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Biomedical subjects

T A Luger

Publications and source records attributed to T A Luger.

At least 163 records · Page 9Linked to original sources
PubMed1994

In vivo effects of interleukin-10 on contact hypersensitivity and delayed-type hypersensitivity reactions.

Interleukin (IL) 10 is a recently discovered cytokine, originally isolated from T-helper 2 (Th2) cells, which inhibits cytokine production of T-helper 1 (Th1) cells. Because Th1 cells appear to be of importance during the contact hypersensitivity reaction (CHS) we hypothesized that IL-10 might modulate the outcome of CHS in vivo. Intraperitoneal injection of murine recombinant IL-10 (1000 ng) into naive mice 24, 72, or 120 h before sensitization by epicutaneous application of 2,4-dinitrofluorobenzene (DNFB) did not affect ear swelling when ears were challenged 5 d later. However, intraperitoneal injection of IL-10 into already sensitized mice 24 h before challenge resulted in a significant suppression of the ear swelling response, suggesting that under the conditions employed IL-10 is able to block the effector phase, but not the induction phase of CHS in vivo. The suppression could be reversed by the concurrent injection of an IL-10 antibody. Moreover, heat inactivation of native IL-10 resulted in loss of the inhibitory capacity. When mice were sensitized by subcutaneous injection of trinitrophenyl-coupled spleen cells (DTH) instead of epicutaneous application of the hapten (CHS), intraperitoneally-injected IL-10 suppressed the effector phase, but also the induction phase of DTH. IL-10 did not inhibit the toxic ear-swelling response induced by topical application of two irritants tested (croton oil or benzalkonium chloride). The capacity of IL-10 to suppress the effector phase of CHS and DTH supports an important role for this cytokine in the downregulation of type IV immune reactions in vivo. The finding that IL-10 suppresses the induction of DTH, but not of CHS, further suggests that CHS and DTH are related but distinct immune reactions.

Animals↗
PubMed1994

Regulation of monocyte and keratinocyte interleukin 6 production by transforming growth factor beta.

There is strong evidence for a complex network-like interaction between cytokines, growth factors and other mediators being responsible for cell growth and differentiation as well as for the outcome of an inflammatory reaction. Therefore, the regulation of the production of the ubiquitous proinflammatory cytokine interleukin 6 (IL-6) by transforming growth factor beta (TGF beta) was investigated. Human peripheral blood mononuclear cells (PBMC), human normal keratinocytes (HNK), and an epidermoid carcinoma cell line (KB) were treated with TGF beta 1 or TGF beta 2 and subsequently IL-6 secretion was evaluated. Addition of TGF beta 1 as well as TGF beta 2 to PBMC, HNK and KB cells resulted in a significantly increased release of IL-6 activity. The inducing effect of TGF beta was does dependent and maximal when supernatants were harvested 48 h after stimulation. In addition, upon Western blot analysis using a monoclonal IL-6 antibody significantly increased amounts of IL-6 protein were detected in KB cell supernatants following stimulation with TGF beta 1. These results were further confirmed at the transcriptional level using a cDNA probe specific for IL-6 and Northern blot analysis. Accordingly, an increased IL-6 mRNA expression in PBMC or KB cells was detected following TGF beta 1 treatment. These findings indicate that TGF beta in contrast to its antiinflammatory capacities also may stimulate IL-6 production in PBMC and keratinocytes. This further supports the possibly important immunoregulatory role of growth factors such as TGF beta.

Blotting, Northern↗
PubMed1994

Cytokine release by peripheral blood mononuclear cells is affected by 8-methoxypsoralen plus UV-A.

