The development of manifest psoriatic lesions is linked with the invasion of CD8+ T cells and CD11c+ macrophages into the epidermis

Koebner response was studied in 35 psoriatic patients. Two punch biopsies per patient were taken from non-lesional psoriatic skin before, and 6 h, 2 days, 7 days, 14 days and 21 days after, tape stripping. Alterations in the numbers of CD1+ Langerhans cells, CD4+ and CD8+ T cells and CD11c+ macrophages were mapped morphometrically. Results were compared with lesional and non-lesional psoriatic skin, and control skin. Nine of 35 patients were Koebner-positive. No statistically significant differences were noted between non-lesional psoriatic and control skin. CD4+ T cells increased in number 2 days after trauma in both the epidermis and the dermis, whereas epidermal CD8+ T cells and CD11c+ macrophages increased only in the Koebner-positive lesional skin after 7 days. The changes in lesions induced by tapestripping resembled those seen in lesional psoriatic skin (mature plaques). The number of CD1+ cells increased in mature psoriatic lesions only. It seems possible that trauma per se stimulates the accumulation of CD4+ T cells at the site of injury, but the development of manifest psoriatic lesions correlates with invasion of CD8+ T cells and CD11c+ macrophages into the epidermis.     

Mechanisms of cyclosporine A inhibition of antigen-presenting activity in uninvolved and lesional psoriatic epidermis

To elucidate how cyclosporine A affects antigen-presenting cell subsets and their function in human skin, we studied patients with psoriasis undergoing a therapeutic trial of cyclosporine A. Immunologic parameters abnormal in psoriatic epidermis were evaluated before and early in the course of therapy. We quantitated function and numbers of skin biopsy-derived epidermal cells with potential antigen-presenting cell (APC) activity. The antigen-presenting capacity of epidermal cells from normal-appearing skin to activate allogeneic T cells was profoundly inhibited (81% decrease) 7 d after the onset of therapy (p less than 0.05). Thus, cyclosporine A therapy inhibited T-cell activation mediated by Langerhans cells in uninvolved skin. By contrast, in lesional skin epidermal allo-antigen presenting activity was only partially inhibited at this early time point (55 +/- 7% decrease) (p less than 0.01, n = 8). The percentage decrease in allo-antigen-presenting cell activity correlated with reduced clinical activity of the lesions, r = 0.84. In three patients also examined at 14 d, we found an additional 42 +/- 5% decrease between day 7 and 14. Decreased allo-antigen-presenting activity in lesional skin was not associated with a decrease in the number of CD1+ Langerhans cells or epidermal cell release of detectable amounts of cyclosporine A or other soluble factors that abrogate T-cell alloreactivity. The time course and degree of inhibition of antigen-presenting capacity within involved psoriatic skin correlated best with a significant (p less than 0.01) reduction in non-Langerhans cell DR+ leukocytes (from 3.0 +/- 1.2% to 1.0 +/- 0.6% at day 7) (r = 0.71). Cyclosporine A therapy was associated with a rapid and complete loss of HLe1-DR+ keratinocytes (94% decrease at 7 d) in lesional skin despite the skin still being quite involved with psoriasis at this point and antigen-presenting cell activity being only 60% reduced. In conclusion, cyclosporine A interferes with T-cell activation by human epidermis through at least two mechanisms: 1) in uninvolved skin, rapid inhibition of Langerhans cell-mediated activation of T cells, and 2) in lesional skin, delayed inhibition of antigen-presenting activity which appears to correlate with the time course and level of reductions in non-Langerhans cell DR+ leukocytes. The antigen-presenting activity of the latter cells appears to be cyclosporine A resistant. In psoriatic lesions, early and complete loss of DR expression on lesional keratinocytes during cyclosporine A therapy is likely due to decreased lesional T-cell lymphokine production critical for keratinocyte DR expression.(ABSTRACT TRUNCATED AT 400 WORDS)     

Cutaneous T-cell lymphoma lesional epidermal cells activate autologous CD4+ T lymphocytes: involvement of both CD1+OKM5+ and CD1+OKM5- antigen-presenting cells

