Human dermal mast cells contain and release tumor necrosis factor alpha, which induces endothelial leukocyte adhesion molecule 1

Differential reactivity of anti-E-selectin monoclonal antibodies in human gingival tissue

E-selectin is a cytokine-inducible endothelial glycoprotein which participates in the binding of leukocytes to vascular endothelium. Variable levels of expression of E-selectin have been reported in gingivitis and periodontitis, and two differing concepts of its significance have emerged: either gingival blood vessels express E-selectin constitutively, or are continuously activated by inflammatory mediators arising from the gingival environment. A range of monoclonal antibodies reacting with different epitopes of E-selectin are available commercially. The present study explored the possibility that the choice of antibody could affect estimation of the level of expression of E-selectin in vivo. Five monoclonal antibodies were used to investigate E-selectin expression in serial cryosections of human gingival tissue. While E-selectin-positive vascular endothelial cells were detected with all antibodies, the number of positively staining endothelial cells varied, with BBA1 > H4/18 = H18/7 = 4D10 > 1.2B6. The frequency of strong staining in tissue specimens was BBA1 > 4D10 > H4/18 = H18/7 > 1.2B6, while the frequency of weak staining showed the reverse trend. Additionally, with antibodies H18/7 and 1.2B6, 17 and 36% of the specimens were E-selectin negative. The occurrence of what appear to be false positives and false negatives confounds estimation of the level of E-selectin expression. Based on these findings, patterns of endothelial E-selectin expression in gingivitis and periodontitis should be re-evaluated.

Computer-assisted three-dimensional reconstruction of human dermal dendrocytes

We attempted to characterize the three-dimensional structure of dermal dendrocytes and to clarify the spatial relationships between dermal dendrocytes and mast cells, macrophages, and nerves. Normal human adult skin (breast, n = 2) was routinely processed for electron microscopy. Every other section (about 50 per data set) was collected at 80-nm intervals traversing about 8 microns of tissue. Grids showing the same cells were photographed by electron microscopy at a magnification of 4000x. Based on the 10-20 photographs per data set, cell outlines were digitized into the reconstruction program at appropriate layers and aligned. Thin, elongated cytoplasmic "dendrites" of dermal dendrocytes in two-dimensional micrographs proved to be thin, membrane-bound flaps in three-dimensional reconstruction. For dermal dendrocytes concentrated about superficial vessels (perivascular dendrocytes), the flaps enshrouded the vessel wall, and for dermal dendrocytes directly beneath the epidermis (subepidermal dendrocytes), these flaps were aligned parallel to the dermal-epidermal junction. The three-dimensional feature of dermal dendrocytes (perivascular and subepidermal) is quite similar to that of perivascular adventitial veil cells, suggesting ultrastructurally identified perivascular dendrocytes and veil cells must be identical cells. In conventional ultrathin sections, 20-40% of perivascular dendrocytes and occasional subepidermal dendrocytes were closely associated with mast cells. When viewed by computer-assisted three-dimensional reconstruction, membrane flaps of dermal dendrocytes consistently shrouded mast cell membranes for 50-90% of their perimeter; mast cells resembled a ball in a baseball glove (dermal dendrocytes). Occasional dermal dendrocytes surrounded non-myelinated nerves in the superficial dermis. Membrane flaps also enabled dermal dendrocytes to present extensive areas to the plasma membranes of adjacent monocyte/macrophages. These findings indicate that dermal dendrocytes are non-dendritic cells that are spatially related to mast cells, monocyte/macrophages, microvessels, and nerves by their membranous flaps. This suggests the need for further study of functional interactions between these cells.

Epidermal cell proliferation and terminal differentiation in skin organ culture after topical exposure to sodium dodecyl sulphate

Epidermal cell proliferation and differentiation were investigated in vitro after exposure to the anionic surfactant sodium dodecyl sulfate (SDS). Human skin organ cultures were exposed topically to various concentrations of SDS for 22 h, after which the irritant was removed. Cell proliferation was measured immunohistochemically by incorporation of bromodeoxyuridine (BrdU) into the DNA of cells during S-phase, while the expression of transglutaminase and involucrin were used as markers of differentiation. Cell proliferation was moderately increased at concentrations of SDS that did not affect the histomorphology (0.1% and 0.2% SDS). A marked increase of cell proliferation was observed 22 to 44 h after removal of SDS at a concentration (0.4%) that induced slight cellular damage. Exposure of human skin organ cultures to a toxic concentration of SDS 91.0% led to decreased cell proliferation. Transglutaminase and involucrin were expressed in the more basal layers of the epidermis after exposure to 0.4% or 1.0% SDS. Moreover, intra-epidermal sweat gland ducts were positive for transglutaminase at these irritant concentrations. These in vitro data demonstrate that SDS-induced alterations of epidermal cell kinetics, as described in vivo are at least partly due to local mechanisms and do not require the influx of infiltrate cells. However, we were unable to relate to altered cell kinetics to the release of interleukin-1 alpha or interleukin-6. Furthermore, supplementation of the culture medium with 12-hydroxyeicosantetraenoic acid did not affect epidermal cell proliferation. Rabbit skin cultures appeared more sensitive to SDS than human skin. At nontoxic doses, the irritant induced an increase of epidermal cell proliferation, similar to that observed in human skin discs.

Mast cells are potent regulators of endothelial cell adhesion molecule ICAM-1 and VCAM-1 expression

To investigate the possible role of mast cells (MC) in regulating leukocyte adhesion to vascular endothelial cells (EC), microvascular and macrovascular EC were exposed to activated MC or MC conditioned medium (MCCM). Expression of intercellular and vascular adhesion molecules (ICAM-1 and VCAM-1) on EC was monitored. Incubation of human dermal microvascular endothelial cells (HDMEC) and human umbilical vein endothelial cells (HUVEC) with activated MC or MCCM markedly increased ICAM-1 and VCAM-1 surface expression, noted as early as 4 hr. Maximal levels were observed at 16 hr followed by a general decline over 48 hr. A dose-dependent response was noted using incremental dilutions of MCCM or by varying the number of MC in coculture with EC. At a ratio as low as 1:1,000 of MC:EC, increased ICAM-1 was observed. The ICAM-1 upregulation by MCCM was > 90% neutralized by antibody to tumor necrosis factor alpha (TNF-alpha), suggesting that MC release of this cytokine contributes significantly to inducing EC adhesiveness. VCAM-1 expression enhanced by MCCM was partly neutralized (70%) by antibody to TNF-alpha; thus other substances released by MC may contribute to VCAM-1 expression. Northern blot analysis demonstrated MCCM upregulated ICAM-1 and VCAM-1 mRNA in both HDMEC and HUVEC. To evaluate the function of MCCM-enhanced EC adhesion molecules, T cells isolated from normal human donors were used in a cell adhesion assay. T-cell binding to EC was increased significantly after exposure of EC to MCCM, and inhibited by antibodies to ICAM-1 or VCAM-1. Intradermal injection of allergen in human atopic volunteers known to develop late-phase allergic reactions led to marked expression of both ICAM-1 and VCAM-1 at 6 hr, as demonstrated by immunohistochemistry. These studies indicate that MC play a critical role in regulating the expression of EC adhesion molecules, ICAM-1 and VCAM-1, and thus augment inflammatory responses by upregulating leukocyte binding.

