Quantitation of tryptase- and chymase-containing mast cells in cutaneous lichen planus.

The distribution and density of tryptase- and chymase-positive mast cells in lesional and non-lesional cutaneous lichen planus (LP) was analysed. For this, enzyme-histochemical staining techniques and morphometrical measurements were applied. In non-lesional LP skin, chymase-positive cells (TC mast cells) showed a distribution similar to that found in both non-lesional psoriatic skin and in normal skin. Tryptase-positive cells (reflecting both T and TC mast cells), however, were increased in number in the upper dermis of non-lesional LP skin. In lesional LP skin, there were fewer chymase-positive cells in the upper dermis, whereas there were more tryptase-positive cells. In the upper dermis, no differences in the number of tryptase containing cells were detected between lesional and nonlesional LP skin. In lesions of LP and psoriasis, tryptase-positive mast cells are increased but differ in their distribution in the papillary dermis. In psoriatic lesions, tryptase-positive cells are frequently observed in epidermal contact, a feature very rarely seen in LP lesions. The present results suggest that the increased numbers of T mast cells in the upper dermis of nonlesional LP skin may be involved in initiating the LP lesion. It seems unlikely that mast cells could be responsible for the epidermal basal cell damage, though T mast cells do participate in the general inflammatory reaction.     

Mast cell tryptase and chymase in developing and mature psoriatic lesions

The number and distribution of mast cells in nonlesional and lesional skin samples from 13 psoriatic patients were analyzed enzyme- and immunohistochemically. Mast cell tryptase was stained with the sensitive substrate Z-Gly-Pro-Arg-4-methoxy-2-naphthylamide, and chymase with Suc-Val-Pro-Phe-MNA and monoclonal B7 anti-chymase antibody. In addition, healthy-looking skin from 27 psoriatic patients was tape-stripped resulting in induction of the Köbner response in 9 patients. Sequential biopsies were taken before and after (7, 14 and 21 days) tape-stripping, and both tryptase and chymase were stained enzyme-histochemically. In nonlesional psoriatic skin, 70 ± 24% (mean ± SD) of the mast cells contained chymase enzyme activity, and 78 ± 18% chymase immunoreactivity. About 10% of the chymase-immunoreactive cells lacked chymase activity. In lesional psoriatic skin, tryptase-positive cells were increased in number throughout the dermis but especially beneath the epidermis. Chymase immunoreactivity paralleled the tryptase activity, whereas chymase activity was strongly diminished both in terms of mast cell numbers and in staining intensity in the papillary dermis. The apparent inactivation of chymase may be due to the action of the chymase inhibitors, ₁-antitrypsin and ₁-antichymotrypsin, localized immunohistochemically in mast cells of lesional and nonlesional psoriatic skin. In the developing psoriatic lesion, mast cells displaying chymase activity were already 27–38% decreased in number in the upper dermis on day 7 after tape-stripping, along with the first clinical signs of psoriasis. Earliest alterations in tryptase-positive cells were observed on day 14 as increased mast cell contacts with the epidermis combined with only a slight increase in mast cell numbers in the upper dermis. During the development of a psoriatic lesion, TC mast cells (tryptase⁺, chymase⁺) increase in number in the upper dermis, but chymase becomes inactive at an early stage. The abundant presence of active trypase but inactive chymase in the upper dermis may have a potential role in psoriasis since both of these enzymes can process several biologically active peptides and proteins.     

Decreased chymase activity is associated with increased levels of protease inhibitors in mast cells of psoriatic lesions

