[Granuloma anulare disseminatum as a rare side effect of allopurinol]

During long-term therapy of hyperuricaemia with allopurinol (300 mg/d) two patients developed generalized granuloma annulare. The diagnoses were confirmed by histology; concomitant diseases, especially diabetes mellitus, were not detectable. Following discontinuation of allopurinol therapy, cutaneous granulomas healed without relapse. Hyperuricaemia could be controlled by low-purine diet and medication avoiding allopurinol. The clinical history of our two patients suggested a causal connection between allopurinol therapy and generalized granuloma annulare. For this reason we rate the development of this disease in both cases as a rare but significant side effect of allopurinol. This should give rise to critical assessment of concomitant drug therapy during development of generalized granuloma annulare.

A new method for phenotyping proliferating cell nuclear antigen positive cells using flow cytometry: implications for analysis of the immune response in vivo

The incorporation of radioactive nucleotides into newly synthesized DNA has been established as a standard method for the detection of proliferation in eucaryotic cells. Unfortunately the use of this method makes it harder to obtain information on the phenotype of proliferating cells in mixed cell populations. For this reason we established a flow-cytometric approach employing a monoclonal antibody specific for murine as well as human proliferating cell nuclear antigen (PCNA) and a double labeling technique for detection of cell membrane-expressed phenotypic markers. The efficiency of this immunostaining procedure was confirmed by simultaneous and highly specific detection of PCNA in nuclear structures as well as cell membrane-expressed antigens using cytological techniques. In vitro experiments with mitogen- and alloantigen-stimulated murine lymph node cells (LNC) and human peripheral blood mononuclear leukocytes (PBML) revealed a good correlation of total [3H]thymidine incorporation into DNA and expression of PCNA. For the analysis of proliferating cells activated in vivo the method was employed to evaluate the local lymph node assay which assesses the allergenicity of small chemicals. LNC prepared from the cervical lymph nodes of mice treated on 4 consecutive days with sensitizing concentrations of the contact allergens oxazolone, TNCB and DNFB as well as the irritants benzoic acid and SLS in comparison to the solvent control showed a dramatic increase in the total amount of proliferating cells for contact allergen-treated animals in comparison to the solvent control and irritant-treated mice. In addition a detailed phenotyping of the proliferating cell populations was possible. This approach offers an easy to perform, non-radioactive method for the assessment of proliferation of murine as well as human leukocytes in vitro and especially in vivo and will be of great advantage for situations where the phenotype of proliferating cellular subsets in heterogeneous populations is of interest.

In vitro analysis of the phenotypical and functional properties of the 4F7+ cutaneous accessory dendritic cell

The monoclonal antibody 4F7 detects a molecule on dermal and epidermal Ia+ dendritic cells (DCs), and some of these cells are Birbeck granule-containing cells. Here we report on the phenotypical and functional characteristics of these cells which were highly enriched by 4F7-labelled immunomagnetic beads. The ultrastructural, immunocytochemical and cytochemical analyses of these preparations showed cells with the typical characteristics of DCs. The cells were found to express the DC marker NLDC145, but not 33D1. The C3bi receptor and marker F4/80 were only expressed by epidermal 4F7+ cells. The capacity of freshly isolated 4F7+ epidermal and dermal DCs to activate allogeneic T cells in a mixed leukocyte reaction was similar to the capacity of freshly isolated Langerhans cells. After culture, the epidermal cells showed a 4-5-fold increase in stimulation, whereas no difference was observed in the 4F7+ dermal DCs. We conclude that this new antibody recognizes a function-associated molecule on cutaneous DCs which are phenotypically and functionally related to Langerhans cells. The 4F7+ DCs may be precursors of epidermal Langerhans cells.

Freshly isolated mouse 4F7+ splenic dendritic cells process and present exogenous antigens to T cells

The antibody 4F7 was reported to recognize an epitope expressed on dendritic cells (DC) from various tissues. To study the ability of splenic 4F7+ dendritic cells to process antigen for presentation to CD4+ T cells, DC were enriched using a separation procedure avoiding overnight culture which could lead to an altered phenotype. These DC were used as antigen-presenting cells (APC) in stimulation cultures of major histocompatibility complex class II-restricted T cells. It was found that they induce antigen-dependent lymphokine production by T cells and therefore could present exogenous antigens. These processing takes place intracellularly, because fixation abrogates presentation to T cells. Moreover, antigen presentation needs intracellular processing within endo- or lysosomes as chloroquine-treatment prevents T cell activation. Titration of APC numbers revealed that contaminating APC most likely did not account for antigen-specific T cell activation by DC. No evidence was found for release of antigenic peptides or for partial antigen processing possibly done by cell surface located enzymes on DC. In conclusion, these results indicate that freshly enriched DC are able to process antigens similarly to other APC.

