Immune-associated surface markers of human keratinocytes

Psoriatic keratinocytes prime neutrophils for an overproduction of superoxide anions

Psoriatic plaques result from an abnormal proliferation of keratinocytes associated with the local presence of T lymphocytes and neutrophils. The exact role of neutrophils in psoriatic lesions remains unclear. The present investigation was aimed at deciphering the capacity of psoriatic keratinocytes to alter in vitro functions of neutrophils. Blood neutrophils from healthy donors were incubated with psoriatic (PK) or healthy keratinocytes (HK) with and without IL-2-activated healthy T lymphocytes. The study was focussed on neutrophil capacity of adherence, viability and superoxide anion production. PK or HK with or without T lymphocytes similarly augmented neutrophil viability after 48 h of co-incubation. PK or HK did not directly activate the superoxide production by neutrophils. However, they both primed neutrophils for an increased fMLF-induced production of superoxide, an effect enhanced by the presence of T lymphocytes. PK were 1.5-fold more efficient than HK to augment this superoxide production. PK cultured with T lymphocytes induced the adhesion of neutrophils 4.7 times more efficiently than HK. The adherence of neutrophils was mediated through ICAM-1, LFA-1 and Mac-1, independently of bioactive lipids. The effects of PK and HK on neutrophil viability and priming were independent of direct cellular contact. In conclusion, keratinocytes can impact neutrophils by increasing their lifespan, and by priming them to overproduce superoxide. PK are more efficient than HK in priming neutrophils, an effect enhanced by T lymphocytes. These results indicate that neutrophils could contribute to psoriasis pathogenesis partly through their pathological interactions with PK.

Expression of CD13/aminopeptidase N and CD10/neutral endopeptidase on cultured human keratinocytes

Keratinocytes actively participate in immune response and inflammation by secreting cytokines and chemokines. Membrane-bound peptidases serve as negative loop in controlling concentration of peptide signalling molecules. Recently, they have also been proposed as additional mechanism of cell-to-cell interaction and as signalling molecules. In this study, we examined expression of two membrane-bound peptidases: aminopeptidase N (APN; EC 3.4.11.2; CD13) and neutral endopeptidase (NEP; EC 3.4.24.11; CD10) on nonstimulated cultured human keratinocytes obtained from healthy skin. Membrane expression of CD13 and CD10 was analysed by FACS and fluorescent microscope. Functional properties of CD13 and CD10 were examined by testing their enzymatic activity towards selective substrates. The data were compared to those obtained on cultured nonstimulated human skin fibroblasts expressing both CD13/APN and CD10/NEP. Approximately one-third (i.e. 31.7+/-2.8%; n=3) of cultured keratinocyte express CD13 as compared to fibroblasts which are 100% CD13(+) (n=3). Density of CD13 on keratinocytes is several times lower than on fibroblasts. Membrane CD13 expression on keratinocytes was associated with significant enzyme activity, which on the basis of substrate (L-Ala-betaNA) and inhibitor (bestatin, actinonin) selectivity could be ascribed to aminopeptidase N. Kinetic parameter V(max) revealed lower APN activity expressed on keratinocytes than on fibroblasts (V(max)=1.49+/-0.08 microM/60 min/5 x 10(4) cells for keratinocytes, n=3 versus V(max)=4.09+/-0.76 microM/60 min/5 x 10(4) cells for fibroblasts, n=3). Likewise, K(m) value of APN on keratinocytes was lower as compared to fibroblasts (K(m)=0.307+/-0.090 mM for keratinocytes, n=3 versus K(m)=0.766+/-0.065 mM for fibroblasts, n=3). CD13 demonstrated on cultured keratinocytes, is at least partly due to its constitutive expression since it was also found on freshly prepared epidermal skin cells. Inhibitors of APN, actinonin, bestatin and substance-P, as well as the APN blocking antibody WM-15, decreased keratinocytes growth. In contrast to membrane CD13 associated with APN enzyme activity, neither membrane CD10, nor its enzyme (NEP) activity could be found on the same keratinocyte samples. In conclusion, functional CD13, associated with APN activity, was found on about one third of cultured, non-stimulated keratinocytes, whereas no CD10/NEP was found on the same keratinocyte samples. Role of APN in regulation of keratinocyte growth is suggested, as its inhibition resulted in decreased keratinocyte growth.

