NKp46 regulates the production of serine proteases and IL-22 in human mast cells in urticaria pigmentosa

NKp46 (natural cytotoxic receptor 1/CD335) is expressed on natural killer cells and Th2-type innate lymphocytes. However, NKp46 expression in human mast cells has not yet been reported. Here, we explored the expression of, and possible role played by, NKp46 in such cells. NKp46 protein was expressed in human mast cells in urticaria pigmentosa principally of the tryptase-positive/chymase-negative type (MCT), but not in human non-neoplastic skin mast cells of the tryptase-positive/chymase-positive (MCTC) type. NKp46 expression was also evident in the human neoplastic mast cell line HMC1.2. NKp46 knockdown changed the phenotype of this cell line from MCT to MCTC and downregulated GrB production, but did not influence IL-22 production. An agonistic anti-NKp46 antibody upregulated production of GrB and IL-22, but did not change the MCT-like phenotype of HMC1.2 cells. NKp46 was thus involved in the production of serine proteases and IL-22 in human mast cells.

Urticaria pigmentosa and mastocytosis: the role of immunophenotyping in diagnosis and determining response to treatment

Recent advances in our understanding of mast cell biology and disease resulted in identification of important differences in expression of mast cell surface antigens in normal and neoplastic mast cells. Most notably, detection of aberrant expression of CD25 and CD2 on the surface of neoplastic mast cells but not on their normal counterparts leads to the inclusion of this immunophenotypic abnormality in the World Health Organization's diagnostic criteria for systemic mastocytosis. Aberrant mast cell surface marker expression can be detected in the bone marrow aspirate by flow cytometry, even in patients with limited disease that lacks histopathologically detectable aggregates of mast cells in bone marrow biopsy sections. Flow cytometric analysis of bone marrow mast cells is therefore a sensitive method of diagnosis of mast cell disease and is expected to find increasing use in determining response to emerging mast cell cytoreductive therapies.

Diagnosis of mastocytosis: value of cytochemistry and immunohistochemistry

The diagnosis of mastocytosis or mast cell disease may be difficult sometimes because of the wide variety of clinical presentation, abnormal morphology of mast cells, and variation in histologic features which may mimic varieties of other diseases. Over the years, several cell type specific cytochemical and immunochemical markers have been used for the identification of hematopoietic cells in order to establish the accurate diagnosis of mastocytosis and their associated hematologic diseases. Cytochemical stain for aminocaproate esterase is the most specific enzyme marker for identification of mast cells on cytologic specimens and the immunohistochemical stain for tryptase and/or c-kit has also been established as a sensitive and specific marker for mast cells in paraffin sections.

Enhanced expression of SCF in the dermis is a prognostic factor for the regression of urticaria pigmentosa

Urticaria pigmentosa (UP) is a disorder of mast cell proliferation that occurs in cutaneous tissue. Most patients whose skin manifestations appear in infancy or childhood, experience a resolution of the disease by adolescence. In order to elucidate the relationship between mast cell character and UP prognosis, we used an immunohistochemical approach to examine the expression of stem cell factor (SCF) and c-Kit in the skin of patients with UP. The results revealed intercellular SCF expression throughout the dermis in improving cases. On the other hand, in cases with a tendency to worsen, dermal SCF was recognized only partially or not at all. Regardless of the clinical course, intracellular SCF immunoreactivity of the entire epidermis increased in cases of child onset UP. The c-Kit expression of mast cells in all UP patients showed no relation to clinical features. These findings suggest that SCF in the dermis promotes the differentiation of mast cells infiltrating in UP, and might be an attractive candidate to induce the remission of UP.

Serum tryptase measured with B12 and G5 antibody-based immunoassays in mastocytosis patients and its relation to histamine turnover

Serum tryptase was measured with the B12 and G5 antibody-based immunoassays in 25 adult patients with mastocytosis and in 18 controls. Twelve patients had uncomplicated cutaneous mastocytosis (urticaria pigmentosa) and 13 had urticaria pigmentosa with systemic symptoms. Tryptase levels were compared with histamine turnover estimated as urinary excretion of the main histamine metabolite tele-methylimidazoleacetic acid. Elevated B12 tryptase levels (> 20 microg/L) were found in most mastocytosis patients, including five of eight patients with only cutaneous manifestations who had a low urinary histamine metabolite excretion. This indicated a higher sensitivity for diagnosing mild mastocytosis on the basis of levels of serum tryptase as opposed to urinary methylimidazoleacetic acid. However, the serum B12 tryptase assay could not differentiate between urticaria pigmentosa patients with and without systemic disease: the measurement of histamine metabolite excretion probably reflects the mast cell burden more accurately. Serum G5 tryptase levels were generally low in both controls and mastocytosis patients.

