The human hair follicle immune system: cellular composition and immune privilege

The immunology of the hair follicle, its relationship with the 'skin immune system' and its role in hair diseases remain biologically intriguing and clinically important. In this study, we analysed the immunoreactivity patterns of 15 immunodermatological markers to determine the cellular composition and immune privilege of the human hair follicle immune system in anagen VI (growth phase). The most prominent cells located in or around the hair follicle were Langerhans cells, CD4+ or CD8+ T cells, macrophages and mast cells, whereas B cells, natural killer cells and gammadelta T cells were found very rarely. Langerhans cells (CD1a+, major histocompatibility complex, MHC class II+), and T cells (CD4+ or CD8+) were predominantly distributed in the distal hair follicle epithelium, whereas macrophages (CD68+, MHC class II+) and mast cells (Giemsa+) were located in the perifollicular connective tissue sheath. Transmission electron microscopy confirmed low numbers of immune cells in the proximal hair follicle epithelium, and very few macrophages and Langerhans cells were seen in the dermal papilla. Melanophages were observed in the connective tissue sheath and dermal papilla. MHC class I (HLA-A, -B, -C) and beta2-microglobulin immunoreactivity was found on most skin cells, but was substantially reduced on isthmus keratinocytes and virtually absent in the proximal hair follicle epithelium. Apart from the absence of Fas ligand immunoreactivity, the sharply reduced numbers of T cells and Langerhans cells, and the virtual absence of MHC class I expression all suggest that the anagen proximal hair follicle constitutes an area of immune privilege within the hair follicle immune system, whose collapse may be crucial for the pathogenesis of alopecia areata.

Mast cells and their mediators in cutaneous wound healing--active participants or innocent bystanders?

Mast cells are traditionally viewed as effector cells of immediate type hypersensitivity reactions. There is, however, a growing body of evidence that the cells might play an important role in the maintenance of tissue homeostasis and repair. We here present our own data and those from the literature elucidating the possible role of mast cells during wound healing. Studies on the fate of mast cells in scars of varying ages suggest that these cells degranulate during wounding, with a marked decrease of chymase-positive cells, although the total number of cells does not decrease, based on SCF-receptor staining. Mast cells contain a plethora of preformed mediators like heparin, histamine, tryptase, chymase, VEGF and TNF-alpha which, on release during the initial stages of wound healing, affect bleeding and subsequent coagulation and acute inflammation. Various additional vasoactive and chemotactic, rapidly generated mediators (C3a, C5a, LTB4, LTC4, PAF) will contribute to these processes, whereas mast cell-derived proinflammatory and growth promoting peptide mediators (VEGF, FGF-2, PDGF, TGF-beta, NGF, IL-4, IL-8) contribute to neoangiogenesis, fibrinogenesis or re-epithelization during the repair process. The increasing number of tryptase-positive mast cells in older scars suggest that these cells continue to be exposed to specific chemotactic, growth- and differentiation-promoting factors throughout the process of tissue remodelling. All these data indicate that mast cells contribute in a major way to wound healing. their role as potential initiators of or as contributors to this process, compared to other cell types, will however have to be further elucidated.

Psychosocial stress in tree shrews: clomipramine counteracts behavioral and endocrine changes

Male tree shrews (Tupaia belangeri) provide an animal model to study the neurobehavioral consequences of chronic psychosocial stress. When living in visual and olfactory contact with a male conspecific by which it has been defeated, the subordinante tree shrew shows dramatic behavioral, physiological, and neuroendocrine changes. Because the over all pattern of these changes resemble a depression-like symptomatology, we investigated to what extent the behavioral and endocrine changes in subordinate animals can be reversed by treatment with the tricyclic antidepressant clomipramine. In the present study, animals were subjected to a 10-day period of psychosocial conflict to elicit stress-induced behavioral and endocrine alterations before the onset of drug treatment, and psychosocial stress continued throughout the treatment period of 30 days. Clomipramine was administered orally once daily at a dose of 50 mg/kg. The drug had a time-dependent restorative influence on marking and grooming behavior, locomotor activity, risk assessment, as well as on urinary cortisol and norepinephrine excretion. It, thus, appears that the clomipramine treatment counteracts the behavioral and endocrine effects of chronic psychosocial stress in tree shrews, and the time course of recovery corresponds closely to that observed when treating depressed patients in the clinic.