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.

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.

Induction of hapten-specific tolerance by interleukin 10 in vivo

Interleukin 10 (IL-10) is released during the induction phase of contact sensitivity and was shown in prior functional studies to convert epidermal Langerhans cells (LC) from potent inducers of primary immune responses to specifically tolerizing cells in vitro. To investigate whether IL-10 also subserves the function of a tolerizing agent in vivo ears of BALB/c or C3H mice were injected intradermally with 1-2 micrograms of recombinant mouse (rm)IL-10 8 h before epicutaneous application of 3% trinitrochlorobenzene (TNCB; a contact allergen). As a control, mice were injected with phosphate-buffered saline or IL-10 plus neutralizing amounts of anti-IL-10 mAb. 5 d later, mice were challenged with 1% TNCB on contralateral ears and ear swelling response was measured 24 h later. Whereas control-treated mice showed a normal ear swelling response to epicutaneous challenge (delta mm-2 = 25 +/- 5), ear swelling response of IL-10-treated animals was significantly inhibited (delta mm-2 = 3 +/- 2). Coinjection of IL-10-specific mAb together with rmIL-10 completely abrogated this effect. To differentiate between a state of nonresponsiveness and induction of tolerance by IL-10, mice initially treated with IL-10 and TNCB were resensitized with 3% TNCB in the absence of any treatment after 14 d of rest (group 1). Again mice were challenged 5 d later and ear swelling responses were tested. Whereas control mice treated with allergen alone (group 2) showed a good swelling response (delta mm-2 = 28 +/- 6), IL-10-treated mice (group 1) showed a minimal response towards application of allergen (delta mm-2 = 4 +/- 2). To show that anergy induction by IL-10 was antigen-specific, mice initially treated with IL-10 plus TNCB were exposed to 0.5% dinitrofluorobenzene (DNFB) 14 d later (group 1). After challenge with 0.1% DNFB, IL-10-treated mice showed an ear swelling response (delta mm-2 = 13 +/- 3; group 1) similar to that of control mice only sensitized with DNFB (delta mm-2 = 14 +/- 3; group 3). In an attempt to show the induction of antigen-specific tolerance in these mice in vitro, regional lymph nodes of mice initially treated with TNCB plus IL-10 (group 1) and control-treated mice (groups 2 and 3) were prepared and cultured in the presence of TNBS, dinitrobenzene sulfonate (DNBS), or medium to measure antigen-specific proliferation.(ABSTRACT TRUNCATED AT 400 WORDS)

An in vitro test for endocytotic activation of murine epidermal Langerhans cells under the influence of contact allergens

Several in vivo and in vitro studies have shown that contact sensitizing agents induce enhanced internalization of cell membrane constituents by epidermal Langerhans cells (LC). However the intracellular distribution of the internalized material has not yet been clearly defined. For this reason we investigated the uptake of gold-labeled antibodies against MHC class II molecules by cultured murine LC under the influence of various contact sensitizing agents, non-sensitizing analogues, and irritants. Antigen-antibody complexes were visualized by light microscopy using the silver enhancement technique and by pre-embedding electron microscopy. Viability was monitored by staining dead cells with propidium iodide. For light-microscopic evaluation of the intracellular distribution pattern of gold particles, a stimulation index was defined and used for the assessment of endocytotic activation. Untreated and solvent treated (control) cells exhibited an accumulation of internalized gold complexes into large aggregates composed of few intracellular vesicles. Cytoplasmic staining was absent and few gold particles were detectable in the endocytotic organelles under these conditions. In contrast to the non-sensitizing compounds DCNB and DNBSO3, which had no effect at all, treatment with subtoxic concentrations of the contact sensitizing agents DNFB, DNCB, TNCB, K2Cr2O7, NISO4 and p-phenylenediamine resulted in diffuse intracellular staining which was most pronounced in the submembraneous region. This was due to the numerous endocytotic vesicles which were closely associated with the cell membrane. Consequently a significant increase in the stimulation index was noted for these compounds. An irritant such as sodium lauryl sulphate used in subtoxic concentrations did not influence the intracellular distribution of internalized gold particles whereas toxic amounts of this compound induced a diffuse intracellular staining pattern indicative of membrane destruction. This approach represents a practical and reliable test for endocytotic activation of murine LC and may be useful for in vitro tests of the activating and possibly sensitizing properties of new chemical compounds.

Familial alcoholism: family, twin adoption and high risk studies

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.

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.

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.

[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.

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.

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.

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.

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.

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.

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.

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.

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.