Induced expression of mRNA for IL-5, IL-6, TNF-alpha, MIP-2 and IFN-gamma in immunologically activated rat peritoneal mast cells: inhibition by dexamethasone and cyclosporin A

We examined the capacity of purified rat peritoneal connective tissue-type mast cells (PMC) to express mRNA for several cytokines. Stimulation of PMC with anti-IgE for 4 hr induced the expression of mRNA encoding interleukin-5 (IL-5), IL-6, tumour necrosis factor-alpha (TNF-alpha), macrophage inflammatory protein-2 (MIP-2) and interferon-gamma (IFN-gamma). Unstimulated PMC expressed detectable mRNA for TNF-alpha but not for the other four cytokines. Incubation of PMC with cyclosporin A (CsA) or dexamethasone (DEX), each at 10(-6) M for 24 hr, significantly inhibited the induced expression of mRNA for each of the five cytokines, and also inhibited release of biologically active TNF-alpha. Throughout these experiments mRNA levels of the housekeeping gene G3PDH were not altered by stimulation with anti-IgE or incubation with CsA or DEX. We conclude that immunological activation of rat PMC induces gene expression of several cytokines and that expression of these genes can be inhibited by immunosuppressive drugs.

Bovine serum albumin preparations enhance in vitro production of tumor necrosis factor alpha by murine macrophages

Tumor necrosis factor alpha (TNF-alpha) is most commonly produced by macrophages stimulated by lipopolysaccharide (LPS). The present study shows that BSA in place of FBS in RPMI 1640 medium accelerated the rate of LPS-induced TNF-alpha production by resident peritoneal macrophages from BALB/c mice when compared to LPS in serum free medium. Using 10 or 100 ng LPS/ml and 100 U IFN-gamma/ml in RPMI 1640 medium plus 0.5% BSA, both cytoplasmic TNF-alpha mRNA and TNF-alpha precursor and extracellular TNF-alpha production by mouse macrophages were increased when compared to stimulation by LPS plus IFN-gamma in medium without BSA and FBS. The level of TNF-alpha produced was shown to be related to the BSA concentration. Medium containing BSA but no LPS also stimulated macrophages to produce TNF-alpha, but BSA's TNF-alpha inducing activity varied among different lots and was not blocked by polyclonal antibody to BSA. This effect appeared to be associated with the presence of immunoglobulin in BSA products. Confirmation that BSA activity was not due to LPS contamination was achieved by testing macrophages from LPS-nonresponder C3H/HeJ mice, as well as testing TNF-alpha induction in the presence of polymyxin B (10 micrograms/ml), an LPS inhibitor.

Mouse mast cell cytokine production: rôle in cutaneous inflammatory and immunological responses

The rôle of mast cells in cutaneous physiology and pathology has long been a subject of intense speculation and great clinical interest. In this brief review, which is focused primarily on murine systems, we outline certain important aspects of the biology of the mast cell, including their ability to produce a variety of cytokines, describe the development of a model system (the "mast cell knock-in mouse") for studying the roles of cutaneous mast cells in biological responses in vivo, and illustrate a few examples of how this approach has been used to investigate the contributions of mast cells and their cytokines to cutaneous inflammatory or immune responses.

Cytokine secretion by human mast cells

Mast cells have been traditionally viewed as effector cells of immediate-type hypersensitivity reactions. Besides this, mast cell activation and degranulation have been associated with various biologically and clinically important functions. Results of the past few years suggest that mast cells are involved in the development of late-phase reactions and influence other chronic inflammatory responses through the generation and secretion of various multipotential cytokines.

Relationship between mast cell degranulation and inflammation in the oral cavity

Mast cells are granule-containing secretory cells which are distributed preferentially about the microvascular bed in oral mucosa. This work examined the contribution of mast cell mediators to inflammation in the oral cavity. Mast cells in oral tissues expressed the serine proteases, tryptase and chymase, with a minor subpopulation being chymase-negative. Mast cells contained the cytokine tumour necrosis factor-alpha (TNF) in their granules. Degranulation of mast cells was a consistent feature of inflammatory lesions (lichen planus, gingivitis, pulpitis, periapical inflammation). In lichen planus, intracellular stores of TNF were depleted, and expression of mRNA for TNF was upregulated, indicating ongoing production and release of the cytokine. The density of mast cells in tissue compartments was related to the level of expression of E-selectin, an endothelial adhesion molecule which is known to be induced in skin by TNF derived from degranulating mast cells. Further attention should be directed toward the role of mast cell products, particularly TNF, in inflammation in the oral cavity.

Distribution, activation and tryptase/chymase phenotype of mast cells in the rheumatoid lesion

OBJECTIVE

To determine the distribution, activation, and tryptase/chymase phenotype of mast cells (MCs) in the rheumatoid lesion.

METHODS

MC tryptase and chymase were studied by immunohistochemistry using monoclonal antibodies and examination by brightfield, interference, and fluorescent microscopy. Thirty four specimens of cartilage-pannus junction and 26 specimens of rheumatoid synovium, all derived from knee surgery, were examined.

RESULTS

MCs were identified in all specimens examined, but their distribution and local concentrations varied, both within and between specimens. As a proportion of total synovial cells, there were more MCs in fibrous synovial tissues than in those with active inflammatory cell infiltrations; MCs usually showed a peripheral distribution around lymphocytic/mononuclear cell infiltrations. Most cartilage-pannus specimens demonstrated local concentrations of MCs at, or close to, sites of cartilage erosion, a significant proportion of which showed extracellular tryptase indicative of MC degranulation. MC degranulation was often associated with localised oedema and disruption of the stromal matrix. Two MC phenotypes were identified: one population contained tryptase alone (MCT) whilst another contained both tryptase and chymase (MCTC). The ratio MCT:MCTC approximated 8:1.