Upregulation of TNF-alpha and IL-3 expression in lesional and uninvolved skin in different types of urticaria

BACKGROUND

Although mast cells are known to secrete a broad spectrum of proinflammatory and immunomodulatory cytokines, the role of these molecules in mast cell-dependent cutaneous inflammation is not clear.

OBJECTIVE

We decided to study biopsy specimens from lesional and nonlesional skin of patients with acute, chronic recurrent, delayed pressure, and cold urticaria; from fleeting wheals of prick test reactions to allergens; and from normal skin of nonallergic subjects.

METHODS

Cryostat sections were stained by immunohistochemistry with antibodies against IL-3, IL-8, TNF-alpha, and mast cell-specific tryptase. In serial sections with tryptase and each cytokine, reactivity of mast cells was studied as well.

RESULTS

Compared with normal skin and prick test reactions, immunoreactivity for TNF-alpha and IL-3 was significantly increased on endothelial and perivascular cells of the upper dermis in all urticaria lesions. In nonlesional skin comparable upregulation was noted on endothelial cells and for TNF-alpha on perivascular cells of patients with delayed pressure urticaria. In addition, TNF-alpha was expressed throughout the epidermis in lesional and nonlesional skin of patients with all types of urticaria, but not in normal control subjects. Sequential biopsy specimens from patients with cold urticaria showed upregulation of TNF-alpha and IL-3 on endothelial cells 30 minutes after elicitation of lesions with an ice cube. In contrast to these findings, epidermal immunoreactivity, as well as endothelial and perivascular cell expression of IL-8, were only slightly altered in urticaria compared with normal skin. In sequentially stained sections, few tryptase-positive mast cells reacted to TNF-alpha, few reacted to IL-3 in pressure urticaria only, and practically none stained for IL-8.

CONCLUSION

These findings suggest that the cytokines studied here are involved in the pathology of urticaria, possibly by inducing subthreshold inflammation in endothelial cells of uninvolved skin.

Clusters of perifollicular macrophages in normal murine skin: physiological degeneration of selected hair follicles by programmed organ deletion

In back skin sections from adolescent C57BL/6 mice, regularly distributed, perifollicular inflammatory cell clusters (PICC) were found located around the distal noncycling portion of about 2% of all hair follicles examined. The PICC and the affected hair follicles were characterized during spontaneously developed or induced hair cycle stages, using antibodies against MHC Class II, F4/80, ER-MP23, NLDC 145, CD4, CD8, gammadeltaTCR, IL-1 receptor, and ICAM-1. PICC consisted predominantly of macrophages (MAC), accompanied by a few CD4+ cells, whereas gammadeltaTCR+ and CD8+ cells were absent. During anagen and catagen, some of the PICC+ hair follicles showed variable degenerative phenomena reminiscent of scarring alopecia: thickened basement membrane, ectopic MHC II expression, MAC infiltration into the follicle epithelium, and signs of keratinocyte apoptosis. Loss of distal outer root sheath keratinocytes was detected in 10% of PICC+ hair follicles (0.2% of all hair follicles). Because PICC were located in the vicinity of the bulge region, MAC-dependent damage to follicle stem cells might eventually lead to follicle degeneration. These perifollicular MAC clusters around selected hair follicles may indicate the existence of a physiological program of MAC-dependent controlled follicle degeneration by which damaged or malfunctioning follicles are removed by programmed organ deletion (POD).

