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J Knop

Publications and source records attributed to J Knop.

At least 127 records · Page 7Linked to original sources
PubMed1994

Enhanced expression of IL-8 in normal human keratinocytes and human keratinocyte cell line HaCaT in vitro after stimulation with contact sensitizers, tolerogens and irritants.

To investigate the interleukin-8 production of keratinocytes after stimulation in vitro we have used various agents: (i) contact sensitizer (2,4-dinitrofluorobenzene, 3-n-pentadecylcatechol); (ii) tolerogen (5-methyl-3-n-pentadecylcatechol); (iii) irritant (sodium lauryl sulfate). Interleukin-8 gene expression was assessed by northern blot hybridization of the total cytoplasmic RNA extracted from subconfluent normal human keratinocyte cultures and the keratinocyte cell line HaCaT using a radiolabeled DNA probe specific for human interleukin-8. Interleukin-8 gene expression was markedly increased upon in vitro stimulation after 1-6 h with contact sensitizers, tolerogen and the irritant. In contrast, interleukin-8 production was not detectable in unstimulated normal human keratinocytes or the HaCaT keratinocyte cell line. These results suggest that the induction and production of interleukin-8 is a response to nonspecific stimuli and may play a critical role in the early response to immunogenic or inflammatory signals in man.

Catechols↗
PubMed1994

Identification and induction of human keratinocyte-derived IL-12.

Interleukin 12 is a heterodimeric molecule that serves as a potent co-stimulator enhancing the development of Th1 cells. As one of the classical Th1 cell-mediated responses is contact sensitivity in skin, we wondered whether IL-12 might be produced by epidermal cells and serve as a mediator of this immune response. Using a sensitive, quantitative PCR technique we demonstrate that p35 chain mRNA of IL-12 is produced constitutively by human epidermal cells, whereas p40 chain mRNA can only be detected in epidermis treated with contact allergen, but not epidermis exposed to irritants or tolerogens. Time course studies showed a dramatic induction of IL-12 p40 mRNA 4 h after in vivo allergen treatment reaching peak strength after 6 h. In cell depletion assays we show that epidermal keratinocytes are the major source of this cytokine in the epidermis. This was further supported by analysis of mRNA derived from the human keratinocyte cell line HaCat expressing IL-12 p35 and p40 mRNA upon stimulation. The presence of bioactive IL-12 in supernatants derived from allergen-stimulated epidermal cells was demonstrated by IL-12-specific bioassay. Additional evidence for the functional importance of IL-12 in primary immune reactions in skin was obtained in allogeneic proliferation assays using human haptenated epidermal cells containing Langerhans cells as APC and allogeneic CD4+ T cells as responders. Anti-IL-12 mAb inhibited the proliferation of T cells by approximately 50%. In aggregate our data demonstrate that nonlymphoid keratinocytes are capable of producing functional IL-12 and provide evidence for the functional significance of IL-12 in primary immune responses in skin.

Antibodies, Monoclonal↗
PubMed1993

[Use of psychiatric emergency clinics in Copenhagen and Frederiksberg by schizophrenic patients].

All patients contacts at the four psychiatric emergency rooms in Copenhagen and Frederiksberg were registered every tenth day during 1985 (a total of 1969 patient contacts). Based on this material, we have compared patients who were given the diagnosis schizophrenia with other patients attending the psychiatric emergency rooms as regards demographic data, attendance patterns and treatment. There were 387 contacts from schizophrenic patients, of which 69.8% were men and 30.2% women. The schizophrenic patients were significantly younger than the other patients, and significantly more of them were unmarried, living alone and on pensions. A quarter of the schizophrenic patient contacts ended in hospital admission, either directly or after spending the night in the emergency room, 10% spent the night only, and 65% left the emergency room the same day with or without further appointments. There were signs that many of the schizophrenic patients, especially the men, used the emergency rooms as a means of human contact and a "shelter", compensating for the lack of a more personal social network. This is seen in connection with the fact that the male patients were to a greater degree without a family network. On the other hand, significantly more female schizophrenic patients were admitted to hospital or were offered overnight stays in the emergency room. Schizophrenic patients are regarded as large-scale users of psychiatric emergency rooms, which is seen in relation to recent years' limited capacity for hospital admission and lack of relevant options for housing, treatment and rehabilitation. The plans for community psychiatry in Copenhagen are expected to consider the special problems which these patients face.