Psoralen plus UV-A (PUVA) is an effective therapy for psoriasis but also for other inflammatory dermatoses. The precise mechanisms of action, however, are not absolutely clear. Therefore, the effect of PUVA on the release of the proinflammatory cytokines interleukin (IL)-1, IL-6, IL-8 and tumor necrosis factor alpha (TNF alpha) was studied. Peripheral blood mononuclear cells (PBMC) obtained from humans were incubated with 8-methoxypsoralen (8-MOP) and exposed to UV-A (20 kJ/m2). This treatment resulted in a significant reduction of IL-6 and IL-8 amounts in the supernatants. In addition, an inhibition of IL-1 beta and TNF alpha production by lipopolysaccharide (LPS)-stimulated PBMC was observed upon PUVA treatment. Accordingly, northern blot analysis showed decreased levels of mRNA encoding for IL-1 beta, IL-6, IL-8 and TNF alpha in PUVA-treated PBMC. Finally PBMC were obtained from psoriatics undergoing oral photochemotherapy before the beginning and after completion of treatment. The PBMC collected after PUVA spontaneously produced significantly less IL-6 and IL-8 in comparison to the respective samples obtained before therapy. A similar suppression of IL-1 beta and TNF alpha by in vivo PUVA was found in LPS-stimulated PBMC. The present data demonstrate that PUVA both in vitro and in vivo suppresses the production of the proinflammatory cytokines IL-1 beta, IL-6, IL-8 and TNF alpha by PBMC. Because these cytokines are important in the mediation of inflammatory reactions, one may speculate that the inhibitory effects could contribute to the antiinflammatory activity of PUVA.

Cytokines↗
PubMed1994

Proopiomelanocortin-derived peptides are synthesized and released by human keratinocytes.

Proopiomelanocortin (POMC), the precursor for melanotropic, corticotropic, and opioid peptides such as alpha-melanocyte-stimulating hormone (alpha MSH), ACTH, and other related peptides, was originally identified as a product of the pituitary gland. However, recent evidence shows that POMC products can also be produced by nonpituitary tissues. Because keratinocytes, the major constituent of the epidermis exhibit the capacity to release a variety of proinflammatory and immunomodulatory mediators, the present study was performed to investigate whether human keratinocytes are able to produce POMC-derived peptides. Supernatants of human normal keratinocytes and an epidermal carcinoma cell line (A431) contained significant levels of immunoreactive alpha MSH and ACTH. Upon immuneprecipitation and size-exclusion chromatography, keratinocyte-derived alpha MSH exhibited a molecular mass of approximately 1 kD and was biologically active as demonstrated in a tyrosinase bioassay. Northern blot analysis revealed the expression of POMC-specific transcripts (1.3 kb) in both normal keratinocytes and A431 cells. The production of alpha MSH and ACTH could be significantly upregulated both at the protein and mRNA level upon treatment with phorbol myristate acetate, ultraviolet light, or interleukin 1. These data provide first evidence that human keratinocytes produce POMC-derived peptides such as alpha MSH and ACTH. Because POMC-derived peptides recently have been recognized as potent immunomodulatory mediators, their presence in the epidermis may have a major impact on the skin immune system.

Adrenocorticotropic Hormone↗
PubMed1994

Pentoxifylline in vivo down-regulates the release of IL-1 beta, IL-6, IL-8 and tumour necrosis factor-alpha by human peripheral blood mononuclear cells.

Pentoxifylline (PTX) is a methylxanthine compound known to inhibit the production of tumour necrosis factor-alpha (TNF-alpha), which is an important inflammatory mediator. There is also recent evidence that PTX may influence other inflammatory cytokines, such as interleukin-1 (IL-1) and IL-6. Due to the therapeutic implications, the present study addressed the in vivo effects of PTX on the release of TNF-alpha, IL-1 beta, IL-6 and IL-8 by human peripheral blood mononuclear cells (PBMC). When PBMC were obtained from healthy volunteers ingesting 5 x 400 mg PTX orally for 2 days, the ability of PBMC cultured for 24 hr to release TNF-alpha was significantly reduced, while secretion of IL-1 beta, IL-6 and IL-8 was not affected. However, when PBMC were obtained from the same individuals 5 days after PTX had been stopped, the release of all four cytokines was significantly suppressed. This effect appeared to be exerted at the transcriptional level, since Northern blot analysis revealed reduced cytokine transcripts. In order to gain more insight into the effect of PTX on cytokine release, PBMC were obtained from normal volunteers, either stimulated with lipopolysaccharide (LPS) or left unstimulated, and subsequently incubated in vitro with PTX for 48 hr. Under these conditions, only TNF-alpha was found to be reduced by PTX, while IL-1 beta and IL-8 were not affected, IL-6 was even enhanced. However, when PBMC were incubated with PTX for 24 hr, PTX removed thereafter by medium change and cells further cultured, the production not only of TNF-alpha but also of IL-1 beta, IL-6 and IL-8 was reduced, demonstrating that PTX exerts diverse (inhibitory) effects on cytokine release by PBMC.