Cutaneous T-cell lymphoma is characterized by infiltration of the skin by activated CD4+ T lymphocytes. The mechanism by which these T lymphocytes achieve and maintain their activated state is unknown. Antigen-specific activation of T lymphocytes is dependent upon antigen-presenting cells which express HLA-DR class II major histocompatibility complex molecules, such as epidermal Langerhans cells. In addition to CD1+DR+ Langerhans cells, cutaneous T-cell lymphoma lesional epidermis contains major histocompatibility complex class II positive non-Langerhans cell populations, including CD1+OKM5+ bone-marrow-derived cells and DR+ keratinocytes. We asked whether any of these epidermal cell populations demonstrate capacity to activate T lymphocytes. Various numbers of epidermal cells from uninvolved and involved cutaneous T-cell lymphoma plaques were therefore used to stimulate autologous CD4+ and CD8+ T lymphocytes in the absence of exogenous antigen. Involved epidermal cells potently induced proliferation of CD4+ T lymphocytes (S.I. +/- SEM = 466 +/- 45). In contrast, uninvolved epidermal cells only induced background levels of proliferation (S.I. +/- SEM = 2 +/- 0.5, N = 8, p less than 0.01). Neither involved nor uninvolved epidermal cells were able directly to activate CD8+ lymphocytes. The capability of involved epidermal cells to activate CD4+ T lymphocytes was dependent upon CD1+DR+ leukocytes and not DR+ keratinocytes, because depletion of either HLA-DR+, CD1+ or HLe1+ epidermal cells totally abrogated the T-lymphocyte proliferation. Interestingly, on a cell per cell basis CD1+DR+ cells obtained from involved skin, demonstrated relative to CD1+DR+ cells from uninvolved skin, enhanced capacity to activate CD4+ T lymphocytes. Furthermore, CD1+OKM5+ cells from involved epidermis stimulated autologous CD4+ T lymphocytes. This indicates that a unique hitherto undescribed CD1+OKM5+ epidermal antigen-presenting cell population may participate in T-lymphocyte activation. These findings provide support for the concept that the epidermal cells in cutaneous T-cell lymphoma patients, particularly the antigen-presenting cells, may contribute significantly to the activation of CD4+ malignant and/or non-malignant inflammatory T lymphocytes within the skin.     

Intraepidermal lymphocytes in psoriatic lesions are activated GMP-17(TIA-1)+CD8+CD3+ CTLs as determined by phenotypic analysis

The onset and persistence of psoriatic lesions are linked to the presence of an inflammatory infiltrate of CD3+ lymphocytes that includes CD4+ and CD8+ subsets. Since a primary susceptibility factor for psoriasis is the Class I HLA-Cw6 molecule, we set out to learn more about the features of the epidermal CD8+ lymphocytes. The markers tested were GMP-17, a cytotoxic granule protein found in activated cytotoxic lymphocytes (CTLs), and the alpha chain of the IL-2 receptor (CD25), a plasma membrane molecule found on activated T cells. Lymphocytes in lesional skin expressed the GMP-17 protein, whereas lymphocytes in non-lesional skin, resolving lesional skin and normal skin had little or no GMP-17. By flow cytometry analysis, lesional epidermal GMP-17+ cells were CD8+CD3+, with a subpopulation expressing the activation marker CD25+. Due to the abundance of activated GMP-17+CD8+CD3+ lymphocytes (the phenotype of activated cytotoxic cells) in psoriatic lesions compared to non-lesional and normal skin, we hypothesize that they are contributing directly to the psoriatic phenotype.     

Expression of the T-cell activation antigens CD27 and CD28 in normal and psoriatic skin