A mannose-binding receptor is expressed on human keratinocytes and mediates killing of Candida albicans

Human keratinocytes are known to kill Candida albicans in vitro, but the mechanism of killing is not yet understood. Here, we demonstrate that spontaneous, ultraviolet-B-light-induced, alpha-melanocyte-stimulating-hormone-induced, and interleukin-8-induced Candida killing by keratinocytes can be inhibited with mannan and mannosylated bovine serum albumin (Man-BSA). A polyclonal goat serum raised against the human macrophage mannose receptor stained suprabasal keratinocytes, but no staining was observed on keratinocytes with a monoclonal antibody (mAb15) specific for the human macrophage mannose receptor. Mannose-affinity chromatography of keratinocyte extract isolated a 200 kDa protein, and on the Western blot the goat antiserum reacted with a 200 kDa protein. In radioligand binding studies, the binding of 125I-Man-BSA to human keratinocytes was inhibited by mannan in a concentration-dependent manner. Analysis of the binding revealed a single class keratinocyte mannose receptor with a KD of 1.4 x 10(-8) M and a Bmax of 1 x 10(4) binding sites per cell. The binding of 125I-Man- BSA to keratinocytes proved to be time-dependent, acid-precipitable, and Ca2+- and trypsin-sensitive. After trypsinization the receptors underwent a rapid recovery at 37 degrees C. These results demonstrate the presence of mannose receptor on human keratinocytes, and its active involvement in the killing of Candida albicans.

Exposure of human epidermal keratinocyte cell cultures to sulfur mustard promotes binding of complement C1q: implications for toxicity and medical countermeasures

Sulfur mustard (HD)-increased proteolytic activity, HD-enhanced expression of Fc receptor (FcR) on human epidermal keratinocytes (HEK) and associated inflammatory responses may contribute to HD pathology. Like the FcR, the first component of the classical complement (C') cascade, C1q, binds to the Fc region of antibody to mediate inflammatory responses. Complement C1q binds specifically to the C1q receptor (C1qR) on the blebs of apoptotic human keratinocytes and is proposed as a cell surface marker for apoptosis. Assays by fluorescent antibodies demonstrated significantly enhanced binding of C1q to HEK cell cultures exposed to HD. The cell populations of HEK that showed enhanced C1q binding also demonstrated an intermediate uptake of propidium iodide that was greater than in viable unexposed cells but less than in dead cells. The HD-enhanced C1q binding was concentration-dependent, negative by flow cytometry or weakly positive by digital scanning microscopy at 100 microM and positive by both methods at 300 microM. Binding of C1q was also time-dependent, weakly positive at 8 h, and positive at 16 and 24 h after HD exposure. The HD-increased C1qR that binds C1q to the surface of HEK might be a contributing mechanism or a marker for the inflammation and vesication associated with HD exposure.

Interleukin-11 therapy selectively downregulates type I cytokine proinflammatory pathways in psoriasis lesions

Psoriasis is a chronic inflammatory skin disease in which epidermal hyperplasia results from skin infiltration by type I T lymphocytes and release of associated cytokines. A multifunctional cytokine, rhIL-11, modulates macrophage and type I T-lymphocyte function in cell culture and shows anti-inflammatory activity in animal models. We are testing subcutaneous delivery of rhIL-11 to patients with psoriasis in a phase 1 open-label dose-escalation clinical trial. Tissue was obtained from lesional and uninvolved skin before and during treatment with rhIL-11 and was examined by histology/immunohistochemistry and quantitative RT-PCR. Expression of over 35 genes was examined in all patients, and multiple genetic markers of psoriasis were identified. Expression of numerous proinflammatory genes was elevated in psoriatic tissue compared with nonlesional skin. Seven of 12 patients responded well to rhIL-11 treatment. Amelioration of disease by rhIL-11, as shown by reduced keratinocyte proliferation and cutaneous inflammation, was associated with decreased expression of products of disease-related genes, including K16, iNOS, IFN-gamma, IL-8, IL-12, TNF-alpha, IL-1beta, and CD8, and with increased expression of endogenous IL-11. We believe that this is the first study in humans to indicate that type I cytokines can be selectively suppressed by an exogenous immune-modifying therapy. The study highlights the utility of pharmacogenomic monitoring to track patient responsiveness and to elucidate anti-inflammatory mechanisms.