Mast cell chymase and tryptase during tissue turnover: analysis on in vitro mitogenesis of fibroblasts and keratinocytes and alterations in cutaneous scars

In order to shed further light on the potential role of mast cells during tissue turnover, we have investigated the number of mast cells containing only tryptase and those storing both tryptase and chymase by enzyme histochemistry in normal versus healing skin. Furthermore, we have studied the in vitro effect of these enzymes on the mitogenesis of subconfluent quiescent fibroblast and HaCaT keratinocyte cultures, using flowcytometric DNA analysis. Chymase-containing mast cell numbers were markedly decreased in scars (P<0.001), whereas the overall number of tryptase-containing mast cells was not decreased, although these cells were smaller and stained more faintly in scars. Chymase (5 to 300 mU/ml) induced a marked, dose-dependent in vitro mitogenic response in 3T3 fibroblasts, whereas the effects of tryptase, at up to 60 nM, were only moderate, compared to the known fibroblast mitogens EGF, TGF-alpha, alpha-thrombin and trypsin at optimal concentrations. Coincubation of either protease with EGF or alpha-thrombin had additive effects. In contrast to fibroblasts, keratinocytes showed only minor mitogenic responses to tryptase and chymase, also in comparison to other known mitogenic stimuli, and responses to EGF and alpha-thrombin were inhibited on costimulation of cells with the proteases. These findings document for the first time a potential role of mast cell chymase in connective tissue repair, with tryptase being less active on fibroblasts, and with inhibitory effects of both mast cell proteases on keratinocytes.

Altered expression of mast cell chymase and tryptase and of c-Kit in human cutaneous scar tissue

In order to explore a possible involvement of mast cells during human wound healing, we studied sections from scars (4-369-d-old) (N = 20) and normal skin (N = 10) for mast-cell-specific tryptase and chymase by enzyme histochemistry, for the stem cell factor receptor c-Kit and the melanosomal marker TA99 by immunohistochemistry, and for simultaneous c-Kit expression and avidin fluorescence by double staining. Enzyme activities and mRNA expression were also studied in tissue extracts. Chymase-reactive mast cell numbers as well as chymase activity and mRNA expression were reduced in all scars, whereas overall numbers of tryptase-reactive cells did not differ from normal skin, although tryptase activity and mRNA expression were increased in scar extracts. In contrast, numbers of c-Kit positive cells were significantly increased in old scars, and in the mid and lower dermis of all scars. A marked reduction of c-Kit reactivity was noted, however, in avidin-positive dermal mast cells and in epidermal basal cells, despite unchanged numbers of melanosome-positive cells, with an associated overall decrease of c-Kit mRNA in scar extracts. These data thus show that numbers of resident mast cells are very low in human cutaneous scars, suggesting massive mediator release from these cells into fresh wounds. Downregulation of stem cell factor receptors may also prevent these cells from increasing in number even in old scars. Instead, scar tissue is populated by a mast cell subpopulation that is chymase-, avidin-, tryptase +, c-Kit +, reflecting most probably an increased immigration and/or proliferation of immature mast cells and their precursors.

[Scar forming alopecia. Comments on classification, differential diagnosis and pathobiology]

Numerous different diseases lead to scarring alopecia with irreversible follicular destruction as a common ending. Current classifications are based on clinical, histopathological or prognostic parameters, as well as on pathogenetic criteria which allow only a rough assessment because the precise mechanisms leading to scarring alopecia are still unknown. Inadequacies of the established classifications are obvious when regarding special forms of scarring alopecia like lichen planopilaris or pseudopelade Brocq. In order to develop more satisfying classifications, recent insights into biology and pathology of the hair follicle and follicular cycling have to be considered. The most important structures for the survival of the hair follicle are the epithelial stem cells which reside in the follicular bulge and the fibroblasts of the dermal papilla including the molecular communication between these two cell populations. Research in the field of scarring alopecia should aim at defining the pathological processes on any of the above mentioned levels which will lead to an irreversible damage of the hair follicle thus allowing the development of new therapeutic agents.