Mast cells contain large amounts of the powerful serine proteinases, tryptase and chymase, of which only chymase can be inactivated by serum protease inhibitors. In this study, 20 patients with psoriasis and a control group of 13 with atopic dermatitis were biopsied for lesional and non-lesional skin specimens. The presence of chymase inhibitor alpha 1-proteinase inhibitor (alpha 1-PI), alpha 1-antichymotrypsin (alpha 1-AC), alpha 2-macroglobulin (alpha 2-MG) and C1-esterase inhibitor (C1-Inh) immunoreactivity in mast cells was verified using the sequential double-staining method. Tryptase- and chymase-positive mast cells were stained enzyme-histochemically. Tryptase-positive mast cells were increased in number in the upper dermis of the psoriatic lesion compared with lesion-free psoriatic skin (308 +/- 109 vs. 100 +/- 29 cells/mm2, respectively, mean +/- SD, p < 0.0005, t-test) while the percentage of mast cells showing chymase activity was decreased (76.8 +/- 22.1% vs. 28.6 +/- 14.4%, p < 0.0005). These findings are consistent with our previous ones. In contrast to the decreased percentage of chymase-positive mast cells, a novel finding was that the percentages of alpha 1-AC+ (86.9 +/- 7.2% vs. 59.5 +/- 12.6%, p < 0.0005), alpha 1-PI+ (72.2 +/- 14.9% vs. 33.4 +/- 18.6%, p < 0.0005) and alpha 2-MG+ (16.8 +/- 7.0% vs. 6.2 +/- 3.5%, p < 0.002) mast cells were significantly higher in the psoriatic lesion with the exception of the percentage of C1-Inh+ mast cells (13.7 +/- 10.0% vs. 11.0 +/- 6.1%, p < 0.7). The localization of these inhibitors in mast cells is not a characteristic feature of psoriasis, since mast cells in atopic dermatitis skin also showed immunoreactivity though in slightly lower percentages. Previously, we have shown that MCTC (tryptase+, chymase+) mast cells increase in number in the psoriatic lesion but chymase becomes inactive. The results of this study show again the decreased chymase activity, which could be due to increased levels of its inhibitors (alpha 1-AC, alpha 1-PI and alpha 2-MG) in the same mast cells. Thus, active tryptase could promote inflammation but chymase seems not to be an important mediator in the pathomechanism of psoriasis.     

Quantitative analysis of tryptase- and chymase-containing mast cells in atopic dermatitis and nummular eczema

The distribution of mast cells (MCs) containing tryptase (T) and chymase (C) was studied in the non-lesional and lesional skin of 26 patients with atopic dertnatitis (AD) and 23 patients with non-atopic nummular eczema (NE). and in the skin of eight healthy controls. T and C activities were demonstrated enzymehistochemically using 2-Gly-Pro-Arg-MNA and Suc-Val-Pro-Phe-MNA as substrates, respectively. The T- and C-containing MCs were counted separately in the epidermis, in contact with the basement membrane. In the papillary dermis and in different dermal levels (0·2 mm each). Also, the C protein was determined immunohistochemically. T-positive MCs were similarly distributed in non-lesional and lesional skin of both AD and NE. The MC number was relatively high in the upper dermis (papillary dermis and levels I and I!) of non-lesional and lesional skin of AD. In the upper dermis of non-lesional AD and NE skin and in normal skin, about 50% of T-positive MCs displayed C activity, whereas the percentage in lesional AD and NE skin was only about 30%. hi this respect, the non-lesional and lesional samples differed significantly froLu each other in both dennatoses (in AD p = 0%005, in NEP = 0·002. Students' t-test). In all samples the MC number decreased in the deeper dermal levels, although numerous T-containing MCs were still counted in the deeper dermis (dermal levels IV-VII) of lesional AD and NE skiti. differing significantly from the MC number in normal skin (In ADp = 0·005. in NE p=0·041). In the deeper dermis. the percentage of MCs containing active C was about 70% in non-lesional and lesional AD and NE. and about 90% in normal healthy skin. However, in the upper dermis of non-lesional and lesional skin of both AD and NE. about H()% of all MCs contained the C protein, which differed significantly from the value of 100% in normal skin (p<0·5). In conclusion, the increased number of T-positive MCs in the upper dermis of non-lesional and lesional AD contributes to promoting inflammation. C apparently loses its activity in the upper dermis of lesional AD and especially in NE. Thus. Ihe enzyme partially lacks its capability to suppress inflammation, such as degradation of neuropeptides and proteins. The dysregulation of these proteinases exists already in non-lesional skin of AD and NE.     