Activated T lymphocytes are thought to be involved in the pathogenesis of psoriasis. From studies with peripheral blood T lymphocytes it is known that T cells show a decrease in membrane expression of CD27 molecules during continuous antigenic stimulation. The T-cell activation molecule CD28 is thought to be involved in the transduction of an antigen-non-specific costimulatory signal. Therefore, in order to elucidate further the pathogenesis of psoriasis we studied the expression of CD27 and CD28, together with CD4, CD8 and CD45RA in this benign inflammatory dermatological disease. We used immunohistochemical techniques to determine absolute numbers of T lymphocytes and expression of these T-cell activation and T-subset-specific molecules in normal (n= 7), uninvolved perilesional (n= 7) and lesional psoriatic (n= 7) skin. We found that not only lesional but also clinically uninvolved perilesional skin showed an increased number of T cells. Further, immunohistochemical studies showed that CD27 is expressed by a minority of normal skin T cells, while in lesional psoriatic skin, expression was even lower, and almost absent in perilesional skin sections. In contrast to normal skin, both perilesional and lesional psoriatic skin contained no CD28 positive T cells. In lesional psoriatic skin, however, T cells showed predominantly the CD4 phenotype, while in perilesional skin CDS positive T cells were dominant. Two conclusions were reached: first, the absolute number of T cells, their CD27, CD28 and CD45RA expression, and the influx of CD8 positive T cells, indicate that perilesional psoriatic skin is different from normal and lesional psoriatic skin; and secondly, the data on CD27 and CD28 suggest that not only lesional but also perilesional psoriatic skin is subject to continuous antigenic stimulation, thus leading to decreased CD27 and CD28 expression on skin T cells.     

Psoriasis is characterized by accumulation of immunostimulatory and Th1/Th17 cell-polarizing myeloid dendritic cells

Myeloid dermal dendritic cells (DCs) accumulate in chronically inflamed tissues such as psoriasis. The importance of these cells for psoriasis pathogenesis is suggested by comparative T-cell and DC-cell counts, where DCs outnumber T cells. We have previously identified CD11c(+)-blood dendritic cell antigen (BDCA)-1(+) cells as the main resident dermal DC population found in normal skin. We now show that psoriatic lesional skin has two populations of dermal DCs: (1) CD11c(+)BDCA-1(+) cells, which are phenotypically similar to those contained in normal skin and (2) CD11c(+)BDCA-1(-) cells, which are phenotypically immature and produce inflammatory cytokines. Although BDCA-1(+) DCs are not increased in number in psoriatic lesional skin compared with normal skin, BDCA-1(-) DCs are increased 30-fold. For functional studies, we FACS-sorted psoriatic dermal single-cell suspensions to isolate these two cutaneous DC populations, and cultured them as stimulators in an allogeneic mixed leukocyte reaction. Both BDCA-1(+) and BDCA-1(-) myeloid dermal DC populations induced T-cell proliferation, and polarized T cells to become T helper 1 (Th1) and T helper 17 (Th17) cells. In addition, psoriatic dermal DCs induced a population of activated T cells that simultaneously produced IL-17 and IFN-gamma, which was not induced by normal skin dermal DCs. As psoriasis is believed to be a mixed Th17/Th1 disease, it is possible that induction of these IL-17(+)IFN-gamma(+) cells is pathogenic. These cytokines, the T cells that produce them, and the inducing inflammatory DCs may all be important new therapeutic targets in psoriasis.     

Activation of dendritic antigen-presenting cells expressing common heat shock protein receptor CD91 during induction of psoriasis

BACKGROUND: Psoriasis is a common and chronic relapsing inflammatory skin disorder. Although a role for T cells in mediating the induction and maintenance of psoriatic lesions is well established, mechanisms responsible for activation of T cells by antigen-presenting cells (APCs) during disease relapse are poorly understood. OBJECTIVES: (i) To determine whether expression of the common heat shock protein (HSP) receptor CD91 correlated with development of psoriasis in a mouse model of psoriasis, (ii) to characterize the lesional cells on which CD91 was expressed, and (iii) to investigate whether CD91+ cells in psoriasis showed signs of activation. METHODS: Two systems were used in order to study the above-mentioned objectives: (i) skin biopsies taken directly from patients with psoriasis (either psoriatic plaques or symptomless prepsoriatic skin) or from healthy donors, respectively, or (ii) (human) skin biopsies collected during development of psoriasis using a novel xenograft mouse model of psoriasis. The skin samples were then either processed for analysis by light microscopy, or labelled with fluorochrome-conjugated antibodies and analysed by confocal laser scanning microscopy. RESULTS: We observed a markedly increased number of CD91+ cells which paralleled development of new psoriatic lesions in the psoriasis mouse model and in established psoriatic plaques compared with symptomless prepsoriatic or healthy skin. Morphology as well as cell-specific markers showed that CD91 was predominantly expressed by dermal dendritic APCs characterized by activation of nuclear factor-kappaB signalling and the presence of tumour necrosis factor-alpha, an important proinflammatory cytokine in the immunopathogenesis of psoriasis. In addition, HSP70, a ligand for CD91, was increased in keratinocytes in close vicinity to CD91-bearing APCs in psoriatic lesions. CONCLUSIONS: These findings indicate massive presence of CD91+ dendritic cells juxtaposed to lesional keratinocytes expressing HSP70, and suggest a novel pathophysiological pathway and therapeutic target for this chronic inflammatory skin disease.     