Blotting, Northern↗
PubMed1993

Human monocytes and keratinocytes in culture ingest hydroxyethylstarch.

Severe itching for unknown reasons has been reported after administration of hydroxyethylstarch (HES) in haemodilution therapy of humans. In skin sections from patients who had received HES for otological reasons HES deposition was found by immunohistochemical methods in keratinocytes, epidermal dendritic cells, endothelial cells and macrophages. The aim of the present investigation was to study the interaction of cultured human monocytes and keratinocytes, normal (HNK) and malignant (KB, A431), with FITC-conjugated HES (200/0.5). Peripheral blood monocytes from healthy donors were isolated by Ficoll-Hypaque gradient centrifugation and adherence to plastic surfaces. Cells were incubated with HES-FITC (1 mg/ml) for 10, 20, 30, 60 and 120 min at 37 degrees C, washed several times to minimize cell-associated HES-FITC. The uptake of HES-FITC (200/0.5) was detected by fluorescence microscopy and flow cytometry. Monocytes and keratinocytes (HNK, KB, A431) acquired significant amounts of HES-FITC after 120 min. Endocytosis was blunted by the addition of unconjugated HES in ten-fold concentration. At 4 degrees C, a further inhibition was achieved, indicating an uptake of HES-FITC by monocytes and keratinocytes in vitro. These results indicate that a connection between the storage of HES by keratinocytes and monocytes and the observed itching in patients might be possible.

Cells, Cultured↗
PubMed1993

Human keratinocytes in vivo and in vitro constitutively express the 72-kD heat shock protein.

Exposure of cells to elevated temperatures induces a physiologic response characterized by the synthesis of a specific set of proteins (heat shock or stress proteins, HSPs) mediating repair mechanisms and protection from cellular damage. In the present study upon immunohistochemistry using a specific monoclonal antibody, the constitutive and heat-induced expression of the 72-kD HSP (HSP72) in normal human skin and in human epidermal cell lines (KB, A431) was investigated. Normal (unstressed) epidermis and adnexal structures of normal human skin were found to constitutively express HSP72. In contrast, a substantial HSP72 expression could not be observed in the dermal cellular compartment. In vitro heat treatment of punch biopsies from normal skin (42 degrees C, 4 h) resulted in a further increase of epidermal HSP72 expression. In addition, dermal cells were found to be induced to express HSP72. To further evaluate the spontaneous HSP72 expression of epidermal cells two epidermoid carcinoma cell lines (A431, KB) were investigated. Upon immunohistochemistry and Western blot analysis a significant HSP72 expression could be detected in unstressed KB and A431 cells. In contrast, a human fibrosarcoma cell line (HT1080) was negative for HSP72 at 37 degrees C but upon heat treatment a strong induction was observed. Furthermore, Northern blot analysis using a cDNA probe specific for human HSP72 revealed a constitutive expression of HSP72 mRNA in both epidermal cell lines. These findings demonstrate a significant expression of the stress-inducible HSP72 in unstressed human skin as well as in epidermal cell lines, suggesting that HSP72 may inherently be involved in the protective function of normal human skin.

Blotting, Northern↗
PubMed1993

Pentoxifylline suppresses irritant and contact hypersensitivity reactions.