CONCLUSIONS

This histological study demonstrated that local concentrations of MCs and their activation/degranulation are commonly observed in the rheumatoid lesion, and especially at sites of cartilage erosion. Such observations add weight to the concept that MCs contribute to the processes of inflammation, matrix degradation and tissue remodelling.

Ultraviolet B irradiation of skin induces mast cell degranulation and release of tumour necrosis factor-alpha

In the 'sunburn' response in skin, dermal blood vessels are activated and traffic of dendritic Langerhans' cells altered. While these changes have been attributed to the cytokine TNF-alpha, the source of this acutely released TNF has not been identified. This report demonstrates that the 'sunburn' response, both in vivo and in vitro, is accompanied by rapid degranulation of cutaneous mast cells, with consequential release of intracellular stores of TNF. Epidermal keratinocytes were only minor contributors to local TNF production. Expression of the TNF-inducible CD62E (E-selectin/ELAM-1) and CD54 adhesion molecules on cutaneous endothelium occurred 2 h following mast cell degranulation, and this event was sensitive to blockade of mast cells with disodium cromoglycate. These results indicate that TNF release in skin in the acute sunburn response can largely be attributed to mast cells.

TNF alpha is localized to nasal mucosal mast cells and is released in acute allergic rhinitis

Allergic mucosal inflammation is characterized by tissue infiltration with eosinophils, and associated activation of mast cells and T lymphocytes. Tumour necrosis factor (TNF) alpha/cachectin is a candidate cytokine relevant to the pathogenesis of these events through its capacity to upregulate the expression of endothelial cell adhesion molecules, mediate granulocyte chemoattraction, and activate eosinophils, mast cells and T cells. To investigate the presence and localization of TNF alpha in the nasal mucosa in allergic rhinitis, nasal biopsies from perennial rhinitic (n = 13) and non-rhinitic volunteers (n = 11) were embedded in glycol methacrylate and immunostained with a monoclonal antibody directed against TNF alpha, and adjacent 2 microns sections stained for tryptase, CD3 and eosinophil cationic protein. This identified positive immunostaining for TNF alpha in the submucosa of both the rhinitic and normal subjects (median cell counts 13 and 23 cells/mm2 respectively, P = 0.24) with cellular localization to mast cells but not to T-lymphocytes or eosinophils. In a subsequent study of seven atopic subjects, nasal allergen challenge produced increases in lavage levels of histamine and albumin, which was associated with significant release of TNF alpha as early as 2 min post-allergen when compared with the saline control day (P = 0.05). This difference was also apparent when studying the area under the curve both at 30 and 60 min post-challenge t-test (P = 0.015 and 0.02 respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

IL-4 enhances IL-3 and IL-8 gene expression in a human leukemic mast cell line

We examined the capacity of interleukin (IL)-4 to induce or enhance the expression of certain cytokines in resting and activated cells of the HMC-1 human leukemic mast cell line. The HMC-1 mast cells were cultured with or without recombinant human IL-4 and then activated with the calcium ionophore ionomycin. Stimulation of non-IL-4-treated cells with ionomycin (10 microM) for periods of 30 min to 8 hr induced expression of mRNA encoding IL-3, IL-4 and IL-8 but was without effect on levels of mRNA for tumour necrosis factor (TNF)-alpha or beta-actin. Culture of the cells with IL-4 (100 ng/ml) for 24 hr led to a small increase in resting levels of mRNA for IL-3 and IL-8 but not for IL-4, TNF-alpha or beta-actin. More notably, the IL-4 treatment produced a pronounced elevation of mRNA for IL-3 and IL-8 when the cells were subsequently activated with ionomycin. The IL-4 treatment produced a negligible effect on IL-4 mRNA, and no effect on TNF-alpha or beta-actin mRNA levels in ionomycin-activated cells. Quantitation of cDNA by competitive polymerase chain reaction (PCR) revealed that the IL-4 treatment produced a sixfold increase in ionomycin-induced levels of cellular IL-3 mRNA, a fourfold increase in induced IL-8 mRNA and less than a twofold increase in induced IL-4 mRNA. The IL-4 treatment led to a 15- to 20-fold increase in ionomycin-induced secretion of IL-3 product and a doubling of induced IL-8 product. These effects of IL-4 were not associated with increased mast cell numbers. We conclude that IL-4 alone is a weak activator of IL-3 and IL-8 gene expression in mast cells, but is able to enhance activation signals in stimulated mast cells leading to transcription and secretion of these two cytokines.

Cis-urocanic acid synergizes with histamine for increased PGE2 production by human keratinocytes: link to indomethacin-inhibitable UVB-induced immunosuppression

There is considerable evidence that suppression of the immune system by UVB (280-320 nm UV) irradiation is initiated by UVB-dependent isomerization of a specific skin photoreceptor, urocanic acid (UCA), from the trans to the cis form. Previous studies have confirmed that cis-UCA administration to mice 3-5 days prior to hapten sensitization at a distant site, suppresses the contact hypersensitivity (CHS) response upon challenge. This study demonstrates in mice that cis-UCA, like UVB, suppresses CHS to trinitrochlorobenzene by a mechanism partly dependent on prostanoid production. In vitro experimentation showed that human keratinocytes, isolated from neonatal foreskin, increased prostaglandin E2 (PGE2) production in response to histamine but not UCA alone. However, cis-UCA synergized with histamine for increased PGE2 production by keratinocytes. Cis-urocanic acid also increased the sensitivity of keratinocytes for PGE2 production in response to histamine. Prostaglandin E2 from keratinocytes exposed to cis-UCA and histamine may contribute directly, or indirectly, to the regulation of CHS responses by UVB irradiation.

Interleukin 8 and mast cell-generated tumor necrosis factor-alpha in neutrophil recruitment

In the reverse passive Arthus reaction in mouse skin and immune injury of mouse dermal basement membrane, neutrophil (PMN) infiltration in mast cell deficient WBB6F1-W/Wv (W/Wv) mice was only 40% of that in WBB6F1-(+)/+ (+/+) mice that had a normal mast cell repertoire. An anti-tumor necrosis factor-alpha (TNF-alpha) monoclonal antibody (mAb) decreased PMN infiltration by 35-80% in +/+ but not W/Wv mice. In addition, an anti-human interleukin-8 (IL-8) MAb, DM/C7, inhibited PMN infiltration of the skin induced by either intradermal administration of recombinant human IL-1 beta or immune complex deposition. In both models of immune complex injury, DM/C7 reduced PMN infiltration by 40-60% in +/+ mice but not W/Wv mice. PMN infiltration and the sensitivity of this infiltration to anti-TNF-alpha or DM/C7 MAb in W/Wv mice whose mast cell population had been restored was indistinguishable from the influx observed in +/+ mice. These data suggest that TNF-alpha, IL-8, and mast cells play a fundamental role in PMN recruitment following immune complex injury.