UM4D4+ (CDw60) T cells are compartmentalized into psoriatic skin and release lymphokines that induce a keratinocyte phenotype expressed in psoriatic lesions

UM4D4 (CDw60), the surface molecule of a novel antigen-independent T-cell activation pathway, was found to be highly expressed on lesional psoriatic T cells. To examine whether UM4D4 represents a T-cell activation pathway for psoriatic T cells, a T-cell line was initiated from an acute skin lesion and cloned by limiting dilution. Clonality was verified by analysis of T-cell receptor gene rearrangement. All T-cell clones tested, whether CD4+2H4+CD8-, CD4+2H4-CD8-, or CD4-CD8+CD11b-, expressed UM4D4 and were activated by the monoclonal antibody anti-UM4D4. Lesional psoriatic T-cell clones were heterogeneous in the degree of anti-UM4D4-induced proliferation and in their production of IL-2 and gamma-interferon. Lymphokines released by anti-UM4D4 activation were capable of inducing ICAM-1 and HLA-DR expression on cultured normal keratinocytes. Thus, the high expression of UM4D4 on T-cells in psoriatic skin provides an alternative mechanism for T-cell activation that may be operative in the psoriatic lesional milieu. Indeed, activation of lesional T-cells through the UM4D4 molecule resulted in release of lymphokines that directly induced keratinocytes to express a phenotype displayed in psoriatic skin lesions.     

CD8+ cell changes in psoriasis associated with roxithromycin-induced clinical improvement

We have shown that T cell receptor BV2- and BV8-bearing CD8+ cells are decreased in the peripheral blood of psoriatic patients, while T cells possessing these BVs accumulate in psoriatic lesions. T cells homing to skin express cutaneous lymphocyte-associated antigen (CLA), and bacterial superantigens that trigger psoriasis promote this expression. Roxithromycin has immunomodulatory potency and its effectiveness for psoriasis has been proposed. Therefore, we monitored BV usage and alteration of superantigen-promoted CLA expression in circulating CD8+ cells of psoriatics before and after roxithromycin therapy. After roxithromycin treatment, circulating BV2- and BV8-bearing CD8+ cells were increased and CD8+ cells exhibited reduced expression of CLA when stimulated in vitro with bacterial superantigens. It is suggested that roxithromycin downregulates augmented expression of CLA by CD8+ cells, thereby suppressing their skin-homing and elevating the numbers of circulating BV2- and BV8-positive CD8+ cells. Such events may be included in part in the improvement of psoriasis with roxithromycin.     

Identification of lesional CD4+ CD25+ Foxp3+ regulatory T cells in Psoriasis

BACKGROUND: Depletion of CD4+ CD25+ Foxp3+ naturally occurring regulatory T cells (T(reg)) induces autoimmune phenomena. These cells have not yet been fully characterized in the skin of psoriatic patients. OBJECTIVES: To prove that the Zenon immunofluorescent labeling technique is suitable for the demonstration of co-localization of T-cell markers and in particular to show the distribution of T(reg) in psoriatic skin. METHODS: In biopsies derived from normal and psoriatic skin, CD4+ CD25+, CD4+ CD45RO+, CD8+ CD25+, CD8+ CD45RO+ and CD4+ CD25+ Foxp3+ cells in the dermis and in the epidermis were immunophenotyped, using a quantitative immunofluorescent labeling technique (Zenon), analyzed and compared using image analysis. RESULTS: The immunofluorescent labeling technique was shown to be an easy and reliable tool to demonstrate co-localization of T-cell markers. In psoriasis, all pathogenic T-cell subsets (CD4+ CD25+, CD4+ CD45RO+, CD8+ CD25+ and CD8+ CD45RO+ cells) were significantly increased in the dermis and in the epidermis, as compared to normal skin (all p < 0.05). Using this labeling technique we were able to reveal CD4+ CD25+ Foxp3+ T(reg) in psoriatic dermis, but not in the dermis of normal skin (p < 0.0001). CONCLUSIONS: The Zenon immunofluorescence technique in combination with image analysis is suitable for the demonstration of co-localization of T-cell markers in tissue. Increased numbers of pathogenic T cells (CD4+ CD25+, CD4+ CD45RO+, CD8+ CD25+ and CD8+ CD45RO+) were shown in the dermis and epidermis, whereas CD4+ CD25+ Foxp3+ T(reg) were identified in psoriatic skin with a predilection for the upper dermis.     