Mast cell chymase is increased in chronic atopic dermatitis but not in psoriasis

Mast cell chymase is a chymotrypsin-like serine proteinase primarily stored in secretory mast cell granules. Mast cell chymase has various effects on angiotensin, metalloproteases, lipoproteins, procollagen, neuropeptides and cytokines. Recent studies have demonstrated that chymase inhibitors inhibit skin inflammation. In this study we sought to determine the role of mast cell chymase in atopic dermatitis (AD) in comparison with its role in psoriasis and normal skin. Skin biopsy specimens were obtained from non-lesional and lesional skin of patients with chronic AD and psoriasis and from normal skin of non-atopic and non-psoriatic controls. The number of mast cells containing chymase was determined by immunohistochemistry using a chymase-specific monoclonal antibody. A significantly (P<0.05) enhanced number of chymase-positive cells was found in lesional AD skin as compared to normal skin as well as to lesional and non-lesional skin of patients with psoriasis. A significant (P<0.05) increase in the number of chymase-positive cells was also found in non-lesional AD skin in comparison to psoriasis. An enhanced, albeit not statistically significant difference was noted in non-lesional AD skin as compared to normal skin. In conclusion, these results suggest that mast cell chymase may play an integral part in eliciting and maintaining cutaneous inflammation in AD but not in psoriasis. The increased proteinase activity of mast cell chymase may also be involved in promoting a skin barrier defect in AD, which subsequently enhances the skins permeability to allergens and microbes and thereby aggravates the eczema.     

MAST CELL TRYPTASE AND CHYMASE ARE POTENTIAL REGULATORS OF NEUROGENIC INFLAMMATION IN PSORIATIC SKIN

Background. Tryptase and chymase are proteinases present only in mast cells. In psoriatic lesions, mast cells are increased in number. Certain neuropeptides are also more abundant in lesional than nonlesional psoriatic skin. Based on some earlier results as well as the results of the present study, a hypothesis is presented concerning the regulatory action of mast cell tryptase and chymase on neuropeptides in psoriatic inflammation. Methods. Forty patients were biopsied, 13 for a mature psoriatic plaque and 9 patients of 27 for a developing (1–3 weeks) psoriatic lesion induced by tape stripping (Koebner reaction). Each lesion had its nonlesional control from the same patient. Mast cell tryptase and chymase, and the neuropeptides Substance P (SP) vasoactive intestinal polypeptide (VIP), and calcitonin-gene-related peptide (CGRP) were stained by enzyme-and immunohistochemical methods. Morphological contacts between mast cells and neuropeptides were visualized using double stains and quantitated in the upper dermis. Results. As the lesion aged, MCTC mast cells displaying tryptase activity increased in number, whereas chymase activity in these cells decreased. All neuropeptides showed some increase along with the development of the lesion, but SP was most abundant in mature lesions. Substance P-positive nerves had also more contacts with mast cells compared to VIP- or CGRP-containing fibers, the contact count being highest in mature lesions. Conclusions. Tryptase is known to degrade VIP and CGRP, but not SP. Chymase is capable of cleaving both SP and VIP, but is rendered partially inactive in psoriatic skin. These data together with the results of the present study strongly suggest that SP has potency to act as an important mediator in different stages of the psoriatic inflammation.     

Quantitative analysis of contact sites between mast cells and sensory nerves in cutaneous psoriasis and lichen planus based on a histochemical double staining technique

Summary The aim of the present study was to test further our previous hypothesis that the inflammatory reaction in psoriasis is neurogenic. For this purpose, contact sites between mast cells and sensory nerves were morphometrically analysed in the basement membrane zone, papillary dermis and three dermal zones of lesional/non-lesional psoriatic and lichen planus skin as well as in healthy control skin. The analyses were made on sections stained with a histochemical double stain developed for this study. With the double stain, active mast cell tryptase was stained blue enzyme histochemically, and the sensory nerves black using specific monoclonal anti-neurofilament antibodies with immunogold. In psoriatic lesions, both mast cells and mast cell — nerve contacts were markedly more frequent in the basement membrane zone and in the papillary dermis when compared with the corresponding areas in the other groups. Mast cell numbers were increased in both lesional and symptom-free skin in lichen planus, but no increase was found in the mast cell — nerve contacts. Increased contacts between mast cells and sensory nerves indicate that the elements exist for neurogenic inflammation in psoriatic lesions. These increased contacts are not due to the extensive inflammatory reaction only, because they were not observed in lichen planus lesions.     