C5a receptors are detectable on mast cells in normal human skin and in psoriatic plaques but not in weal and flare reactions or in uticaria pigmentosa by immunohistochemistry

The expression of the receptor for the anaphylatoxin C5a on mast cells was studied with three monoclonal antibodies directed to the N-terminal domain of the C5a receptor. Human skin was investigated by immunohistology applied to sequential 2 micron sections of acrylate-embedded tissues. All anti-C5a receptor antibodies stained c-kit+ or tryptase+ cells which were metachromatic after toluidine blue staining in normal human skin. The binding of anti-C5a receptor antibodies was inhibitable by a peptide representing the first 31 amino acids of the C5a receptor. A similar expression of C5a receptors was found on mast cells in chronic psoriatic plaques. However, C5a receptors were not detectable on mast cells in weal and flare reactions or in lesional skin of uticaria pigmentosa. These findings suggest that (1) anti-C5a receptor antibodies directed to the N-terminal domain of the receptor are suitable tools for the identification of mast cells in acrylate-embedded sections of human skin, (2) mast cell activation in weal and flare reactions results in C5a receptor downregulation or receptor blockade and (3) mast cells in urticaria pigmentosa lack a typical marker of normal human skin mast cells.

Expression of stem cell factor in cutaneous mastocytosis

Stem cell factor has recently been identified as a potent growth factor for bone marrow stem cells, melanocytes and mast cells. In order to evaluate its possible role in human mastocytosis, skin lesions from 13 patients with urticaria pigmentosa and five patients with mastocytomas, and normal skin specimens from five healthy donors were studied by immunohistochemistry, using polyclonal and monoclonal (hkl-12) antibodies against stem cell factor, and a monoclonal antibody (YB5.B8) against its receptor, the c-kit proto-oncogene product. Stem cell factor expression was noted in all sections studied, with an equal distribution pattern for both antibodies, but a weaker intensity with the hkl-12 reagent. Cytoplasmic staining was noted in keratinocytes, Langerhans cells, sweat gland ductal lining cells, mast cells, endothelial cells and spindle-shaped dermal stromal cells. An intense, diffusely granular reaction pattern was noted in all cells, except for a sparse, coarsely granular pattern in mast cells and stromal cells. In urticaria pigmentosa, staining was weaker in keratinocytes, but more prominent in Langerhans cells. In all sections, toluidine blue-positive mast cells and TA 99-positive basal epidermal melanocytes were the only cells to react with the c-kit antibody. Mastocytomas and urticaria pigmentosa lesions thus exhibit different patterns of stem cell factor expression. However, a possible pathogenetic role of this factor in mastocytosis remains to be determined.

Phenotypic characterization of skin lesions in urticaria pigmentosa and mastocytomas

In order to identify possible cellular abnormalities in human mastocytosis, sections from 13 urticaria pigmentosa lesions and 5 mastocytomas were compared with 5 normal skin specimens using histochemical, enzyme histochemical and immunohistochemical techniques. All toluidine blue-positive mast cells also reacted with Fc epsilon RI and c-kit antibodies, almost all stained for tryptase, many for chymase and the myeloid workshop mast cell antibodies, few for Fc epsilon RII and none for the proliferation marker Ki-67. Urticaria pigmentosa lesions contained fewer epidermal Langerhans cells and a lower percentage of avidin-positive mast cells than mastocytomas and normal skin. Mastocytomas exhibited generally weaker staining for mast cell markers and mostly lacked Fc epsilon RI-bound IgE on mast cells and Langerhans cells, although the receptor was able to bind IgE in tissue sections. Most of the mast cell antibodies also reacted with other cell types. Only toluidine blue, avidin, tryptase and chymase stains were mast cell specific. Mast cells in mastocytosis thus differed only to a minor degree from normal mast cells, although distinct pathomechanisms may play a role in urticaria pigmentosa and mastocytosis.