CD70-CD27 interaction augments CD8+ T-cell activation by human epidermal Langerhans cells

Human cutaneous dendritic cells (DCs) from epidermal and dermal compartments exhibit functional differences in their induction of CD4+ T-cell and humoral immune responses; however, differences in the regulation of memory CD8+ T-cell responses by human skin DCs remain poorly characterized. We tested the capacity of human Langerhans cells (LCs) and dermal dendritic cells (DDCs) to induce antigen-specific cytokine production and proliferation of memory CD8+ cells. Although tumor necrosis factor-α-matured human DCs from both epidermal and dermal compartments showed efficient potential to activate CD8+ cells, LCs were constitutively more efficient than DDCs in cross-presenting CD8+ epitopes, as well as direct presentation of viral antigen to Epstein-Barr virus-specific CD8+ T cells. LCs showed greater expression of CD70, and blockade of CD70-CD27 signaling demonstrated that superiority of CD8+ activation by epidermal LC is CD70 dependent. This CD70-related activation of CD8+ cells by LCs denotes a central role of LCs in CD8+ immunity in skin, and suggests that regulation of LC CD70 expression is important in enhancing immunity against cutaneous epithelial pathogens and cancer.     

Ultraviolet-B irradiation decreases IFN-gamma and increases IL-4 expression in psoriatic lesional skin in situ and in cultured dermal T cells derived from these lesions

Type 1 cytokine producing T cells play an important role in the pathogenesis of psoriasis. Ultraviolet-B (UVB) irradiation is effective in the treatment of this disease. In normal skin, UVB causes a change in dermal microenvironment, leading to a decrease of IFN-gamma expressing type 1 T cells and a concurrent increase of IL-4 expressing type 2 T cells. The aim of this study was to show whether UVB irradiation causes a like-wise shift of type 1 and type 2 responses in psoriatic skin. For this purpose, biopsies were obtained from the lesional skin of psoriatic patients before, 2 days and 14 days after a single exposure to 4 MED UVB. Sections from these biopsies were immunostained (CD3, IFN-gamma and IL-4) or RNA was extracted and analyzed for the expressions of IFN-gamma and IL-4 by PCR. In addition, primary cultures of T cells from dermal cell suspensions were stained intracellularly for IFN-gamma and IL-4 expression and CD4+ and CD8+ T subsets were analyzed by flow cytometry. IFN-gamma was abundantly expressed in situ before irradiation and decreased in all patients after UVB irradiation, whereas IL-4 expression was variably expressed before irradiation and increased in different degrees after irradiation. Cytokine mRNA expressions determined by PCR showed a clear decrease of IFN-gamma and increase of IL-4 following UVB irradiation. Both CD4+ and CD8+ dermal T cells were found to produce less IFN-gamma and more IL-4 following UVB irradiation as determined by flow cytometry. Decrease in IFN-gamma expression and increase in IL-4 expression of dermal T cells in psoriatic lesions after UVB irradiation may lead to decrease in local immunoreactivity. These changes could be part of the therapeutic effects of UVB on psoriasis.     