Automated determination of paroxetine and its main metabolite by column switching and on-line high-performance liquid chromatography

An automated column-switching method coupled to isocratic high-performance liquid chromatography has been developed for simultaneous determination of blood levels of paroxetine and its nonconjugated main metabolite BRL 36610. The lower limits of detection were 9-15 nmol/L (3-5 ng/ml) and linearity between drug concentration and detector response was found for 0-1,500 nmol/L (0-500 ng/ml). The method could be applied to the analysis of serum samples obtained from depressed patients who were treated with daily oral doses of 20 or 40 mg of paroxetine. After the 20-mg dose, the mean blood level of paroxetine was 69 nM (23 ng/ml), whereas the metabolite BRL 36610 was detectable in only one of 5 samples. Co-medication of paroxetine with imipramine increased the blood levels of imipramine, desipramine, and paroxetine thus indicating drug interactions.

Expression of mast cell growth modulating and chemotactic factors and their receptors in human cutaneous scars

In order to explore possible mechanisms involved in the previously documented turnover of mast cell subpopulations in human cutaneous scars, we have examined selected factors known to stimulate and/or modulate mast cell hyperplasia (SCF, NGF, TGFbeta1, GM-CSF) and their receptors in human cutaneous scar tissue. On immunohistochemistry, numbers of SCF- and TGFbeta1-positive cells were significantly increased in the epidermis and throughout the dermis in scars (n = 27) of varying ages (4-369 d old), compared with normal skin (n = 12). Furthermore, TRbetaRI, II, and the NGF-p75 receptors were significantly increased in the epidermis, TRbetaRI and NGF-TrkA throughout the dermis, and TRbetaRII, NGF-p75, and GM-CSFR only in the mid- and lower dermis of scars. NGF and GM-CSF expression was in contrast scarce and weak, with no differences between normal skin and scars. In tissue extracts, mRNA levels of SCF, TGFbeta1, TRbetaI and II, and both NGF-receptors, but not GM-CSFR, were significantly increased as well. TRbetaI and II were identified in up to 90% and 83%, respectively, of isolated normal skin mast cells on flow cytometry, and GM-CSFR and NGFR-p75 were identified on 70% and 73%, respectively, of avidin-positive normal mast cells on double immunofluorescence microscopy. As described before for the SCF receptor KIT, GM-CSFR and NGFR-p75 were partly or entirely downregulated on avidin-positive mast cells in scars. The marked upregulation of TGFbeta1, its type I and II receptors, and SCF suggest that these factors play a major role in the orchestration of mast cell increase in human cutaneous scars whereas the role of NGF and GM-CSF is less clear, despite the significant upregulation of their receptors.

Phacomatosis pigmentokeratotica: a patient with the rare melanocytic-epidermal twin nevus syndrome

We describe a 10-year-old girl affected with a speckled lentiginous nevus and an epidermal nevus of the organoid type on corresponding parts of the body. On histopathological examination, the lesions showed epidermal hyperpigmentation and melanocytic hyperplasia on the one hand and verrucous epidermal acanthosis with sebaceous hyperplasia on the other hand. Except for a minor deviation of the spine, the patient had no obvious extracutaneous symptoms. Happle et al. have recently interpreted the rare co-occurrence of these two types of nevi in spatial proximity as an example of twin spotting in human skin and proposed the name 'phacomatosis pigmentokeratotica'. In most cases, additional skeletal or neurological anomalies are found. These are dissimilar from the extracutaneous symptoms of the sebaceous nevus syndrome, from which phacomatosis pigmentokeratotica should be distinguished. Molecular studies are needed to prove the concept of twin spotting and to reveal a link to the extracutaneous manifestations.