Heat shock protein expression in oral lichen planus

To assess the potential role of heat shock protein (HSP) in the pathogenesis of oral lichen planus (OLP), sections of OLP, normal oral mucosa, non-specific oral ulceration (NSOU) and dysplastic OLP were assessed for HSP expression using avidin-biotin complex immunohistochemistry with an anti-HSP 70 polyclonal antibody. There were statistically significant differences in both the vertical and horizontal staining distribution when other groups were compared with the OLP group (p < 0.01). Using microdensitometry, the mean staining intensity in OLP, dysplastic OLP and NSOU was elevated in comparison with normal oral mucosa (p < 0.001). In a standard tritiated thymidine uptake assay, lymphocytes extracted from nine OLP lesions demonstrated significant proliferation when stimulated with purified protein derivative (PPD), of which HSP is a major constituent, with stimulation indices ranging from 2 to 132. These results are consistent with the hypothesis that, in OLP patients, diverse exogenous agents may cause upregulated expression of HSP by oral mucosal keratinocytes. A reaction of cytotoxic T lymphocytes to these activated keratinocytes may then result in the tissue destruction which is characteristic of OLP lesions.

Mast cell proteinases and cytokines in skin inflammation

The role of mast cells in provoking immediate-type hypersensitivity reactions is well established, but their involvement in chronic inflammation and immune reactions is not so clear. Mast cells synthesize and secrete large amounts of active proteinases, including tryptase, chymase, carboxypeptidase and cathepsin G, which can rapidly process numerous biologically active peptides and proteins or their precursors. Furthermore, mast cells are able to produce a variety of cytokines such as interleukin-4 (IL-4), IL-5, IL-6, tumour necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) which are known to be intensively involved in modulating and directing inflammatory responses in the skin. In this review, the role of mast cell proteinases and cytokines in skin inflammation is discussed.

Comparative cytokine release from human monocytes, monocyte-derived immature mast cells, and a human mast cell line (HMC-1)

To obtain further information regarding the role of cytokines during mast cell differentiation, we have investigated changes of cytokine secretion in mast cells developing from the human peripheral blood monocytic cell fraction during culture with fibroblast-derived conditioned media. The influence of stem cell factor and an antibody to the respective receptor in our culture system was studied as well. Interleukin (IL)-1 alpha, IL-1 beta, IL-6, and tumor necrosis factor (TNF)alpha were spontaneously secreted by cultured cells at day 1 and decreased markedly by day 14. Similar changes occurred also during culture with stem cell factor and were partially abrogated by an anti-receptor antibody. IL-8 was secreted at a high level throughout the culture, whereas no spontaneous secretion of IL-2, IL-3, IL-4, and IL-7 was measured at all. Upon stimulation with phorbol myristate acetate and A23187, cultured cells showed substantially more release of IL-3 and TNF-alpha after 14 d of culture, compared to peripheral blood monocytic cells. Preformed TNF-alpha was found in one of three monocytic cell preparations from peripheral blood, but not in monocytic cell-derived mast cells. During mast cell differentiation, cytokines from monocytic cells are therefore downregulated while the cells assume a pattern typically found in mast cells.

Mast cells are one major source of interleukin-4 in atopic dermatitis

Several reports have shown the presence of T-helper lymphocytes with Th2 characteristics in the skin lesions of atopic dermatitis (AD). However, Th2 cells themselves require an exogenous pulse of IL-4 to initiate their differentiation and synthesis of IL-4. As mast cells have recently been shown to contain IL-4, this finding prompted us to investigate IL-4 in mast cells of AD lesions, to determine if they might provide the IL-4 pulse needed by the Th2 cells. In this study, we measured IL-4 immunoreactivity in mast cells of non-lesional and lesional skin sections from 20 patients with AD. Ten patients with nummular eczema (NE) without any atopic features or background, and five healthy subjects, served as the control groups. Mast cells were first identified using an enzyme--histochemical staining method for tryptase. Subsequently, the sections were photographed, the tryptase stain was removed, and IL-4 was demonstrated with a polyclonal antibody. The sections were photographed again, and the percentage of IL-4 positive mast cells was calculated. The percentage of mast cells exhibiting IL-4 immunoreactivity in the upper dermis in lesional vs. non-lesional skin was 66 +/- 18% vs. 37 +/- 18% in AD (P < 0.0001, paired t-test), but only 46 +/- 19% vs. 31 +/- 22% in NE. In the skin of healthy controls, only 23 +/- 25% of the mast cells were positive for IL-4. In addition, a significant difference was found between lesional skin of AD vs. NE patients (P < 0.008, unpaired t-test).(ABSTRACT TRUNCATED AT 250 WORDS)

Ultrastructural immunogold localization of tumor necrosis factor-alpha to the cytoplasmic granules of rat peritoneal mast cells with rapid microwave fixation

Tumor necrosis factor-alpha (TNF-alpha) is a multifunctional, proinflammatory cytokine, which can be produced by mast cells and several other cell types. We used a newly developed microwave energy-assisted aldehyde fixation method to prepare purified rat peritoneal mast cells for the postembedding immunogold ultrastructural localization of TNF-alpha. These fixation methods were superior to chemical fixation alone in preserving both the ultrastructural morphology and immunoreactive TNF-alpha in rat mast cells. The percent of TNF-alpha-positive mast cells in samples prepared with microwave-assisted fixation in low (84%) and standard (81%) glutaraldehyde concentrations exceeded that for low (56%) and standard (15%) glutaraldehyde concentrations without the assistance of microwave energy. TNF-alpha was identified in the large storage granules of rat mast cells. The percent of positive granules in microwave-assisted standard (44%) and low (40%) glutaraldehyde samples was considerably higher than the percent of positive granules in standard (5%) and low (10%) glutaraldehyde-fixed samples without microwave assistance. This location of TNF-alpha in rat peritoneal mast cells suggests that this cytokine can use the regulated secretory route(s) for release from appropriately stimulated rat mast cells into the microenvironment.