Variational expression of functionally different macrophage markers (27E10, 25F9, RM3/1) in normal gingiva and inflammatory periodontal disease

Keratinocytes and macrophages share under immunologically activated conditions several surface proteins. We investigated immunohistochemically with monoclonal antibodies and the APAAP technique the expression pattern of 27E10 antigen (inflammatory macrophages), 25F9 antigen (resident macrophages) and RM3/1 antigen (intermediate macrophages in healing tissue) in 29 specimen biopsies of different stages of gingivitis and periodontitis. Macrophages of each subtype exhibited a different localization pattern depending on the stage of inflammation. Furthermore, suprabasal oral gingival epithelia showed a constant 27E10 expression, independent of the stage of inflammation. In contrast, all layers of the sulcus and pocket epithelia in gingivitis and periodontitis were strongly 27E10-positive, indicating immunological activation. 25F9 antigen was expressed on basal keratinocytes independent of the stage of inflammation, whereas RM3/1 was constantly negative on keratinocytes. The expression pattern of these functionally different macrophage markers on lesional macrophages and keratinocytes indicates varying differentiation and activation and suggests a participation of these cells in the local immune response in periodontal infection.

Effect of nickel on the activation state of normal human keratinocytes through interleukin 1 and intercellular adhesion molecule 1 expression

Patch tests with nickel on sensitive subjects induce a characteristic allergic reaction involving epidermal and dermal cells, as well as modulation of cytokines and adhesion molecule production. In order to gain further insight into the role of keratinocytes in this phenomenon, we assessed their activation state induced by Ni2+ by studying interleukin 1 (IL-1) production and intercellular adhesion molecule 1 (ICAM-1) expression, using normal human keratinocytes cultured in defined medium. In comparison with controls, the addition of subtoxic NiSO4 concentrations (0.1-20 micrograms/ml) to keratinocyte cultures induced a significant, but low release of IL-1 alpha and IL-1 beta at 24 and 48 h, detectable by enzyme-linked immunosorbent assay of the supernatants of treated cells. Moreover, IL-1 receptor antagonist was significantly increased in the supernatants and the cell extracts. Using fluorescence-activated cell sorter analysis, ICAM-1 expression at 24 h was found to be induced in a dose-dependent manner, reaching a level comparable with that obtained upon interferon-gamma (10 IU/ml) stimulation. Overall, these data confirm the existence of direct interactions between Ni2+ and keratinocytes, which generate immunological signals of major importance in the pathophysiology of allergic contact dermatitis.

Cytokine induction in human epidermal keratinocytes exposed to contact irritants and its relation to chemical-induced inflammation in mouse skin