Mast cells in the cutaneous lesions of sarcoidosis: their subtypes and the relationship to systemic manifestations

Possible involvement of mast cells in pulmonary sarcoidosis has been suggested, however whether mast cells are involved in cutaneous sarcoidosis remains unknown. We undertook a morphological study of mast cells in the lesional skin from 17 patients with cutaneous sarcoidosis using immunohistochemical methods. Mast cells were present in non-parenchymal fibrous areas, but not in granulomatous areas, in the biopsy specimens from the cutaneous lesions. However, there were no significant differences between the number of mast cells in the lesional skin and that in non-lesional skin from the patients. Mast cells containing substantial quantities of both tryptase and chymase (MC(TC) cells) were present in 41% of the patients, and cells containing tryptase but not chymase (MC(T) cells) were present in 59% of patients. All patients of the former group showed systemic manifestations of the disease concomitantly. Serum angiotensin I-converting enzyme levels were elevated in 71.4% of the former group, and in 30% of the latter group. This study for the first time demonstrated that mast cells were present in non-parenchymal fibrous areas of the cutaneous lesions of sarcoidosis, and the mast cell subtypes may be related to systemic manifestations.     

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). Moreover, the staining intensity of IL-4 in mast cells was clearly increased in the lesional compared with the non-lesional AD skin. Mast cells appeared to be the main cell type containing IL-4 in 40% of the lesional AD skin specimens, whereas in the remaining 60% prominent IL-4-positive mononuclear cell infiltrates were also present. In the non-lesional skin, mast cells appeared to be the main cell type containing IL-4 in all specimens. These results indicate that mast cells are one major source of IL-4 in lesional and non-lesional AD skin, and they could contribute significantly to the development of AD.     

Dermal mast cells in scleroderma: their skin density, tryptase/chymase phenotypes and degranulation

To determine the distribution, tryptase/chymase phenotypes and degranulation of mast cells (MCs) in the dermis of patients with scleroderma, we examined MC density in the skin of 22 patients with systemic sclerosis (SSc) and 11 with localized scleroderma (LSc). We used antitryptase and antichymase antibodies after Carnoy's fixation. Detailed reports of two representative patients with SSc and LSc are included. In the scleroedematous stage (grade 1) showing oedema in both papillary and reticular dermis with variable homogenization of collagen bundles in the reticular dermis, MC skin density was variable in each specimen although MC skin density, as a whole, was significantly increased as compared with normal skin ( P  < 0.05). In the sclerotic stage (grade 2) characterized by homogenization of collagen bundles in the entire dermis, MC skin density was significantly decreased as compared with normal skin ( P  < 0.005). LSc showed changes similar to those in SSc. The ratio of MC_TC cells (both tryptase- and chymase-positive MC) to MC_T cells (tryptase-positive but chymase-negative MC) was variable in SSc and LSc. MC_T cells were exclusively dominant in three patients with SSc and two with LSc. In a patient with SSc (patient 1) showing remarkable perivascular and interstitial oedema in the upper dermis, MC skin density was increased in the oedematous portion and tryptase-positive granules were distributed in extracellular locations. In another patient with LSc (patient 2), tryptase positivity increased and chymase positivity decreased in both number and intensity as the skin sclerosis progressed. MCs must have variable interactions with the lesional skin in SSc and LSc. The present study suggests that MCs are involved in the development of interstitial oedema.     