Drug-induced expression of intercellular adhesion molecule-1 on lesional keratinocytes in fixed drug eruption

The mechanism(s) and the factor(s) that contribute to preferential localization of fixed drug eruption (FDE) lesions to certain skin sites remain speculative. Previous studies suggested that populations of T cells residing in the lesional epidermis may be involved in selective destruction of the epidermis in FDE. In this study, to define the earliest cellular and molecular events with potential relevance to activation of the epidermal T cells, expression of adhesion molecules on keratinocytes (KC) and vascular endothelium was examined sequentially in the lesional skin of FDE patients after challenge with the causative drug. Rapid and intense intercellular adhesion molecule-1 (ICAM-1) expression was induced on the vascular endothelium and KC as early as 1.5 hours after challenge, at which time E-selectin and vascular cell adhesion molecule-1 (VCAM-1) were not up-regulated. In vitro studies using skin organ culture showed that the lesional KC and endothelium responded more rapidly and intensely to express ICAM-1 to tumor necrosis factor-alpha or interferon-gamma compared with those in the nonlesional skin. Surprisingly, such selective induction of KC ICAM-1 restricted to the lesional skin was also observed after exposure to the causative drug alone in skin organ culture. Pretreatment of the lesional skin with anti-tumor necrosis factor completely abrogated in vitro induction of KC ICAM-1 expression by the drug. Drug-induced, TNF-alpha-dependent KC ICAM-1 expression in the lesional skin suggests that induction of ICAM-1 expression by the lesional KC after ingestion of the drug would probably provide a localized initiating stimulus for activation of the disease-associated epidermal T cells.

TNF alpha-induced activation of eosinophil oxidative metabolism and morphology--comparison with IL-5

Human dermal mast cells are capable of releasing cytokines, particularly preformed TNF alpha, upon appropriate stimulation. Mast cell activation in vivo was shown to be associated with an influx and activation of inflammatory cells, initially PMN (polymorphonuclear neutrophilic granulocytes) then eosinophils. In order to learn more about the mechanisms by which TNF alpha is capable of activating eosinophils, in the present study the effect of TNF alpha on morphology and function of highly purified normal eosinophils (> or = 95%) was examined. As estimated by transmission and scanning electron microscopy, TNF alpha-stimulated eosinophils appeared to be strictly adherent and flattened exhibiting a characteristic "hemispheric" shape. TNF alpha induced a dose-dependent, long-lasting production of reactive oxygen species as measured by lucigenin-dependent chemiluminescence (CL), even at a concentration of 0.001 U/ml. The maximal response upon stimulation with TNF alpha, however, was significantly lower than optimal effects induced by IL-5. TNF alpha-induced responses were completely inhibited by cytochalasin B and staurosporin, and partially blocked by pertussis toxin. Separation of eosinophils by discontinuous density gradients revealed the existence of at least two hypodense eosinophil populations with a distinct susceptibility to stimulation with TNF alpha. Based on functional assay systems, in contrast to a significant extracellular, only a small intracellular H2O2 production was detected. Accordingly, H2O2 production, detected by an ultrastructural technique, was observed only on the outer surface of the plasma membrane in the contact zones in between adjacent cells. Extracellular as well as intracellular production of H2O2 was completely inhibited by cytochalasin B. TNF alpha-induced activation of eosinophils is most probably mediated by binding to the 55 kD and the 75 kD TNF-receptor since both receptor molecules could be detected by FACS analysis and immune electron microscopy using receptor-specific antibodies. However, in contrast to its effect on eosinophil oxidative response, TNF alpha did not induce the release of significant concentrations of eosinophil cationic protein or eosinophil peroxidase in supernatants of cytokine-stimulated eosinophils, as detected by functional as well as immunological assay systems. These results clearly indicate that TNF alpha represents a potent eosinophil-activating cytokine which may be of relevance in the allergic inflammatory response.

Mechanisms of the human allergic response. Clinical implications

During the past decade, there have been enormous strides made in our understanding of the mechanisms underlying the human allergic response. In particular, interleukin-4 and interleukin-5 play a critical role in this process. This article details the understanding of the mechanisms underlying the regulation of allergic response, which is critical to the development of new treatment of allergic diseases.

Permeability barrier disruption alters the localization and expression of TNF alpha/protein in the epidermis

Previous studies have shown that (1) epidermal TNF alpha mRNA levels are increased following acute disruption of the cutaneous permeability barrier; (2) this increase is maximal at 1 h and decreases to control levels by 8 h; and (3) in essential fatty acid-deficient (EFAD) mice, a chronic model of barrier perturbation, TNF alpha mRNA levels are also elevated several-fold over controls. In the present study we determined, using immunocytochemical procedures, epidermal TNF alpha protein levels following either acute of chronic barrier disruption and the localization of any increase. Frozen, paraffin and Antibed sections of skin were incubated with polyclonal anti-mouse TNF alpha antisera and detection was accomplished by either immunoperoxidase or fluorescence procedures. We found that (1) TNF alpha-immunoreactive protein was present in normal mouse epidermis, and was primarily localized to the upper nucleated layers where it displayed a diffuse cytosolic pattern; (2) acute disruption of the barrier with acetone or tape-stripping resulted in TNF alpha staining that was more intense throughout all of the nucleated epidermal cell layers in comparison with normal epidermis; (3) the increase in TNF alpha staining occurred as early as 2 h after barrier disruption; and (4) increased TNF alpha staining was also observed in the stratum corneum of EFAD mice. These results indicate that epidermal TNF alpha protein levels increase after both acute and chronic barrier disruption, and are consistent with the hypothesis that TNF alpha may signal and/or coordinate portions of the cutaneous response to barrier disruption.

Role of mast cells in early epithelial target cell injury in experimental acute graft-versus-host disease

The skin is a major target organ for graft-versus-host disease (GVHD), the principal complication of allogeneic bone marrow transplantation. The purpose of the present study was to test whether mast cell degranulation might be related to early target cell injury in the development of acute GVHD. We employed two irradiated murine strain combinations, one in which disease was mediated by CD4+ effector T cells (B10.D2-->DBA/2), and the other by CD8+ effector T cells (B10.BR-->CBA). As compared to controls, both models exhibited mast cell degranulation of differing extents and patterns, as well as dyskeratosis in the epidermis before the influx of effector lymphocytes. These results suggested that factors produced and released by degranulated dermal mast cells might contribute to early target cell injury. Accordingly, the possible role of tumor necrosis factor (TNF)-alpha, a cytokine recently discovered in mast cell granules, was investigated by the injection of anti-TNF-alpha antibody during the course of disease mediated by either CD4+ or CD8+ T cells. Although overall survival of recipients undergoing CD4+ T-cell-mediated GVHD was only slightly improved and the extent of mast cell degranulation was not affected by anti-TNF-alpha antibody treatment, the skin exhibited a significant diminution in the number of dyskeratotic cells/linear mm at 3-4 weeks post-transplantation. In contrast, anti-TNF-alpha antibody failed to enhance survival or reduce the number of dyskeratotic cells in the skin during CD8+ T-cell-mediated disease. Finally, to determine whether CD8+ T-cell-mediated GVHD was at all dependent upon mast cell involvement, the C3H.SW-->B6WWv strain combination was utilized, in which recipients were genetically deficient in mast cells. Onset of GVHD was significantly delayed in B6WWv mice and was clearly correlated to the appearance and increase of de novo mast cells at later time points.