Adult↗
PubMed1993

Functional and morphological characterization of 4F7+ spleen accessory dendritic cells.

Recently we have reported on the production of the mAb 4F7. This recognizes a molecule that is upregulated on dermal and epidermal dendritic cells after application of contact allergen. Furthermore, this antibody detects an antigen on spleen and lymph node dendritic cells. In this study, we characterize 4F7+ spleen dendritic cells and show that the mAb recognizes in situ few labeled cells in the white pulp of the spleen and approximately 1% of spleen single cell suspensions as evidenced by cell enrichment, immunoperoxidase staining and FACS analysis. Immunohistological characterization of the cells with mAbs revealed the expression of class II, class I MHC antigens, 33D1, CD11c, ICAM-1, and CD45 molecules. After enrichment and cultivation for approximately 3 days, these cells showed no adherent properties. The capacity of 4F7+ spleen dendritic cells to activate allogeneic T cells in the primary mixed lymphocyte reaction was similar to freshly isolated Ia+ Langerhans cells. With regard to the induction of a proliferative response of CD4+ naive T cells that were incubated with concanavalin A or anti-CD3 mAb, 4F7+ spleen dendritic cells were two to three times more potent than spleen microphages and B cells. Furthermore, 4F7+ cells efficiently stimulated the antigen dependent proliferation of a T helper cell line. The mAb 4F7 will be useful for the purification of dendritic cells and for functional and molecular biological studies.

Animals↗
PubMed1993

Expression of an epitope as detected by the novel monoclonal antibody 4F7 on dermal and epidermal dendritic cells. I. Identification and characterization of the 4F7+ dendritic cell in situ.

Ears of Balb/c mice were treated epicutaneously with 0.5% 2,4-dinitrofluorobenzene (DNFB) to obtain monoclonal antibodies characterizing molecules on epidermal dendritic cells that are involved in the induction and elicitation of allergic contact dermatitis. Six hours after this treatment, epidermal cells were prepared from the ear skin, and Ia-positive cells were enriched by indirect panning and injected into rats. Hybridomas were generated and supernatants were screened for antibodies on ear skin from DNFB-treated and untreated animals. A clone (4F7) was isolated and characterized by immunohistochemistry and immunoelectron microscopy on murine skin and other organs. The monoclonal antibody 4F7 (IgG1) recognized distinct dendritic cells in the dermis and very few dendritic cells in the paracortical area of the lymph nodes, the white pulp of the spleen, and the mucosa of the large intestine in normal animals. By fluorescence activated cell sorter analysis, it stained about 1.64% of the dermal and no epidermal cells in the skin of untreated animals. Approximately 50% of the dermal 4F7+ cells expressed Ia molecules on their surface. Six hours after application of 0.5% DNFB, the expression of the 4F7 antigen was strongly enhanced in vivo on dendritic cells in both the dermis and epidermis. About 15% of the epidermal dendritic cells expressing 4F7 exhibited Birbeck granules, the other Birbeck granule-negative cells resembled indeterminate dendritic cells (IDCs). The dermal and epidermal 4F7+ cells could be highly (98%) enriched with 4F7-labeled immunomagnetic particles. Transmission electron microscopic analysis of such preparations showed typical characteristics of dendritic cells with 50% or 100%, respectively, of these cells expressing Ia molecules on their cell membrane. The results suggest that the 4F7 epitope is expressed on dendritic cells related to Langerhans cells and is upregulated by an inflammatory stimulus.

Animals↗
PubMed1993

A 30-year follow-up study of the sons of alcoholic men.

The nature-nurture question in the etiology of alcoholism is discussed. The research results from twin and adoption studies indicate a considerable genetic (= biological) component in the etiology of alcoholism. A longitudinal high-risk study of alcoholism is presented. The sons of alcoholic men and matched controls have been followed prospectively since before birth. The main results from previous phases of the study and a recent 30-year follow-up assessment are presented.

Adolescent↗
PubMed1992

Immunohistological and immunoelectron microscopic identification of TNF alpha in normal human and murine epidermis.