The production of collagen and the activity of mast-cell chymase increase in human skin after irradiation therapy

Fibrosis is a common complication of radiotherapy. The pathogenesis of radiation-induced fibrosis is not known in detail. There is increasing evidence to suggest that mast cells contribute to various fibrotic conditions. Several mast-cell mediators have been proposed to have a role in fibrogenesis. Tryptase and chymase, the predominant proteins in mast cells, have been shown to induce fibroblast proliferation and collagen synthesis in vitro. In order to explore the role of mast cells in irradiation-induced fibrosis, we analyzed skin biopsies and suction blister fluid (SBF) samples from the lesional and healthy-looking skin of 10 patients who had been treated for breast cancer with surgery and radiotherapy. The biopsies were analyzed histochemically for mast-cell tryptase, chymase, kit receptor, and tumor necrosis factor-alpha. Skin collagen synthesis was assessed by determining the levels of type I and III procollagen amino-terminal propeptides (PINP and PIIINP) in SBF and using immunohistochemical staining for PINP. Immunohistochemical stainings for prolyl-4-hydroxylase reflecting collagen synthesis and chymase immunoreactivity in irradiated and control skin were also performed. The mean level of procollagen propeptides in SBF, which reflects actual skin collagen synthesis in vivo, was markedly increased in irradiated skin compared to corresponding healthy control skin areas. The mean number of PINP-positive fibroblasts was also significantly increased in the upper dermis of radiotherapy-treated skin. The number of cells positive for tryptase, chymase and kit receptor was markedly increased in irradiated skin. In addition, using double-staining techniques, it was possible to demonstrate that in some areas of the dermis, tryptase-positive mast cells and fibroblasts are closely associated. These findings suggest a possible role of mast cells in enhanced skin collagen synthesis and fibrosis induced by radiotherapy.     

The development of manifest psoriatic lesions is linked with the invasion of CD8+ T cells and CD11c+ macrophages into the epidermis

Koebner response was studied in 35 psoriatic patients. Two punch biopsies per patient were taken from non-lesional psoriatic skin before, and 6 h, 2 days, 7 days, 14 days and 21 days after, tape stripping. Alterations in the numbers of CD1+ Langerhans cells, CD4+ and CD8+ T cells and CD11c+ macrophages were mapped morphometrically. Results were compared with lesional and non-lesional psoriatic skin, and control skin. Nine of 35 patients were Koebner-positive. No statistically significant differences were noted between non-lesional psoriatic and control skin. CD4+ T cells increased in number 2 days after trauma in both the epidermis and the dermis, whereas epidermal CD8+ T cells and CD11c+ macrophages increased only in the Koebner-positive lesional skin after 7 days. The changes in lesions induced by tapestripping resembled those seen in lesional psoriatic skin (mature plaques). The number of CD1+ cells increased in mature psoriatic lesions only. It seems possible that trauma per se stimulates the accumulation of CD4+ T cells at the site of injury, but the development of manifest psoriatic lesions correlates with invasion of CD8+ T cells and CD11c+ macrophages into the epidermis.     

The presence of tryptase-positive and bikunin-negative mast cells in psoriatic skin lesions

Human mast cells are well known to produce a serine protease, tryptase, which appears to play a pathogenic role in various skin inflammations. It was previously reported that a rat homologue of bikunin may inhibit tryptase activity. Various type of cells (i.e. keratinocytes) are able to produce this protein inhibitor, it still remains unclear if bikunin is present in dermal inflammatory milieu, in which mast cells, through secretion of tryptase, play an inflammatory role. Therefore, the purpose of the present study was to exploit expression and production of bikunin in dermis and dermal constituents. We first compared the dermal mast cells in psoriatic lesions with those in lesional skin of atopic dermatitis or of chronic eczema by use of immunoelectron microscopy and immunohistochemical analyses using antibodies to bikunin and tryptase. Then, we tested what kinds of cytokines may regulate the de novo synthesis of bikunin. To do so, RNA was extracted from a human mastocytic cell line, HMC-1, reverse-transcribed, and semiquantitative RT-PCR was performed using primers specific for bikunin. With immunoelectron microscopy, bikunin was found to localize on the cell membrane, while tryptase was in the secretary granules of the mast cells. In psoriatic lesions, around 70% of dermal mast cells were positive for both tryptase and bikunin, and the remaining was mostly positive for tryptase, but the expression of bikunin was under the detection limit of the experimental setting. This observation was seen in only psoriatic lesions, even in almost cured lesions, while in atopic dermatitis or chronic eczema only mast cells doubly positive for bikuin and tryptase were seen. In HMC-1, bikunin was constitutively expressed at an mRNA level, which was upregulated by stimulation with interleukine-4, but was suppressed by interferon-γ. Bearing in mind the concept that in psoriasis local cytokine milieu is shifted toward a Th1 pattern (predominant secretion of interferon-γ), tryptase-positive, bikunin-negative mast cells may be induced.     