Increased circulating skin-homing cutaneous lymphocyte-associated antigen (CLA)+ type 2 cytokine-producing cells, and decreased CLA+ type 1 cytokine-producing cells in atopic dermatitis

BACKGROUND: Skin-homing T cells are characterized by expression of cutaneous lymphocyte-associated antigen (CLA). Few data are available on the frequency of circulating CLA+ cytokine-producing T cells in atopic dermatitis (AD) patients. OBJECTIVES: We aimed to investigate cytokine synthesis capability vs. CLA expression in phorbol myristate acetate and ionomycin-stimulated, secretion-inhibited peripheral blood T cells of AD patients compared with healthy subjects and psoriatic patients. METHODS: Multiparameter flow cytometry was used. RESULTS: The expression of CLA among CD4+ T cells was significantly elevated in AD patients compared with healthy subjects and psoriatic patients, whereas there was no significant difference between each group in CLA expression among CD8+ T cells. The frequency of interleukin (IL)-4- and IL-13-producing cells in AD patients was significantly higher than in healthy subjects (in both CD4+ and CD8+ T-cell subsets) and psoriatic patients (in CD4+ T cells). In contrast, the frequency of interferon (IFN)-gamma-producing cells was significantly reduced in AD patients, among both CD4+ and CD8+ T cells, compared with healthy subjects and psoriatic patients. Moreover, in AD patients, the frequency of IL-4- and IL-13-producing cells was remarkably increased among the CLA+ subset (in both CD4+ and CD8+ T cells), whereas the frequency of IFN-gamma-producing cells was decreased in the CLA+ subset (in CD4+, but not in CD8+ T cells). CONCLUSIONS: These results provide evidence for the expansion of skin-homing type 2 cytokine-secreting T cells, associated with a reduction in skin-homing type 1 cytokine-producing T cells, in peripheral blood of AD patients.     

Preferential expression of alphaEbeta7 integrin (CD103) on CD8+ T cells in the psoriatic epidermis: regulation by interleukins 4 and 12 and transforming growth factor-beta

BACKGROUND: Intraepidermal T lymphocytes are a critical element for sustaining the lesional pathology of psoriasis. Integrin alphaEbeta7 (CD103), a ligand for E-cadherin, may play a role in the localization of pathogenic T cells within the epidermis of psoriatic lesions. However, little information is available regarding alphaEbeta7 expression on intraepidermal T cells in psoriasis. OBJECTIVES: To examine alphaEbeta7 expression on intraepidermal T cells in psoriatic lesions and the regulation of alphaEbeta7 expression on T cells in response to cytokines. METHODS: T-cell expression of alphaEbeta7 was examined by immunohistochemistry and flow cytometry. In vitro regulation of alphaEbeta7 expression on CD4+ or CD8+ T cells purified from peripheral blood of healthy donors was also examined. RESULTS: Immunohistochemical staining revealed expression of alphaEbeta7 on a greater proportion of epidermal T cells than dermal T cells. Nearly 30% of intraepidermal CD4+ T cells were found to express alphaEbeta7 on flow cytometry, whereas more than 80% of intraepidermal CD8+ T cells expressed this integrin. In contrast, few T cells expressed alphaEbeta7 in the peripheral blood of psoriatic patients. The in vitro culture experiment confirmed that alphaEbeta7 was preferentially expressed on CD8+ T cells after stimulation with anti-CD3 monoclonal antibodies. Addition of transforming growth factor-beta and interleukin-4 upregulated alphaEbeta7 expression on T cells, whereas interleukin 12 downregulated this. Furthermore, alphaEbeta7 expression on established memory CD8+ T cells was not so reversible as that on CD4+ T cells. CONCLUSIONS: Preferential and stable expression of alphaEbeta7 on CD8+ T cells may be involved in the lesional pathology of psoriasis.     

Influence of psoriatic peripheral blood CD4+ T and CD8+ T lymphocytes on C-myc, Bcl-xL and Ki67 gene expression in keratinocytes