Synaptic ribbons, spheres and intermediate structures in the developing rat retina

The present study was conducted to investigate the qualitative and quantitative development of synaptic bodies in retinae of Wistar rats during postnatal days 4-28. In addition, the effects of different light regimens and of eye pigmentation on SB numbers were studied. Synaptic bodies were counted and measured in the outer plexiform layer of retinal tissue fixed and processed by routine electron microscopical techniques. At postnatal days 4 and 5, retinae showed only few synaptic bodies. The main numerical development of synaptic bodies occurred between postnatal days 4 and 9, numbers remaining more or less constant thereafter. The intracellular location of synaptic ribbons changed from predominantly cytoplasmic sites to positions at the membrane. In Wistar rats of postnatal day 15 held under a light/dark regimen, synaptic ribbon numbers and lengths were found to be significantly larger at night than at daytime. This was not observed in animals kept under constant darkness. In retinae of a pigmented rat strain, Brown Norway, total numbers of synaptic bodies were similar to those of Wistar rats, whereas the relative proportions of synaptic ribbons and spheres or sphere-like structures, respectively, differed between strains. These results are discussed with regard to synaptic body formation and regulation under the influence of light and eye pigmentation.

Adhesion molecules and cellular infiltrate: histology of urticaria

Urticarial reactions are characterized by dermal capillary dilatation and edema, associated with a variably intense mixed inflammatory infiltrate consisting of neutrophils, eosinophils, T-helper lymphocytes, and activated macrophages. Mast cell numbers are moderately increased by a factor of 2.4, in contrast to mastocytosis where numbers are much higher (5-48-fold increase). In urticarial vasculitis there is in addition endothelial damage, leukocytoclasia, and fibrin and complement deposition. The emigration of leukocytes is regulated by vasoactive and chemotactic mediators released firom mast cells, inducing a sequential upregulation of endothelial adhesion molecules (P-selectin, E-selectin, ICAM-1, and VCAM-1), of beta2-integrins on leukocytes, and of cytokines on endothelial, epithelial, and infiltrating cells. In nonlesional skin, there is also an increase of mast cells and an upregulation of endothelial adhesion molecules, probably due to molecules in the circulation of which P-selectin and TNFalpha have so far been demonstrated. Whereas these data provide a molecular basis for the understanding of variations in mast cell-dependent pathology, they underline the fact that they are not diagnostic for different types of urticaria, except for urticarial vasculitis and mastocytosis.

Crossreacting IgG antibodies against fox mite antigens in human scabies

Scabies continues to be an important parasitic disease of mammals. There remain, however, major gaps in the understanding of the human host immune response, and a simple diagnostic test is lacking. In contrast to human mites, red fox mites (Sarcoptes scabiei var. vulpis) can be collected easily and have been used, due to crossreactivity, for enzyme-linked immunosorbent assay (ELISA) studies in dogs and pigs. We wanted to investigate the possibility that crossreactivity might also exist for the human mite, and determined titers against fox mite antigens by ELISA in 41 patients with scabies. Specific IgG was significantly higher in patients with scabies than in healthy controls (P=0.01). The sensitivity was, however, only 48%, although it increased slightly during treatment (P=0.86). A positive correlation was also noted between disease duration and severity of infestation (r=0.5), with specific IgG titers increasing in parallel with severity of symptoms (P=0.01). Patients with symptomatic scabies for more than 4 weeks had furthermore significantly higher IgG titers than patients with a shorter duration of disease (P=0.007). In conclusion, these findings demonstrate IgG antibodies in human scabies that crossreact with fox mite antigens, thus encouraging the search for improved ELISAs with more specific mite antigens to produce a more sensitive detection system for scabies in humans.

[Successful treatment of chronic discoid lupus erythematosus with argon laser]

We report on a patient with chronic discoid lupus erythematosus who was treated with argon-laser. The patient suffered from long-standing lesions and had been pretreated with various drugs; with no or slight improvement. After a few argon-laser applications, the treated skin lesions improved dramatically while the untreated lesional skin showed continuous disease activity. Histological and immunohistological investigations of biopsies from treated and untreated lesional skin suggest that endothelial mechanisms play a role in the generation and maintenance of discoid lesions in lupus erythematosus. This is the first reported case of successful treatment of chronic discoid skin lesions of a lupus erythematosus patient with argon-laser.