Mast cell chymase is present in uterine cervical carcinoma and it detaches viable and growing cervical squamous carcinoma cells from substratum in vitro

Increased numbers of mast cells is a typical feature of a variety of human cancers. The major mediators in the secretory granules of the MC_TC type of mast cells, serine proteinases tryptase and chymase, may be involved in squamous cell carcinoma (SCC) lesions by inducing matrix remodeling and epithelial cell detachment. The objective of this study was to analyze immunohistochemically whether MC_TC mast cells as well as protease inhibitors, squamous cell carcinoma antigens (SCCAs), are present in the uterine cervical SCC. In addition, the effect of tryptase and chymase on uterine cervical SCC cell lines was studied in vitro. Here we report that tryptase- and chymase-positive mast cells are present in significant numbers in the peritumoral stroma of SCC lesions. Also, weak SCCA-2 immunoreactivity is observed in the SCC lesions, but only SCCA-1 in uterine cervical specimens with nonspecific inflammation. In cell cultures, especially chymase, but not tryptase, was shown to induce effective detachment of viable, growing and non-apoptotic SiHa SCC cells from substratum. Chymase also detached viable ME-180 SCC cells from substratum as well as degraded fibronectin. In contrast, normal keratinocytes underwent apoptotic cell death after similar prolonged chymase treatment. No inhibition of chymase was detected by SiHa cell sonicates nor did these cells express marked SCCA immunopositivity. MC_TC mast cells containing tryptase and chymase are present in the peritumoral stroma of uterine cervical SCC and the malignant cells are only weakly immunoreactive for the chymase inhibitor SCCA-2. It is chymase that appears to be capable of inducing effective detachment of viable and growing SCC cells and therefore, it may release SCC cells from a tumor leading to spreading of malignant cells.     

The skin in mastocytosis.

The most frequent site of organ involvement in patients with any form of mastocytosis is the skin. Cutaneous expressions include urticaria pigmentosa, mastocytoma, diffuse and erythrodermic cutaneous mastocytosis, and telangiectasia macularis eruptiva perstans. The cutaneous lesions tend to appear early in life. Although urticaria pigmentosa has been reported in 12 pairs of twins and one set of triplets, the majority of affected individuals have no familial association. Most patients with systemic mastocytosis have skin lesions; however, an occasional patient will have systemic disease with no other skin features than flushing. In lesional cutaneous sites and in non-lesional skin, there is an increase in the number of mast cells. Electron microscopy shows quantitative differences between lesional skin mast cells from patients with and without systemic disease. The mast cells from adult patients with systemic disease have a larger mean cytoplasmic area, nuclear size, and granule diameter. The granules contain predominantly grating/lattice structures. The cutaneous mast cells contain tryptase and chymase. They retain their functional reactivities to relevant secretory stimuli, such as C3a, morphine sulfate, and calcium ionophore A23187. Lesional skin contains histamine, leukotriene B4, prostaglandin D2, 5-hydroxyeicosatetraenoic acid, platelet-activating factor, and heparin. Treatment of the cutaneous manifestations includes the use of H1 and H2 antihistamines, oral disodium cromoglycate, psoralens plus ultraviolet A photochemotherapy, and potent topical corticosteroid preparations.     