T cells play a role in the hyperproliferation of keratinocytes, however, direct evidence on what is the main mechanism and which T-cell subset is central is still lacking. Our aim was to elucidate the role and mechanism of CD4+T and CD8+ T lymphocytes in the immunopathogenesis of lesion hyper-proliferation in psoriasis. T cell and CD4+T and CD8+ T cell subpopulations were isolated by immunomagnetic methods from peripheral blood of psoriatic patients and healthy volunteers. Keratinocytes from foreskins were incubated in the absence or presence of T cells and T cell subpopulations for 72 h. The expression of c-Myc, Bcl-xL and Ki67 proteins in keratinocytes were detected by immunohistochemical staining, and then IL-4, IL-8 and IFNgamma level in the supernatant was determined by respective ELISA. T cells of psoriatic origin induced keratinocytes to overexpress C-myc and Ki67 proteins with high amounts of IL-8 and IFN-gamma in the supernatant, while the T cells of normal origin did not. Furthermore, there was a difference in keratinocyte response to CD4+ T cells and CD8+ T cells from psoriatic patients. CD4+ T cells can secrete much higher levels of IL-8 and IFN-gamma and induced much stronger C-myc and Ki67 expression in keratinocytes, compared with CD8+ T cells. We concluded that psoriatic peripheral blood T cells and the T cell subpopulation could induce keratinocytes to over-express pro-proliferation proteins probably by secreting Th1 cytokines. T cells, especially the CD4+ T cell subpopulation, play an important role in the immunopathogenesis of lesion hyper-proliferation in psoriasis.     

Epidermal dendritic cells in psoriasis possess a phenotype associated with antigen presentation: in situ expression of beta 2-integrins.

BACKGROUND: Epidermal dendritic cells (DCs) isolated from psoriasis possess greatly enhanced T lymphocyte-activating properties compared with DCs from normal skin, suggesting that DCs in psoriasis express surface antigens crucial for antigen presentation. These include beta 2-integrins and intercellular adhesion molecule (ICAM)-1. OBJECTIVE: Our purpose was to determine DC phenotype in psoriatic compared with normal epidermis with respect to these molecules. METHODS: Tissue sections were single labeled with a peroxidase antiperoxidase (PAP) immunohistochemical technique and double labeled where necessary with a combination of a PAP and an alkaline phosphatase-anti-alkaline phosphatase technique. RESULTS: In psoriatic compared with normal skin, decreased numbers of DCs expressed CD1a (p less than 0.05), whereas increased numbers of DCs expressed class II major histocompatibility antigens (p less than 0.05). In normal skin positive staining for CD18 was not observed, whereas in psoriasis both CD1a+ and CD1a- DCs expressed beta 2-integrins, LFA-1 (CD11a/CD18), and gp 150/95 (CD11c/CD18). DCs in atopic dermatitis and lichen planus were also found to express beta 2-integrins. Neither MAC 1 (CD11b/CD18) nor ICAM-1 was observed on DCs. CONCLUSION: These data are consistent with either migration of dendritic antigen-presenting cells into the epidermis or in situ cytokine modulation of Langerhans cell phenotype in inflamed skin. Furthermore, they indicate that epidermal DCs in psoriasis and other cutaneous inflammatory diseases express molecules that are known to be crucial for Langerhans cell-driven T-cell activation in vitro.     

Calcipotriol inhibits the proliferation of hyperproliferative CD29 positive keratinocytes in psoriatic epidermis in the absence of an effect on the function and number of antigen-presenting cells

The aim of this study was to elucidate some of the possible mechanisms of action of the vitamin D analogue calcipotriol in vivo . Calcipotriol is finding increasing use in the treatment of psoriasis, but the primary target cell in vivo has not yet been identified. We treated psoriatic patients and healthy volunteers with calcipotriol and placebo ointment for 4 and 7 days, and obtained epidermal cell suspensions from treated areas. Epidermal cells were cocultured with autologous T cells, isolated from peripheral blood, in the absence or the presence of a classical antigen or a superantigen. In both psoriatic and normal skin, calcipotriol treatment did not alter the capacity of epidermal antigen-presenting cells to stimulate the proliferation of autologous T cells, either in the absence or in the presence of exogenous antigen. Epidermal cell suspensions were analysed further by staining for infiltrating leucocytes (CD45+) and Langerhans cells (CD1a+). Flow cytometric analyses showed that calcipotriol did not alter the number of CD45+ cells or Langerhans cells in psoriatic skin. These results indicate that calcipotriol does not alter either the number or the function of epidermal antigen-presenting cells in psoriatic epidermis. In contrast, we found that calcipotriol significantly inhibited the proliferation of epidermal cells isolated from psoriatic skin after in vivo treatment, as determined by propidium iodide staining and flow cytometry. More specifically, we stained for CD29+ keratinocytes and found an even more significant reduction in proliferative capacity. This cell type contains the population of hyperproliferative keratinocytes in psoriatic epidermis. In conclusion, calcipotriol seems to act via an inhibitory effect on hyperproliferative basal keratinocytes of psoriatic epidermis, rather than via an effect on infiltrating leucocytes, including antigen-presenting cells.     