Foreign-body granuloma and IgE-pseudolymphoma after multiple bee stings

We report a patient with an unusual combination of an eosinophilic foreign-body granuloma and a pseudolymphoma, with recurrent severe oedema on the forehead, after multiple bee stings. On immunohistology the foreign-body granuloma and lymphoid follicles reacted with monoclonal antibodies against the high- and low-affinity IgE receptors, and against IgE. Prick and intradermal tests with whole-body bee extracts showed positive immediate-type reactions. The eosinophilic granuloma formation and lymphoid follicles may have been induced by a combination of immune complex and cell-mediated hypersensitivity following antigen persistence. Although bee stings are common, as far as we are aware, this complex reaction pattern has not been reported previously.

Day- and nighttime content of monoamines and their metabolites in the pineal gland of rat and hamster

Day- and nighttime content of catecholamines, serotonin and their metabolites were measured in the pineal gland of Sprague-Dawley rats and Djungarian hamsters. In addition, monoamine turnover rates were determined in the hamster pineal gland following administration of alpha-methyl-p-tyrosine. Animals were decapitated in the middle of the light or dark period, respectively, and pineal tissue was analysed by high performance liquid chromatography with electrochemical detection. Pineals of both species exhibited day/night-differences in serotonin, 5-hydroxyindole-3-acetic acid and dopamine content. The hamster pineal gland further showed day/night differences in its content of epinephrine and 3-methoxy-4-hydroxyphenylethyleneglycol. The dopamine turnover rate was augmented at night, while norepinephrine turnover was constant. Immunohistochemical incubations of pineal paraffine sections showed fibers and terminals stained by antisera to tyrosine-hydroxylase (TH) and dopamine-beta-hydroxylase, and a few perikarya-like structures exhibiting TH immunoreactivity. The results support the view that dopamine, rather than only functioning as a norepinephrine precursor, is actively involved in the control of melatonin synthesis.

Decreased cutaneous expression of stem cell factor and of the p75NGF receptor in urticaria

BACKGROUND

Mast cells, the main effector cells in urticaria, have been reported to be increased in number in lesional and nonlesional skin of urticaria patients, but the underlying mechanisms have so far not been studied. Serum NGF has however, been reported to be increased in urticaria.

OBJECTIVES

We have therefore explored the potential involvement of known mast cell growth modulating factors in urticaria.

METHODS

Tissue sections from patients with different types of urticaria and healthy controls were studied for the immunohistochemical expression of known mast cell growth factors (stem cell factor, SCF; nerve growth factor, NGF), of the inhibitory granulocyte-macrophage colony-stimulating factor (GM-CSF), and of the corresponding receptors, using the alkaline phosphatase-antialkaline phosphatase technique.

RESULTS

Compared to skin of normal controls, staining for SCF, but not for NGF and GM-CSF, was significantly decreased in epidermis, endothelium and perivascular cells in lesional and nonlesional skin of all urticarias. On separate analysis of urticaria subtypes, decreased expression reached significance only in delayed pressure urticaria. Expression of the p75NGF receptor (p75NGFR) was also significantly decreased on endothelium and on perivascular cells of lesional and nonlesional skin in all urticarias. On evaluation of serial sections, p75NGFR expression was also decreased on c-Kit positive dermal mast cells. In contrast, expression of the NGF receptor tyrosine kinase and of the SCF and GM-CSF receptors was unchanged.

CONCLUSIONS

These findings show that SCF and p75NGFR are selectively and systemically down-regulated in the skin of urticaria patients and may represent a negative feedback to increased mast cell reactivity and proliferation.

Monitoring serum concentrations of clomipramine and metabolites: fluorescence polarization immunoassay versus high performance liquid chromatography