Mast cell density in psoriatic skin. The effect of PUVA and corticosteroid therapy

Summary Numbers and volume fractions of mast cells in nonlesional and chronic lesional skin of psoriatic patients were compared with those of normal control skin. Mast cell densities were similar in psoriatic nonlesional and normal control skin. The superficial dermis of lesional psoriatic skin contained more mast cells than either normal or nonlesional psoriatic skin. Neither PUVA nor corticosteroid treatment for 3–4 weeks significantly reduced mast cell numbers or volume fractions in lesional skin, although both treatments clinically and histologically markedly improved the lesions. The results indicate that the initiation of the healing process in psoriatic plaques is not correlated with the mast cell density. The remaining high mast cell density may be normalized later, or after a longer therapy.     

The increase in tryptase- and chymase-positive mast cells is associated with partial inactivation of chymase and increase in protease inhibitors in basal cell carcinoma

BACKGROUND: In basal cell carcinoma (BCC), mast cells accumulate in the peritumoral stroma. The serine proteinases tryptase and chymase are the major mediators in mast cell granules and they may exert their enzymatic activity in the BCC lesion by inducing matrix remodeling and epithelial cell detachment. OBJECTIVE: To analyse the numbers of mast cells showing tryptase enzyme activity, chymase enzyme activity and chymase immunoreactivity as well as the presence of chymase inhibitors alpha(1)-antichymotrypsin (alpha(1)-AC), alpha(1)-proteinase inhibitor (alpha(1)-PI) and squamous cell carcinoma antigen-2 (SCCA-2) in BCC. METHODS: Eleven biopsies were taken from the lesion and healthy-looking skin of 10 patients with superficial spreading BCC. The frozen biopsies were analysed enzyme- and immunohistochemically, and a sequential double-staining method was applied. RESULTS: In the BCC lesion, the number of mast cells with tryptase activity and chymase immunoreactivity was significantly increased by 2.2- to 2.3-fold. Practically all tryptase-immunopositive cells contained tryptase activity although occasional tryptase-immunopositive cells (about 1% of total) revealed no activity. However, the ratio of cells with chymase activity to those with chymase immunoreactivity was significantly decreased from 49 +/- 19% in the healthy skin to 33 +/- 19% in the BCC lesion. Instead, the percentage of mast cells displaying alpha(1)-AC or alpha(1)-PI immunoreactivity was significantly increased by 1.7-fold in the BCC lesion. SCCA-2 expression was strongly increased in the malignant BCC epithelium but mostly in the suprabasal layers. CONCLUSIONS: Tryptase- and chymase-positive mast cells (MC(TC)) increased in the BCC lesion. However, chymase is partially inactivated, possibly by the effective chymase inhibitors alpha(1)-AC and alpha(1)-PI. SCCA-2 increased in BCC, but was localized mostly to the suprabasal layers, and thus it seems not to be crucial in inhibiting chymase.     

The development of manifest psoriatic lesions is linked with the appearance of ICAM-1 positivity on keratinocytes

The development of psoriatic lesions was studied in 36 psoriatic patients using the Koebner reaction induced by tape stripping. Two biopsies per patient were taken from non-lesional psoriatic skin before, and 6 h, 2 days, 7 days, 14 days and 21 days after tape stripping. Alterations in HLA-DR, ICAM-1, Ki-67 and FXIIIa positivities in both the dermis and the epidermis were estimated using immunohistochemical methods. A double staining for CD4⁺ and CD8⁺ T cells was also carried out to show their possible Ki-67 positivity. Results were compared with those from lesional (mature plaque) and non-lesional psoriatic skin, and control skin. Of the 36 patients, 9 were Koebner-positive. The most important finding in Koebner-positive psoriatic skin was the appearance of ICAM-1 positivity on epidermal keratinocytes simultaneously with the clinically observed lesion on day 7. The number of FXIIIa⁺ dendrocytes in the dermis was quite constant, and increased in mature psoriatic lesions only. The number of active HLA-DR⁺ immunocompetent cells increased in developing psoriatic lesions, being highest in mature lesions, but no Ki-67 positivity was detected in epidermal or dermal T cells in the psoriatic specimens. Based on these results, it is concluded that T cells divide and are activated extracutaneously in psoriasis, and also that ICAM-1/LFA-1 interactions are important in the recruitment of inflammatory cells and in controlling the effector cell functions.