In response to exogenous stimuli such as phorbol-12-myristate 13-acetate, ultraviolet B radiation, and lipopolysaccharide, human keratinocytes produce soluble mediators that are important in primary contact irritancy including cytokines that are associated with proinflammatory properties (interleukin-1 alpha [IL-1 alpha], tumor necrosis factor alpha), chemotaxis (IL-8), and growth activation (granulocyte/macrophage colony stimulating factor, IL-6, transforming growth factor alpha). We examined qualitative and quantitative changes in selected intracellular and secreted cytokines in human keratinocyte cultures in response to non-sensitizing contact irritants (croton oil, sodium lauryl sulfate, methyl salicylate, ethyl phenylpropiolate), sensitizing irritants (oxazolone, dinitrofluorobenzene), and ulcerative agents (phenol, benzalkonium chloride, chromium trioxide). The chemicals were also applied to mouse skin to assess whether the chemical-specific pattern of inflammation correlated with the in vitro production of keratinocyte-derived cytokines. Although all agents elicited neutrophils to the site of chemical application, time dependent and chemical-specific patterns of inflammation could be detected. Sodium lauryl sulfate, phenol, and croton oil induced increases in IL-8 production at non-cytotoxic concentrations in semi-confluent human keratinocyte cultures. Phenol and croton oil stimulated tumor necrosis factor alpha production, whereas croton oil was the only agent found to induce granulocyte/macrophage colony-stimulating factor production. Croton oil, phenol, benzalkonium chloride, and dinitrofluorobenzene induced the intracellular production of IL-1 alpha without a concomitant release into the medium. The release of cytokines occurred in parallel with a relative increase in cytokine-specific mRNA transcripts. Studies using neutralizing antibodies to tumor necrosis factor alpha and IL-1 alpha demonstrated that IL-8 induction by croton oil and phenol occurred directly rather than through autocrine circuits. These data suggest that a given pattern of cytokine production is chemical-specific and may predict the contribution of keratinocytes to skin inflammation.

Interleukin-4 and interferon-gamma interactions in the induction of intercellular adhesion molecule-1 and major histocompatibility complex class II antigen expression of normal human keratinocytes

Interleukin-4 (IL-4) that may be produced by T-helper cells in atopic lesions has immunomodulatory activities on skin cells which are poorly known. Our study was aimed at determining whether the cytokine exerts some effects on keratinocyte activation and can either enhance or antagonize interferon-gamma (IFN-gamma)-induced ICAM-1 or HLA-DR antigen expression. Using normal keratinocytes cultured in defined medium and cytofluorography, we showed that treatments of the human cells with the cytokine IL-4 alone had no effect on the induction of ICAM-1 or HLA-DR molecules. However, a transient, but significant enhanced expression of ICAM-1 was observed by the combination of IFN-gamma and IL-4 after 24 h of stimulation, which was followed by a reduction at 48 and 72 h. Conversely, IL-4, when added during the IFN-gamma activation stage, had no effect on MHC class II antigen expression of keratinocytes; however, the cytokine reduced the expression of these antigens when added 24 h before the stimulation by IFN-gamma. These results suggest that IFN-gamma and IL-4 may interact to regulate ICAM-1 and HLA-DR expression on keratinocytes.

Glycosylphosphatidylinositol (GPI)-anchored membrane proteins are constitutively down-regulated in psoriatic skin

Hyperproliferation of keratinocytes (KCs) in psoriasis has been found to be associated with excessive activation of a phospholipase C (PLC)/protein kinase C (PKC) signal transduction system. The molecular species of PLCs which are activated in psoriasis have not been thoroughly investigated. It was envisaged that if glycosylphosphatidylinositol (GPI)-specific PLC was activated in the membrane of psoriatic epidermal cells, it would render these cells devoid of those proteins which are anchored to the cell membrane through their GPI moiety. In order to test this possibility, four GPI proteins (CD16, CD55, CD58, and CD59) were determined immunohistochemically in normal and psoriatic skin. In normal skin, CD55 and CD59 were strongly expressed on epithelium and vascular structures, whereas CD16 and CD58 were strongly expressed only on epithelium. The expression of all four GPI proteins was decreased in non-lesional psoriatic skin and virtually abolished in lesional psoriatic skin. A control transmembrane protein, CD46, was strongly expressed in normal and non-lesional psoriatic skin, and its expression was not significantly decreased in psoriatic lesions. The absence or reduction of GPI proteins was not seen in the lesions of several other inflammatory and proliferative diseases studied.

Cytokine system as potential target for antipsoriatic therapy

Cytokines are produced by a variety of cells and have numerous of overlapping activities. There is increasing evidence that cytokines play a crucial role in the pathogenesis of psoriasis and of other dermatologic diseases. This review summarizes current knowledge as to how the altered cytokine network is involved in the accumulation of inflammatory cells in lesional skin, and how the cytokines are involved in epidermal hyperproliferation. The actions of the most important therapeutic compounds, such as corticosteroids, dithranol, cyclosporine, retinoids, vitamin D3 analogues and ultraviolet radiation, on the cytokine system are also discussed. Consideration is given as to how the effects on the production of cytokines and/or cytokine receptors contribute to their therapeutic action.