This study compared fluorescence polarization immunoassay (FPIA) with a high performance liquid chromatographic (HPLC) method from the point of view of their applicability to therapeutic drug monitoring of patients treated with clomipramine alone. Blood was withdrawn from 20 depressed inpatients (54 +/- 14 years) under steady state conditions. The FPIA determined total tricyclic antidepressant (TCA) concentrations with day to day variability below 11%. The automated HPLC method separated clomipramine, N-desmethylclomipramine, 8-hydroxyclomipramine and 8-hydroxydesmethylclomipramine with interassay coefficients of variance below 12%. The concentrations measured by FPIA were similar to HPLC results. Total TCA concentrations measured by FPIA and the sum of clomipramine and desmethylclomipramine measured by HPLC correlated significantly (r = 0.780 and p < 0.01). However, 40% of individual FPIA determinations yielded results that differed by more than 50% from the HPLC concentrations. Changes in clinical rates were related only to TCA serum concentrations that had been analyzed by HPLC. It is concluded that the semiquantitative FPIA is unsuitable for therapeutic drug monitoring in patients under clomipramine treatment, whereas the differential analysis of clomipramine and metabolites by HPLC is informative and can be used to improve the antidepressant drug treatment.

[Esterase XX. Disc-electrophoretic investigations on the polymorphism of the esterases of the house mouse (author's transl)]

For the further clarification of the polymorphism of mouse-esterase and its hormonal control, which in part have not yet been fully comprehended, disc-electrophoretic analyses of eight organs were made, using a strain with the Tfm-mutation. In addition, quantitative assays of esterase activity as well as histochemical studies were performed. The individual organs are characterized by a specific banding pattern of esterase, which is essentially conditioned by the diverse activity of a limited number of bands. Partly these may be regarded as primary gene products, partly they seem to be secondary modifications. The few incidences of band-linkage justify the expectations, that further gene loci will be discovered. In four organs of Tfm-mutants a lower esterase activity was found than in the controls, which was especially distinct in the kidney. The behaviour of the testosterone-dependent bands in the kidneys of Tfm-mutants seems to indicate two different mechanisms of the effect of testosterone on these bands.

Day- and night-time contents of monoamines and their metabolites in the medial preoptic area of the rat hypothalamus

The present study was conducted to investigate whether monoamines and their metabolites in the medial preoptic area (mPOA) of the rat hypothalamus exhibit differences in their contents between day and night. We therefore sampled the mPOA from adult animals of either sex at the middle of the light or dark period, respectively, and analyzed the tissue by means of high performance liquid chromatography with electrochemical detection. We found that, in female animals at mid-night, dopamine and 3,4-dihydroxyphenyl acetic acid (DOPAC) was reduced to 43 and 30%, respectively, of daytime levels, while the norepinephrine content was doubled. No significant differences were observed in male animals. We also conducted immunohistochemistry of the catecholamine synthesizing enzymes, tyrosine hydroxylase (TH) and dopamine-beta-hydroxylase (DBH), in sections from perfusion-fixed male rats and showed that TH is present in neuronal perikarya and processes in the anteroventral periventricular region of the mPOA, while DBH was only seen in fibers and terminals. Our results of sex-specific and day time-dependent variations in dopamine and norepinephrine concentrations indicate that the two monoamines are candidate neurotransmitters that may transmit diurnal information to the mPOA.

[Plasmapheresis and immunopathogenetic aspects of toxic epidermal necrolysis]

Drug-induced toxic epidermal necrolysis (TEN) is a rare but frequently lethal disease of the skin and mucosa of unknown etiology. Toxic metabolic and immunologic products in the serum have been discussed as possible causes. For this reason we have performed plasmapheresis on these patients for many years. Results regarding survival and healing of the lesions are quite favorable, as exemplified with two patients described here who benefited from the procedure despite their old age. In order to gain insight into possible disease mechanisms that would explain the beneficial effect of plasmapheresis, we did immunohistochemical studies on these patients before and in one case after the procedure. In dermis and epidermis, there was a striking increase of macrophages and a relative increase of CD8-positive lymphocytes which might act as cytotoxic effector cells; these findings can be interpreted as the result of an immunological reaction. An increased staining of lesional epidermis with TNF alpha, as previously noted by other authors, should be interpreted with caution since necrotic cells are involved. On the basis of the clinical results, the pathogenetic considerations, and in view of the lack of specific treatment modalities, clinical studies concerning plasmapheresis for the treatment of toxic epidermal necrolysis are recommended, particularly since this procedure is widely available and generally well tolerated.