The presence, distribution and cellular localization of tumour necrosis factor-alpha (TNF alpha) were investigated in normal human and murine epidermis using immunohistological and immunoelectron microscopic methods with monoclonal and polyclonal antibodies. The immunostaining revealed an intercellular plasma membrane and cytoplasmic labelling of the epidermal keratinocytes, but no labelling of Langerhans cells, melanocytes and Merkel cells. Large amounts of TNF alpha were regularly found in the sebaceous glands. These findings demonstrate that epidermal keratinocytes and especially sebocytes produce and release TNF alpha and that this keratinocyte-derived cytokine may be important for the structural and functional homeostasis of normal epidermis.

Adult↗
PubMed1992

Contact allergens modulate the expression of MHC class II molecules on murine epidermal Langerhans cells by endocytotic mechanisms.

MHC class II molecules play an important role during the sensitization phase of allergic contact dermatitis. To study the influence of contact allergens on the expression of these molecules by murine epidermal Langerhans cells (LC), we performed a flow-cytofluorometric analysis of the Ia-antigen expression after in vivo application of contact allergens. A distinct decrease in the Ia-antigen expression of the entire LC population was noticed 3 h after in vivo application of the contact allergen 2,4-dinitrofluorobenzene (DNFB). This decrease was transient and balanced 24 h after in vivo application of DNFB. A downregulation was also detectable after in vivo application of the contact allergens 1-chloro-2,4-dinitrobenzene (DNCB), oxazolone, K2Cr2O7, 2,4,6-trinitrochlorobenzene (TNCB), and toxic concentrations of the irritant compound sodium dodecyl sulfate (SDS). In vitro studies showed that freshly prepared as well as 3-d cultured LC downregulated their Ia-antigen expression in the presence of DNFB, which was used as a model compound. This decrease was not inhibited by the MHC class II molecule transport-inhibitor brefeldin A nor by the ionophore monensin. The inhibition of receptor-mediated endocytosis with hypertonic media (0.45 M sucrose) abolished the DNFB-mediated downregulation of Ia-antigen expression. An accelerated clearance of cell-surface-expressed antibody-labeled IA molecules was detectable in the presence of DNFB. Internalization studies carried out with peroxidase-labeled anti-IA-antibody complexes showed remarkable alterations in the intracellular distribution of endocytosed material under the influence of subtoxic concentrations of DNFB, DNCB, K2Cr2O7, and TNCB. The irritant substance sodium dodecyl sulfate (SDS) influenced the intracellular distribution pattern of internalized material only when used in toxic concentrations. An augmented participation of MHC class II molecules in endocytotic processes is mediated by reactive substances like contact allergens and might contribute to the processing and presentation of these compounds.

Allergens↗
PubMed1992

Increased level of intracellular MHC class II molecules in murine Langerhans cells following in vivo and in vitro administration of contact allergens.

Treatment of murine Langerhans cells (LC) with contact allergens results in increased internalization of cell membrane constituents and therefore in depressed cell-surface expression of major histocompatibility complex (MHC) class II molecules during the first hours after haptenization. In this presentation we show that this downregulation of cell-surface-expressed Ia-antigens is accompanied by an augmentation of the intracellular pool of MHC class II molecules. Rat MoAb 2G9 was developed, which recognizes IA and IE molecules of the d-haplotype. This MoAb competes with the murine MoAb MK-D6 for binding sites to IAd-molecules. After blocking the cell-surface-expressed molecules with 2G9 and permeabilizing the cell membranes this allowed us to measure selectively the intracellular amount of IA molecules by double immunofluorescence staining and flow cytometric analysis. Cell-surface expression of IA molecules was found to be depressed but their internal pool was significantly elevated following in vivo treatment with the contact allergens DNFB, DNCB, oxazolone, and K2Cr2O7 for 3 h. In vitro culture of freshly prepared LC in the presence of 1 microgram/ml DNFB yielded similar results. Blocking of protein biosynthesis with cycloheximide did not prevent this intracellular class II accumulation. An augmented representation of internalized class II molecules in haptenized LC might play an important role in the presentation of contact allergens.

Administration, Cutaneous↗
PubMed1992

A novel monoclonal antibody to a distinct subset of cutaneous dendritic cells.