The immunocytochemical localization of tumour necrosis factor and leukotriene in the rat heart and lung during endotoxin shock

After the intravenous administration of lipopolysaccharide at a dose of 3.0 mg/100 g to rats, immunoreactive sites for tumour necrosis factor (TNF) and peptide leukotrienes (LTs) were examined in the heart and lung. Immunoreaction for TNF is preferentially localized on the apical endothelial cell surface of the vessels and in lysosomes of inflammatory and interstitial cells. Lysosomes of cardiac muscle cells which undergo degeneration are also reactive. Peptide LTs in inflammatory cells give almost the same reactions as those for TNF. However, the production of peptide LTs occurs uniquely in cardiac muscle cells in the media of the pulmonary vein, although lysosomes of intracardiac muscle cells which undergo degeneration do not show immunoreactivity. These results suggest that the degeneration of cardiac muscle cells may be induced not only by endogenous TNF but also by peptide LTs which are produced in muscle cells of the venous media and are transported to the myocardium via the coronary circulation.

Bronchial biopsy evidence for leukocyte infiltration and upregulation of leukocyte-endothelial cell adhesion molecules 6 hours after local allergen challenge of sensitized asthmatic airways

We have examined the mucosal changes occurring in bronchial biopsies from six atopic asthmatics 5-6 h after local endobronchial allergen challenge and compared them with biopsies from saline-challenged segments from the same subjects at the same time point. All the subjects developed localized bronchoconstriction in the allergen-challenged segment and had a decrease in forced expiratory volume in 1 s (FEV1) (P < 0.01) and a decrease in their methacholine provocative concentration of agonist required to reduce FEV1 from baseline by 20% (P < 0.05) 24 h postchallenge. At 6 h we observed an increase in neutrophils (P = 0.03), eosinophils (P = 0.025), mast cells (P = 0.03), and CD3+ lymphocytes (P = 0.025), but not in CD4+ or CD8+ lymphocyte counts. We also detected an increase in endothelial intercellular adhesion molecule type 1 (P < 0.05) and E-selectin (P < 0.005), but not vascular cell adhesion molecule type 1 expression with a correlative increase in submucosal and epithelial LFA+ leucocytes (P < 0.01). Thus, in sensitized asthmatics, local endobronchial allergen instillation leads to an increased inflammatory cell infiltrate of the airway mucosa that involves upregulation of specific adhesion molecules expressed on the microvasculature.

The skin as an immune organ

As a protective interface between internal organs and the environment, the skin encounters a host of toxins, pathogenic organisms, and physical stresses. To combat these attacks on the cutaneous microenvironment, the skin functions as more than a physical barrier: it is an active immune organ. Immune responses in the skin involve an armamentarium of immune-competent cells and soluble biologic response modifiers including cytokines. Traversed by a network of lymphatic and blood vessels, the dermis contains most of the lymphocytes in the skin, other migrant leukocytes, mast cells, and tissue macrophages. Although the epidermis has no direct access to the blood or lymphatic circulation, it is equipped with immune-competent cells: Langerhans cells, the macrophage-like antigen-presenting cells of the epidermis; keratinocytes, epithelial cells with immune properties; dendritic epidermal T lymphocytes, resident cells that may serve as a primitive T-cell immune surveillance system; epidermotropic lymphocytes, migrants from vessels in the dermis; and melanocytes, epidermal pigment cells with immune properties. Although the components of the epidermis and dermis work in concert to execute immune responses in the skin, for purposes of this review, we focus on the cells and cytokines of the epidermal immunologic unit, the frontline of immune protection against environmental toxins and microbes.

Adhesion molecule expression in chronic inflammatory periodontal disease tissue

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

Atopic dermatitis: recent trends in pathogenesis and therapy

Emerging concepts in the areas related to the pathogenesis and treatment of atopic dermatitis are reviewed. In particular, recent findings have revealed several key steps in the maintenance of a vicious circle of spongiotic dermatitis associated with elevated T-lymphocyte activation, hyperstimulatory Langerhans cells, defective cell-mediated immunity, and B-cell IgE overproduction. The discovery of specific IgE-binding structures on Langerhans cells provides a mechanism for Langerhans cells to capture and present IgE-targeted allergens to allergen-specific T cells. Furthermore, certain microbial allergens that tend to preferentially elicit IgE-type responses also elicit a T-cell response dominated by the IgE-inducing lymphokine interleukin 4. Repeated stimulation by activated Langerhans cells appears to induce just such a response. Abnormal biochemical responsiveness and mediator release by AD monocytes, mast cells, and eosinophils also participate in the sustainment or initiation of such a vicious circle, and contribute directly to the dermatitis as well. Developments in the areas of neuropeptides, genetics, microbial superantigens, and cytokine networks in the skin also appear to have promise in providing a rational link between immune defects and the inflammatory events in AD. Conventional therapy remains the mainstay of atopic dermatitis management; however, new therapies based upon the above concepts are being tested in clinical trials. Although the difficulty of objectively grading AD lesional activity and the high placebo response of AD patients hampers the interpretation of many reports, several types of approaches are coming into focus. The effectiveness of cyclosporin A, which targets T-cell activation and antigen presentation, indicates that additional agents with such activity should be effective, and verifies the criticality of these cells in AD pathogenesis. Therapy with biologic response modifiers, such as interferon gamma or thymopentin, is oriented toward normalization of imbalanced immune responsiveness, rather than direct suppression of the immune system. The mechanism of action of and toxicities of Chinese herbal mixtures require further investigation, but may reveal hitherto unconsidered avenues. Other recent therapeutic trials have focused on reduction of trigger factors, such as house dust mite exposure, foods, and the abnormal epidermal lipid barrier to irritation.