Pharmacologic suppression of the effector phase of contact hypersensitivity appears to have major relevance with regard to treatment of type IV reactions like contact dermatitis. Recently, tumor necrosis factor alpha has been shown to be a critical mediator in hapten-induced irritant and contact hypersensitivity reactions, thus offering new possibilities, for therapeutic intervention. Pentoxifylline, a methylxanthine derivative used in the treatment of vascular disorders, currently has been found to suppress the production of tumor necrosis factor alpha by human and murine leukocytes. Therefore, the effect of pentoxifylline on the elicitation phase of contact hypersensitivity was studied. Intraperitoneal injection of pentoxifylline into sensitized Balb/c and C3H/HeN mice before application of the challenging hapten dose resulted in a significant reduction of the outcome of the contact hypersensitivity reaction. The suppressive effect of pentoxifylline was dose dependent and maximally pronounced upon injection 3 h before hapten application. In contrast to the effector phase of contact hypersensitivity, induction of contact hypersensitivity was not affected by pentoxifylline when injected into naive mice before performance of sensitization. In addition, irritant dermatitis induced by 1% croton oil or 5% benzalkonium chloride was suppressed by pentoxifylline as well. These data suggest a potential pharmacologic intervention, with pentoxifylline as a means to treat contact dermatitis.

Administration, Topical↗
PubMed1993

The 55-kD tumor necrosis factor receptor on human keratinocytes is regulated by tumor necrosis factor-alpha and by ultraviolet B radiation.

In previous studies we showed that cultured human keratinocytes expressed the 55-kD TNF receptor (TNFR) and that its expression the important for TNF alpha-mediated upregulation of intercellular adhesion molecule-1 (ICAM-1) expression on keratinocytes. Because factors that either reduce or enhance TNFR expression are likely to have a major impact on the biological effects of TNF alpha on keratinocytes, these studies were conducted to determine the factors that regulate its expression on keratinocytes. Using reverse transcriptase polymerase chain reaction, human keratinocytes were shown to lack 75-kD TNFR expression, indicating that TNF responsiveness of human keratinocytes critically depended on regulation of 55-kD TNFR expression. Human keratinocyte 55-kD TNFR surface and mRNA expression was found to be regulated in vitro by recombinant human (rh) TNF alpha. Stimulation of keratinocytes with rhTNF alpha initially decreased, but later increased, 55-kD TNFR surface expression. This biphasic modulation of 55-kD TNFR surface expression was associated with concomitant changes in 55-kD TNFR mRNA expression. Ultraviolet B (UVB) radiation, a well-known inducer of synthesis and secretion of TNF alpha by human keratinocytes, was found to mimic TNF alpha-induced modulation of 55-kD TNFR surface and mRNA expression via a TNF alpha-mediated autocrine regulatory mechanism. Production of soluble 55-kD TNFR by human keratinocytes remained unaffected by TNF alpha stimulation or UVB irradiation. These studies provide clear evidence that membrane expression of the human 55-kD TNFR may be regulated in human keratinocytes by the ligand itself: TNF alpha. Since in previous studies UVB irradiation transiently inhibited TNF alpha-induced human keratinocyte ICAM-1 expression, it is proposed that UVB radiation-induced biphasic modulation of human keratinocyte 55-kD TNFR expression may affect the capacity of these cells to respond to TNF alpha.

Base Sequence↗
PubMed1993

[Dyshidrosiform bullous pemphigoid].

Dyshydrosiform bullous pemphigoid is a clinical variant of bullous pemphigoid in which the lesions appear primarily on palms and soles. Knowledge of this unusual manifestation of bullous pemphigoid may be of practical relevance, since it has to be included in the differential diagnosis of blistering palmoplantar dermatoses. The correct diagnosis is confirmed by histological examination and immunofluorescence, which reveal all the characteristic hallmarks of bullous pemphigoid. Three patients with dyshydrosiform bullous pemphigoid are presented; clinical and histological aspects, findings on immunofluorescence, differential diagnosis and therapy are discussed.

Aged↗
PubMed1993

[Pemphigus herpetiformis].