A monoclonal antibody was generated by immunizing rats with Langerhans cell (LC)-enriched epidermal cells obtained from BALB/c mouse earskin after epicutaneous application of the contact sensitizer 2,4-dinitrofluorobenzene (DNFB). The antibody 4F7 detects in normal mouse skin, few dermal cells showing the morphologic, phenotypic, and functional properties of accessory dendritic cells, but lacking Birbeck granules. The capacity to stimulate allogenic T cells in the mixed leucocyte reaction resembles that of freshly isolated LCs. After DNFB application, an increased number of 4F7+ dendritic cells are found in the dermis and, in addition, some labeled dendritic cells occur in the epidermis. Some of the latter cells exhibit cytoplasmic Birbeck granules. Remarkably, there is no increase of the 4F7+ cells in the regional lymph nodes after DNFB treatment. These data suggest that the 4F7 antibody labels distinct dendritic cells of the mouse skin that are involved in the mediation of contact sensitization and probably represent immature LCs.

Animals↗
PubMed1992

Induction of inflammatory cytokines in murine keratinocytes upon in vivo stimulation with contact sensitizers and tolerizing analogues.

In order to elucidate the role of keratinocytes (KCs) in the induction of contact sensitivity, we applied various contact sensitizers [2,4-dinitrofluorobenzene (DNFB), urushiol, 3-n-pentadecylcatechol (PDC), 4-ethoxymethylene-2-phenyloxazol-5-one (oxazolone)] and tolerizing compounds [2,4-dinitrothiocyanobenzene (DNTB), 5-methyl-3-n-pentadecyl-catechol (5-Me-PDC)] onto the earskin of non-sensitized Balb/c mice. In addition, we applied croton oil as a non-sensitizing, but stimulatory agent. Cytokine production was demonstrated by Northern blot hybridization of the total cellular RNA extracted from epidermal cells depleted by Langerhans cells and Thy 1+ dendritic cells using radiolabeled DNA probes encoding for the murine cytokines IL-1 alpha, -2, -3, -4, TNF alpha, IFN tau, GM-CSF and G-CSF. From all cytokines tested, TNF alpha and IL-1 alpha were markedly increased upon in vivo stimulation with contact sensitizers and also after application of croton oil. Both light and electron microscopic immunostaining with a polyclonal and monoclonal antibody demonstrated the presence of TNF alpha in the epidermis. This staining was most pronounced in KCs of the suprabasal epidermis upon application of contact sensitizers or croton oil, but not with tolerizing analogues. Using a functional assay significantly more TNF alpha was found in the supernatants of KCs treated in vitro with DNFB or LPS than with DNTB. GM-CSF was found in untreated epidermis as well as in stimulated cells. The results suggest that the sensitizing properties of contact sensitizers may partly be dependent on their ability to induce proinflammatory mediators. The induction and release of TNF alpha and IL-1 alpha in KCs by contact sensitizers may play an important role in the early response to immunogenic or inflammatory signals in vivo, whereby tolerance induction seems to be less dependent on these cytokines.

Animals↗
PubMed1992

Increased expression of ICAM-1, E-selectin, and VCAM-1 by cultured human endothelial cells upon exposure to haptens.

Contact allergens induce several accessory signals which promote the activation of antigen-specific T cells. One of these signals is the increased expression of adhesion molecules on antigen-presenting cells and endothelial cells. Epicutaneous application of non-toxic doses of 2,4-dinitrofluorobenzene (DNFB) onto the skin of non-sensitized individuals elicited progressive staining for ICAM-1 on dermal microvascular endothelial cells. To elucidate the question of whether contact allergens can act directly on endothelial cells to elevate their expression of surface structures that bind leukocytes, confluent monolayers of human umbilical vein endothelial cells were incubated with the contact allergens NiSO4, CoSO4 or DNFB. The ICAM-1, E-selectin and HLA-DR expression were quantified by immunofluorescence flow cytometric analysis. Furthermore VCAM-1, E-selectin and ICAM-1 transcription were demonstrated by Northern blot hybridization. Constitutive ICAM-1 expression on HUVEC increased similarly to that obtained after LPS (20 micrograms/ml) stimulation after 4 and 24 hours of incubation with 1 or 2 mM NiSO4 or CoSO4, respectively. Pulse-stimulation with 100 or 500 nM DNFB resulted in a modest but significant increase of ICAM-1-positive cells. E-selectin and VCAM-1 were not expressed on untreated HUVEC; 4 to 6 hours exposure to nickel sulfate and LPS resulted in a potent induction of E-selectin and VCAM-1 expression. DNFB and PMA had no significant influence on VCAM-1 expression. None of the tested contact allergens was capable of inducing HLA-DR expression on EC at 48 to 72 hours. Enhanced expression of adhesion molecules may be an important early unspecific mechanism for induction and elicitation of a contact dermatitis.

