuclear leukocytes (PMN) from various forms of the disease. Mean values of NK-cell activity in psoriasis vulgaris, as a whole, and mean values of ADCC in male patients were significantly lower than in a group of healthy controls. This decrease was most pronounced in patients with the active form of the disease, in whom in vitro PMN adherence to human endothelium was found to be increased. Neutrophils from both patients with active psoriasis and healthy individuals were capable of reducing NK-cell activity of normal human mononuclear cells.