Pemphigus herpetiformis is an unusual variant of pemphigus. Clinically it can resemble Duhring's disease, while histopathological examination and, in particular immunofluorescence yield findings diagnostic for pemphigus. As pemphigus herpetiformis responds quite well to sulfones, recognition of this rare disorder is of practical relevance. In the present report, a case of pemphigus herpetiformis with an unusually young age of onset is presented. In addition, clinical features, results of histopathological examination and immunofluorescence, differential diagnosis and treatment are discussed.

Adult↗
PubMed1992

Autocrine growth limitation of human papillomavirus type 16-harboring keratinocytes by constitutively released tumor necrosis factor-alpha.

TNF-alpha is known to exert antitumor and antiviral effects and to participate in the regulation of the immune response. In our study we demonstrate that human rTNF-alpha specifically blocks growth of SK-v keratinocyte cell line harboring and expressing human papillomavirus type 16 (HPV16) sequences. This inhibitory effect was shown by [3H]TdR incorporation and cell counting. Binding experiments with 125I-TNF-alpha showed that SK-v cells express about 10,000 single class TNF-alpha R per cell with affinity constant of about 0.7 nM. Binding of 125I-TNF-alpha could be inhibited by htr-9 mAb recognizing a 55/60-kDa type I TNF-alpha R but not by utr-1 mAb recognizing 75/80-kDa type II TNF-alpha R or irrelevant mAb specific for HPV16E7 protein. Addition of anti-TNF-alpha antibodies to SK-v cell culture resulted in significant (p < 0.05), dose-dependent stimulation of their proliferation. SK-v cells constitutively expressed TNF-alpha mRNA, and SK-v CM contained TNF-alpha, as demonstrated by Northern blot analysis, a specific ELISA, Western blot analysis, and a bioassay with TNF-alpha-sensitive L-M cells. HPLC gel filtration of SK-v cell CM showed that the factor cytotoxic for L-M cells coeluted with immunoreactive TNF-alpha. These results demonstrate that HPV16-harboring SK-v cells constitutively express and release immunoreactive and biologically active TNF-alpha that in turn may exert an autocrine growth inhibitory effect. This phenomenon could represent one of the self-limiting mechanisms controling growth of HPV-induced neoplasia.

Cell Division↗
PubMed1992

Production of natural killer cell activity-augmenting factor (interleukin-6) by human epiphyseal chondrocytes.

OBJECTIVE: We sought to determine the capacity of human epiphyseal chondrocytes to modulate the cytotoxic activity of human natural killer (NK) cells by determining whether they release interleukin-6 (IL-6), a cytokine recently shown to stimulate NK cell activity. METHODS: Conditioned medium from human epiphyseal chondrocyte cultures (Ch-CM) was tested for IL-6 activity using the B9 cell hybridoma assay. Its NK cell-stimulating capacity in the presence of K562 (myelogenous leukemia) cells or human chondrocytes was evaluated in a 4-hour 51Cr-release assay. Ch-CM-derived IL-6/NK cell-augmenting factor activity was partially purified by high-performance liquid chromatography (HPLC) gel filtration and Western blot. RESULTS: Ch-CM contained an NK cell-augmenting factor (NKAF) which was blocked by IL-2 or IL-6 antibodies. Ch-CM did not contain detectable IL-2 activity, but it stimulated IL-2 production by human peripheral blood lymphocytes (PBL). This IL-2-inducing capacity was inhibited by IL-6 antibodies, indicating that chondrocytes release an IL-6-like activity. Ch-CM significantly enhanced the proliferation of IL-6-dependent B9 hybridoma cells, and Western blot analysis of Ch-CM revealed specific bands corresponding to those of highly purified IL-6. Upon HPLC gel filtration, chondrocyte NKAF copurified with chondrocyte IL-6. Pure IL-6 and chondrocyte IL-6 were tested for their ability to stimulate the cytotoxic activity of human PBL against chondrocytes. Both mediators significantly enhanced chondrocyte killing. Lysis of chondrocytes by PBL was mediated by NK cells, since depletion of CD16+ cells resulted in inhibition of the activity. CONCLUSION: Thus, upon stimulation, chondrocytes produce IL-6 which, through IL-2 induction, augments the activity of NK cells against K562 target cells as well as against chondrocytes.