CD69+T细胞在银屑病皮损中的表达及其临床意义

目的 探讨银屑病患者皮肤CD69+T细胞的表达及其与疾病活动性的关系.方法 免疫组化检测31例银屑病患者皮损和非皮损中CD69+T细胞在皮肤中的表达,与6例健康人进行对照.结果 CD69+T细胞主要分布于皮肤真皮.31例银屑病患者皮损和非皮损的真皮中,CD69+T细胞分别为(35.16±12.67)％和(8.70±3.29)％,皮损明显高于非皮损(t=12.5,P＜0.01).6例健康人对照皮肤中CD69+T细胞(8.71±2.55)％,明显低于银屑病皮损(t=5.03,P＜ 0.01),与非皮损相比,差异无统计学意义(t=0.05,P＞ 0.05).20例急性期与1 1例稳定期银屑病患者皮损中CD69+T细胞分别为(40.89±10.31)％和(24.46±9.49)％,急性期明显高于稳定期(t=0.36,P＜ 0.01).结论 银屑病患者皮损中CD69+T细胞表达增高,与疾病的活动性有关.     

Human 6-sulfo LacNAc (slan) dendritic cells are a major population of dermal dendritic cells in steady state and inflammation

Background. The immune system of the skin has a network of resident dendritic cells (DCs) consisting of epidermal Langerhans cells and various subsets of dermal DCs. We recently reported on a new population of dermal DCs, called slan (6‐sulfoLacNAc+) DCs, which have a potent capacity to stimulate Th17/Th1 T‐cell responses. Aim. To understand the characteristics of slanDCs as a new population of dermal DCs in the context of other DC populations in healthy and psoriatic skin. Methods. We immunofluorescently stained skin samples from healthy controls and from patients with psoriasis. Results. Staining healthy skin for DCs showed that slanDCs (CD1a? CD1c? CD11c? CD14? CD163?) were present at a similar frequency to that of CD1c+ CD11c+ CD1a+ CD14? CD163? dermal DCs, which have previously been regarded as the major population of resident DCs. In psoriatic skin, the frequency of slanDCs and CD1c+ DCs was doubled, and the slanDCs expressed CD11c. In‐depth analysis of DCs in psoriatic skin by four‐colour immunofluorescence analysis showed that the pool of CD11c+ cells could be further subdivided into CD11c+ CD14+ CD163? DCs and CD11c+ CD163+ CD14+ macrophages. Conclusion. SlanDCs, initially described as large population of proinflammatory DCs in blood, are a novel and major part of the resident dermal myeloid DC system in both healthy and inflamed skin.     

The role of the immune system in the pathogenesis of psoriasis

Psoriatic involved skin contains an increased number of activated T cells. The mechanism through which these T cells achieve and maintain their activated state is unknown, and both antigen-dependent and -independent mechanisms may contribute. Recently a novel pathway of antigen-independent T-cell activation has been described. This pathway is identified by a monoclonal antibody that binds to a T-cell membrane surface molecule termed "UM4D4.". This molecule is expressed on a minority (20%) of psoriatic peripheral blood T cells but on a majority (75%) of the T cells in lesional skin. Thus, UM4D4 could play a role in antigen-independent T-cell activation in psoriasis. Indeed the monoclonal antibody anti-UM4D4 consistently induces proliferation of psoriatic UM4D4+ T-cell clones. The activity of antigen-dependent pathways are also enhanced in psoriatic epidermis in as much as involved skin relative to uninvolved skin contains an increased number and function of antigen-presenting cells. Upon activation, the lesional T cells release lymphokines. Central to the immune hypothesis of psoriasis is that some of these T-cell lymphokines act on keratinocytes to induce changes characteristic of psoriasis. Indeed lymphokines from lesional psoriatic T-cell clones directly alter in vitro keratinocyte phenotype through induction of intercellular adhesion molecule-1 (ICAM-1) and HLA-DR cell-surface expression. Furthermore, the lymphokines also enhance keratinocyte growth. These data suggest a critical role for the immune system in the pathogenesis of psoriasis.