Mast cells modulate acute ozone-induced inflammation of the murine lung

We hypothesized that mast cells modulate lung inflammation that develops after acute ozone (O3) exposure. Two tests were done: (1) genetically mast-cell-deficient (WBB6F1-W/Wv, WCB6F1-SI/SId) and bone-marrow-transplanted W/Wv mice were exposed to O3 or filtered air, and the inflammatory responses were compared with those of mast-cell-sufficient congenic mice (WBB6F1-(+)/+, WCB6F1-(+)/+); (2) genetically O3-susceptible C57BL/6J mice were treated pharmacologically with putative mast-cell modulators or vehicle, and the O3-induced inflammatory responses were compared. Mice were exposed to 1.75 ppm O3 or air for 3 h, and lung inflammation was assessed by bronchoalveolar lavage (BAL) 6 and 24 h after exposure. Relative to O3-exposed W/Wv and SI/SId mice, the mean numbers of lavageable polymorphonuclear leukocytes (PMNs) and total BAL protein concentration (a marker of permeability) were significantly greater in the respective O3-exposed normal congenic +/+ mice (p < 0.05). Mast cells were reconstituted in W/Wv mice by transplantation of bone marrow cells from congenic +/+ mice, and O3-induced lung inflammation was assessed in the mast-cell-replete W/Wv mice. After O3 exposure, the changes in lavageable PMNs and total protein of mast-cell-replete W/Wv mice were not different from age-matched normal +/+ control mice, and they were significantly greater than those of sham-transplanted W/Wv mice (p < 0.05). Genetically susceptible C57BL/6J mice were pretreated with a mast-cell stabilizer (nedocromil sodium), secretagogue (compound 48/80), or vehicle, and the mice were exposed to O3.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunopathogenesis of chronic inflammatory periodontal disease: cellular and molecular mechanisms

Recent studies of the cellular mechanisms involved in chronic inflammatory periodontal disease (CIPD) have contributed significantly to our understanding of the pathogenesis of the disease process. Functional studies have demonstrated polymorphonuclear neutrophil (PMN) chemotactic defects in some 70% of subjects with localized juvenile periodontitis while chemiluminescence data have suggested that peripheral blood PMNs from young subjects with adult periodontitis (AP) may be in a metabolically active state. Further studies have shown that stimulation of PMNs with a number of periodontopathic bacteria resulted in the production of an IL-1 inhibitor suggesting a possible regulatory role for PMNs in CIPD in addition to their established protective role. Most work on the immunoregulation of CIPD has, however, concentrated on T-cells. Recent limit dilution analysis has demonstrated the presence of periodontopathic bacteria-specific T cells in peripheral blood and the involvement and homing of these cells to the local lesions of CIPD is currently the focus of many studies. In animal studies, Actinobacillus actinomycetemcomitans (Aa)-specific T-cell clones home to the gingival tissues where they may exert a protective role. Homing and retention of lymphocytes to and in specific sites is dependent upon the expression of adhesion molecules. Recent data indicate however, that while there are increasing levels of ICAM-1, LECAM-1 and PECAM-1 expression with increasing degrees of inflammation, there are no differences between gingivitis and periodontitis lesions. Cytokine profiles may be related to the role of T-cell clones homing to the gingiva in CIPD.(ABSTRACT TRUNCATED AT 250 WORDS)

Mast cells are essential for the full development of silica-induced pulmonary inflammation: a study with mast cell-deficient mice

Silicosis provides a good model for chronic interstitial pulmonary inflammation. In order to clarify the role of mast cells in the development of interstitial lung diseases, silica suspension was transnasally administered to mast cell-deficient mice (WBB6F1-W/Wv) and their mast cell-intact littermates (WBB6F1(-)+/+) as well as to normal mice (C57BL/6). Histologic examinations and analyses of bronchoalveolar lavage fluid (BALF) components indicated that silica instillation induces less severe lung lesions in mast cell-deficient mice than in mast cell-intact mice. BALF neutrophilia was prominent in mast cell-intact mice, but mast cell-deficient mice developed significantly milder BALF neutrophilia. An increase in the number of lung mast cells was observed in mast cell-intact mice. To further prove the involvement of mast cells, bone marrow-derived cultured mast cells from +/+ mice were adoptively transferred to mast cell-deficient mice. These mast cell-reconstituted mice developed more severe pulmonary lesions than did the mast cell-deficient mice; the severity of the lesions was similar to that in mast cell-intact mice. In addition, BALF neutrophilia was elicited by mast cell reconstitution. A significant number of mast cells was found in the lungs of mast cell-reconstituted mice when silica was administered. These results suggest the involvement of mast cells in the development of silicosis and implicate interactions between mast cells and neutrophils in the pathogenesis of this disorder.

Localization of tumour necrosis factor-alpha (TNF-alpha) and its receptors in normal and psoriatic skin: epidermal cells express the 55-kD but not the 75-kD TNF receptor

The distribution of TNF-alpha, p55 TNF receptor (TNF-R) and p75 TNF-R in normal skin and uninvolved and lesional skin from psoriasis patients has been investigated, using specific mono- and polyclonal antibodies. In normal skin, and uninvolved and lesional skin from psoriasis patients, p55 TNF-R is associated with epidermal keratinocytes and a network of upper dermal dendritic cells. This suggests that the actions of TNF-alpha on epidermal cells in vivo are mediated by binding to the p55 TNF-R. In lesional psoriasis skin, there was staining of the parakeratotic stratum corneum and increased expression of p55 TNF-R in association with upper dermal blood vessels. Staining for p75 TNF-R in normal skin was restricted to eccrine sweat ducts and dermal dendritic cells, and was absent from the epidermis. In lesional psoriasis skin, there was staining for p75 TNF-R in association with upper dermal blood vessels and perivascular infiltrating cells. TNF-alpha in normal skin was predominantly localized to the basal cell layers of the epidermis, and was seen in association with eccrine ducts and sebaceous glands. In lesional psoriasis skin, and to a lesser extent in uninvolved psoriasis skin, TNF-alpha was distributed throughout the epidermis, and was also specifically localized to upper dermal blood vessels. Up-regulation of TNF-alpha, p55 TNF-R and p75 TNF-R on dermal blood vessels in psoriasis may play an important role in the pathogenesis of this condition by promoting cutaneous recruitment of inflammatory cells.