Blotting, Western↗
PubMed1992

Circulating serum levels of interleukin 6 and C-reactive protein after liver transplantation.

The study objectives were to investigate serum levels of interleukin-6 and C-reactive protein (CRP) after liver transplantation to correlated measurements with various clinical parameters. Twenty-three patients were studied after orthotopic liver transplantation. Serum IL-6 activity was evaluated by testing its capacity to induce proliferation of the IL-6-dependent hybridoma cell line B9. CRP was assessed by a nephelometric method. Only two of seven patients with acute cellular rejection developed an increase of serum IL-6 and CRP. In contrast to this rejection group, elevated IL-6 levels were observed in 7/9 patients with bacterial infections. Peak values for IL-6 were observed one day and for CRP two days after clinical diagnosis of infection. CMV disease was also associated with markedly increased IL-6 and CRP levels in 5/7 patients. Surprisingly, levels in this condition were approximately in the same range as in bacterial infection. IL-6 and CRP serum levels seen in bacterial infection and CMV disease were significantly higher than those in rejection (P less than 0.001). Serum IL-6 activity was neutralized by an antiserum directed against recombinant human IL-6. Preferential elevations of IL-6 and CRP represent one feature of bacterial and viral infections. Elevation of TNF during rejection as described earlier is only rarely accompanied by increased serum IL-6 levels.

Bacterial Infections↗
PubMed1992

Ultraviolet radiation effects on human keratinocyte ICAM-1 expression: UV-induced inhibition of cytokine-induced ICAM-1 mRNA expression is transient, differentially restored for IFN gamma versus TNF alpha, and followed by ICAM-1 induction via a TNF alpha-like pathway.

Human keratinocytes (KC) during the course of inflammatory dermatoses strongly express the surface molecule ICAM-1, which plays an important role in the generation of the epidermal inflammatory infiltrate by mediating leukocyte-keratinocyte interactions. Accordingly, KC ICAM-1 expression is known to be induced in vivo and in vitro by cytokines either via the TNF alpha/TNF beta or via the IFN gamma-mediated pathway. In contrast, ultraviolet (UV) radiation previously has been found to potently inhibit cytokine-induced KC ICAM-1 surface expression by a sublethal mechanism. In order to further define this novel immunosuppressive effect of UV light, the effects of in vitro UV radiation on ICAM-1 mRNA expression in transformed human KC (KB cells) were examined. Accordingly, UV light (0-100 J/m2) inhibited IFN gamma- as well as TNF alpha-induced ICAM-1 mRNA expression, if KC were cytokine stimulated immediately after irradiation. After a 12-h incubation period, however, IFN gamma responsiveness was found to be restored in irradiated cells, whereas restoration of responsiveness to TNF alpha required at least a 24-h recovery phase. Moreover, UV light alone did not alter ICAM-1 mRNA levels after 4, 12, or 24 h. After 48 h, however, a significant increase in ICAM-1 mRNA and surface expression in UV-irradiated KC could be observed. In addition, this increase could be superinduced by stimulation of irradiated KC with IFN gamma, but not with TNF alpha. UV-induced upregulation of ICAM-1 expression could be mimicked by stimulating unirradiated cells with supernatants derived from UV-irradiated cells. Addition of biologically active anti-TNF alpha antibodies to UV-irradiated cells or to supernatants derived from UV-irradiated KC, however, did not even partially abolish this ICAM-1-inducing activity. UV light thus seems to affect KC ICAM-1 mRNA expression in a biphasic manner: an early period of inhibition of cytokine-induced ICAM-1 expression is transient and followed by restoration of responsiveness to ICAM-1-inducing cytokines. Moreover, UV itself is able to induce ICAM-1 mRNA expression at this later time point via a TNF alpha-like pathway. These studies identify UV irradiation as a potent modulator of cytokine regulated ICAM-1 gene transcription with the capacity to induce both inhibitory as well as enhancing effects.

Blotting, Northern↗