Cellular adhesion antigen modulation in purpura pigmentosa chronica

BACKGROUND

Purpura pigmentosa chronica is an inflammatory skin disorder probably caused by an allergic reaction. Delayed-type hypersensitivity or immunocomplex vasculitis has been considered as a possible mechanism.

OBJECTIVE

Detailed analysis of cell adhesion molecule (CAM) modulation may give further insights into the pathogenesis and underlying immune reaction of this disease.

METHODS

By immunohistochemical techniques we investigated the in situ expression of integrins, selectins, and CAMs of the immunoglobulin superfamily.

RESULTS

Infiltrating lymphocytes expressed LFA-1, LFA-2, VLA-4, and VLA-5, whereas some of the macrophages were also positive for p150/95 and MAC-1. VLA-1 was found on lymphocytes near the basement membrane of the epidermis. Compared with uninvolved or healthy skin endothelial cells showed upregulation of ICAM-1, VCAM-1, and, focally, E-selectin. Some fibroblasts were positive for ICAM-1. ICAM-1 was also upregulated on lesional keratinocytes that also expressed alpha 2, alpha 3, and alpha 6 integrin chains on basal and suprabasal epidermal layers.

CONCLUSION

Our findings demonstrate characteristic modifications in the expression of CAMs in purpura pigmentosa chronica and indicate the involvement of the epidermis in this disease. This modulation shows close parallels to those described for chronic delayed-type immune reactions of the skin.

Adhesion molecule expression in chronic inflammatory periodontal disease tissue

Differences in lymphocyte populations have been demonstrated in gingivitis and periodontitis lesions. A differential expression of adhesion molecules may play a role in lymphocyte trafficking in these tissues. An indirect avidin biotin immunoperoxidase technique was used to stain a range of adhesion molecules in tissue sections of 21 gingival biopsies from both gingivitis and periodontitis subjects. These specimens were placed into three groups according to the size of the infiltrate. ICAM-1, PECAM-1 and LECAM-1 expression on mononuclear cells in the inflammatory infiltrates increased significantly with increasing size of infiltrate. Approximately 50% of these mononuclear cells were LFA-1+ and CD29+. When specimens were grouped according to their putative disease status there were no significant differences between mononuclear cell adhesion molecule expression in small infiltrates from either gingivitis or adult periodontitis subjects. This was also the case with larger lesions from both clinical groups. Therefore there does not appear to be a differential expression of adhesion molecules on lymphocytes in gingivitis and periodontitis tissue. Endothelial cells were positive for ICAM-1, PECAM-1, CD29, GMP-140 but negative for ELAM-1. Keratinocyte expression of ICAM-1 increased with increasing size of infiltrate although in heavy infiltrates, cells in the region of the junctional epithelium which were positive in small lesions, became ICAM-1 negative. The upper layers of the oral epithelium were positive for LECAM-1 in small infiltrates and with increasing size of infiltrate, the lower layers and many of the sulcular and junctional epithelium keratinocytes were positive.(ABSTRACT TRUNCATED AT 250 WORDS)

Macrophage markers 25F9 and 27E10 on human keratinocytes in normal and diseased skin

In the present study, an immunohistochemical analysis was made of the expression pattern of different macrophage markers such as 25F9, 27E10 and RM 3/1 on the surface of human keratinocytes (HK) in biopsies obtained from healthy volunteers and from patients with lichen planus, chronic cutaneous graft-versus-host reaction, mycosis fungoides, and purpura pigmentosa chronica. In biopsies from the healthy volunteers and from both clinically involved and uninvolved skin of the patients, the HK of the basal cell layer exhibited a specific peroxidase-positive reaction when the monoclonal antibody against 25F9 was used. Lesional HK from all patients studied displayed 25F9 and 27E10 in nearly the entire epidermis. The present findings provide further evidence that HK and macrophages share a number of common cell surface moieties.