Cell Adhesion Molecules↗
PubMed1992

99mTc-HMPAO-SPECT with acetazolamide challenge to detect hemodynamic compromise in occlusive cerebrovascular disease.

BACKGROUND AND PURPOSE: Insufficiency of collateral supply may lead to low-flow infarcts in severe occlusive cerebrovascular disease. The aim of this study was to evaluate the feasibility of technetium-99m-labeled hexamethylpropyleneamine oxime (99mTc-HMPAO) single-photon emission computed tomography (SPECT) to assess hemodynamic compromise in the anterior circulation. METHODS: Cerebral blood flow before and after 1 g acetazolamide was analyzed by 99mTc-HMPAO-SPECT in 21 symptomatic patients with documented extracranial obstructions. SPECT findings were correlated with the results of angiography, transcranial Doppler sonography, and computed tomographic scan. RESULTS: The acetazolamide-induced increase of cerebral blood flow could be reliably monitored by increase of cerebral 99mTc-HMPAO uptake, which varied between 11.4% and 47.6% in the less-affected hemisphere. Increment of hemispheric side-to-side asymmetry of tracer uptake after drug challenge revealed significant restriction of regional vasoreactivity in 11 patients. Agreement in assessing hemodynamic compromise was reached in 81% of patients with ophthalmic artery collaterals on angiography (p < 0.001), in 76% with low-flow infarcts on computed tomographic scan (p < 0.01), and in 91% with markedly reduced flow velocities on transcranial Doppler (p < 0.0001). One patient developed a low-flow infarct in the area predicted by SPECT during follow up. CONCLUSIONS: We conclude that 99mTc-HMPAO-SPECT with acetazolamide challenge is a useful method for assessment of the adequacy of hemispheric collateral pathways in patients with severe occlusive cerebrovascular disease.

Acetazolamide↗
PubMed1991

[Alcohol abusers in the psychiatric emergency departments in Copenhagen and Frederiksberg].

On the basis of a prospective random sample investigation of 611 alcohol-related visits to the four psychiatric emergency units of the City of Copenhagen, demographic variables, referral sources and dispositions of treatment are described. On every 10th day throughout 1985 all visits were registered. The distribution of all variables except age and sex deviate significantly from those of non-alcohol-related visits. Thus fewer alcoholics cohabit and more are divorced. 25% of the alcohol-related visits resulted in an overnight stay in the unit, while 10% resulted in admission to the psychiatric ward. For non-alcohol-related visits the proportions were the reverse.

Adult↗
PubMed1991

Biochemical properties of MHC class II molecules endogenously synthesized and expressed by mouse Langerhans cells.

The cell surface expression and biosynthesis of Langerhans cells (LC)-derived major histocompatibility complex (MHC) class II molecules from epidermal cells (EC) prepared freshly and cultured for up to 3 days was investigated. Based on the constitutive expression of MHC class II determinants by LC, a panning and magnetic bead selection procedure was employed, yielding 65% and 86% of I-A+ cells, respectively. Phenotypical and cytochemical examinations revealed that the two LC preparations were free of contaminating macrophages as well as B and T cells. Freshly prepared enriched LC were highly efficient in the stimulation of protein antigen-specific T cell clones, while LC purified from short-term cultured EC suspensions proved to be more efficient allogeneic stimulator cells than fresh LC. Comparative analysis of LC obtained from freshly prepared and from short-term-cultured EC preparations indicated an up-regulation of MHC class II determinants during short-term culture. Radioiodination analysis of LC selected by magnetic beads demonstrated prominent class II alpha and beta chain signals with only a minute fraction of invariant chains p35 and p45 being expressed at the cell surface. Unlike class II complexes derived from B cells, those from LC contained invariant chain fragment p20 in association with alpha/beta heterodimers at the plasma membrane. No qualitative differences between freshly isolated and 3-day cultured LC in cell surface expressed MHC class II components were detectable. Metabolic labeling with subsequent two-dimensional electrophoresis revealed distinct features of LC-derived MHC class II molecules with a high proportion of invariant chains in particular gamma and p40 and their extensive sialylation. While fresh and 1-day cultured LC exhibited appreciable levels of newly synthesized class II molecules, a dramatic down-regulation in class II and invariant chain synthesis was measured after 3 days of continuous in vitro culture.

Animals↗