Modulation of adhesion molecule expression on endothelial cells during the late asthmatic reaction: role of macrophage-derived tumour necrosis factor-alpha

In a previous work we have demonstrated that in patients exhibiting a late allergic reaction (LAR), alveolar macrophages (AM) collected 18 h after bronchial allergen challenge produced high levels of IL-6 and tumour necrosis factor-alpha (TNF) which is known to up-regulate the endothelial cell expression of adhesion molecules participating in the development of the inflammatory reaction in bronchial asthma. For these reasons, we evaluated the effect of AM supernatants from asthmatic patients developing an LAR on intercellular adhesion molecule-1 (ICAM-1) and endothelial leucocyte adhesion molecule-1 (ELAM-1) expression by human endothelial cells. The expression of adhesion molecules was assessed by an ELISA method and compared with the effect of an optimal dose of human recombinant (hr) TNF. Results showed that AM supernatants, from challenged asthmatics developing an LAR, increased significantly the ICAM-1 and ELAM-1 expression on endothelial cells to a level similar to that obtained in the presence of hrTNF (500 U/ml) (P < 0.001 in both cases, respectively 90.4% and 75.2% of the level obtained with hrTNF). In contrast, AM supernatants from asthmatics at baseline or exhibiting, after challenge, a single early reaction had no significant effect on these parameters (P = NS in both cases, respectively 23.5% and 24.7% of the ICAM-1 expression, 22.7% and 15.3% of the ELAM-1 expression obtained with hrTNF). AM-derived TNF present in these supernatants was thought to play a key role in endothelial cell stimulation, since: (i) TNF concentration in AM supernatants correlated with its effect on ICAM-1 (r = 0.80, P < 10(-4)) and ELAM-1 expression (r = 0.88, P < 10(-5)); and (ii) a neutralizing anti-TNF antibody decreased their effect (68% and 80% respectively on ICAM-1 and ELAM-1 expression). Moreover, the role of IL-6 was excluded on the basis both of the hrIL-6 inefficiency to induce ICAM-1 and ELAM-1 synthesis, even in costimulation with hrTNF, and of anti-IL-6 antibody to neutralize the effect of AM supernatants. Our results suggest that, beside mast cells and lymphocytes, macrophages might participate in the induction of the local inflammatory reaction observed in bronchial asthma. During the LAR, cytokines and especially TNF are able, through an enhanced adhesion molecule expression on endothelial cells, to facilitate the bronchial cellular influx.

Expression of platelet-endothelial cell adhesion molecule-1 (PECAM-1) during melanoma-induced angiogenesis in vivo

Recent ultrastructural data indicate that tumor-induced angiogenesis involves polarized outgrowth of endothelial cells from established vessels into tumor parenchyma and interstitium. Efforts to define the cytoarchitecture of the angiogenic response and to ascertain molecular determinants of polarized endothelial migration have been impeded by lack of sensitive and specific immunologic markers for endothelium and vessel wall components. In this study, we utilized monoclonal antibody to platelet-endothelial cell adhesion molecule-1 (PECAM-1), a cell-cell adhesion molecule belonging to the immunoglobulin superfamily, to determine extent and patterns of angiogenesis in metastatic melanomas before (N = 7) and after (N = 3) induction of tumor-infiltrating lymphocyte responses provoked by administration of experimental melanoma vaccine. PECAM-1 proved to be a more reliable marker for angiogenesis than antibodies to von Willebrand Factor. Although both normal and tumor vessels exhibited prominent staining for PECAM-1, different patterns of endothelial reactivity were observed. Formation of new vessels was associated with i) PECAM-1 redistribution from a constitutive circumferential membrane pattern to a pattern restricted to cell-cell junctions; ii) formation of endothelial cords formed by cell-cell interactions; and iii) eventual development of open lumens. Vessels within inflamed (vaccine-treated) and non-inflamed melanomas did not differ with regard to patterns of PECAM-1 expression. Forming vessels of inflamed melanomas failed to express the cytokine-inducible activation marker, E-selectin. Although normal microvessels and reactive vessels of healing wounds demonstrated prominent staining for alpha 6 laminin receptor, vessels within melanomas showed apparently diminished expression.(ABSTRACT TRUNCATED AT 250 WORDS)

The immunocytochemical localization of tumour necrosis factor and leukotriene in the rat kidney after treatment with lipopolysaccharide

Abundant inflammatory cells such as polymorphonuclear leucocytes and macrophages accumulated and adhered to the endothelial surface of glomerular and intertubular veins and capillaries in rat kidneys after administration of bacterial lipopolysaccharide (LPS). There was also damage to both endothelial cells and proximal tubular cells, including intracytoplasmic oedema, and an increase in the number of lysosomes in the proximal tubular cells in the LPS-treated samples. Immunocytochemistry was used to demonstrate tumour necrosis factor (TNF) and leukotriene (LTR) in both LPS-treated and control samples. Immunoreactive LTR seen in the lysosomes of inflammatory cells attached to the endothelial cell surface may indicate the onset of endothelial cell damage. Positive immunoreactive TNF and LTR were seen on the endothelial cell surface only in the LPS-treated samples, indicating that TNF and LTR may enhance the adhesion of leucocytes to endothelium. Positive reactions of TNF and LTR in lysosomes of the mesangial cells suggest that lysosomes of such cells may be involved in the synthesis and storage of TNF and LTR. In addition to these reaction sites, lysosomes of proximal tubular cells were immunoreactive for LTR. These endogenous LTRs may be implicated in the degeneration of the proximal tubular cells.

Mast cell degranulation upregulates alpha 6 integrins on epidermal Langerhans cells

The expression of the alpha 6 beta 4 and alpha 6 beta 1 integrins on epidermal Langerhans cells (LC) before and after mast cell degranulation was studied in cultured human neonatal foreskin by immunohistochemistry. Twenty-four hours after addition of mast cell secretagogues, morphine sulfate, or substance P, solitary mid-epidermal cells showed staining for the integrin subunits alpha 6, beta 4, and beta 1. This expression was not observed in cultured control explants, and immunostained cells were confirmed to be non-epithelial, dendritic cells by immuno-electron microscopy. The identity of these cells as LC was further established by coincident staining for alpha 6 and CD1a using double immunofluorescence labeling. Addition of tumor necrosis factor-alpha (TNF alpha), the predominant cytokine in mast cell granules, also induced LC to express alpha 6 integrins. Furthermore, preincubation of skin organ cultures with anti-TNF alpha antibodies or the mast cell inhibitor cromolyn sodium abrogated the ability to induce alpha 6 integrins on LC consequent to experimental mast cell degranulation by substance P. These data implicate a role for mast cell-derived TNF alpha in the regulation of the integrins alpha 6 beta 4 and alpha 6 beta 1 on LC. These findings may have important implications relevant to mechanisms for spatial localization of LC within the cutaneous compartments during immune responses.