Human mast cells produce type VIII collagen in vivo

Mast cells are assuming importance not only in their familiar role in acute allergic and parasitic diseases but also in chronic inflammatory, immunologic and fibrotic states. The processes by which human extracellular matrices are influenced by mast cells have remained obscure. We report here the production of type VIII collagen by human mast cells. Mast cells representing each of the known phenotypes were identified in a variety of tissues using histochemical techniques, and monoclonal antibodies specific for tryptase, chymase, and c-kit. Mast cells in normal and pathologic tissues expressed type VIII collagen alpha-1 chain protein and mRNA, detected by immunohistochemistry using monoclonal and polyclonal antibodies, and non-isotopic oligonucleotide in situ hybridization using digoxigenin-labelled oligonucleotide probes based on the published human alpha-1 collagen VIII sequence. Perivascular location of type VIII collagen positive mast cells was a striking finding. The secretion of type VIII collagen by mast cells in vivo may contribute to angiogenesis, tissue remodelling, and fibrosis.

Plasma concentrations and urinary excretion of regulatory peptides in patients with urticaria pigmentosa

Patients with urticaria pigmentosa were investigated during symptom-free interval regarding plasma concentrations and urinary excretion of immunoreactive regulatory peptides: calcitonin gene-related peptide (CGRP), gastrin, neurokinin A (NKA), neuropeptide Y (NPY), somatostatin (SOM), substance P (SP) and vasoactive intestinal peptide (VIP). The plasma concentrations of these peptides, except for CGRP, were below the detection limit. The urinary excretion of the regulatory peptides were not higher in the patient group than in the controls, but in individual patients there was high urinary excretion of SP and VIP. A lower urinary excretion of CGRP was found in the patient group in addition to a tendency to a lower plasma concentration.

Immunohistochemical characterization of human cutaneous mast cells in urticaria pigmentosa (cutaneous mastocytosis)

To clarify the origin and function of human cutaneous mast cells (CMCs), immunohistochemical characterization was done in 19 cases of urticaria pigmentosa (cutaneous mastocytosis) using 9 antibodies (anti-leukocyte common antigen, MX-PanB, anti-lysozyme, anti- alpha 1-antitrypsin, anti- alpha 1-antichymotrypsin, anti-vimentin, anti-neuron-specific enolase, anti-factor VIII-related antigen, and anti-ACTH). CMCs showed positive reactions with anti-alpha 1-antichymotrypsin and anti-vimentin in almost all of the specimens. In more than half of the specimens, CMCs were stained positively with anti-alpha 1-antitrypsin, MX-PanB, and anti-factor VIII-related antigen. Anti-leukocyte common antigen and anti-ACTH also showed positive reactions in some specimens. These results confirm the existence of vimentin filaments in CMCs and suggest a functional role of CMCs in hemostasis via factor VIII. Furthermore, immunohistochemical similarity between CMCs and granulocyte/macrophage-group cells is also suggested.

Immunohistochemical demonstration of migration inhibitory factor in different types of urticaria

Because urticarial lesions can persist for extended periods of time, we have investigated the histochemical expression of an antibody against the cytokine macrophage inhibitory factor in 23 patients with different types of urticaria. Positive staining of upper and middermal dendritic cells was noted in sections from all three biopsy specimens of acute urticaria, eight of chronic urticaria, and all six of urticaria pigmentosa lesions. In all but one biopsy specimen, endothelial cells reacted as well. In three sections (two chronic urticaria, one urticaria pigmentosa), luminal lining cells of sweat glands were also noted to stain positively. In contrast, lesional skin from all eight patients with pressure urticaria was negative, as was the clinically normal skin of all patients, with the exception of one patient with urticaria pigmentosa. The data suggest that cytokines may be involved in lesions of acute type immunologic processes and that they need not be expressed in delayed type reactions.

Mechanisms for hyperpigmentation in postinflammatory pigmentation, urticaria pigmentosa and sunburn

Our in vitro studies demonstrate that normal human epidermal melanocytes become swollen and more dendritic with an increase in amount of immunoreactive tyrosinase when they are cultured for several days with arachidonic acid metabolites, vitamin D3 or histamine. From these data we propose the following possible mechanisms for hyperpigmentations noted at postinflammatory sites and suntanned areas as well as at skin lesions of urticaria pigmentosa. Arachidonic acid metabolites and histamine, which are found in increased amounts in inflammatory skin, are thought to play a key role in the induction of postinflammatory hyperpigmentation. In sunburnt skin the increased proinflammatory mediators, particularly arachidonic acid metabolites, are also thought to stimulate melanocytes in the production of hyperpigmentation. Thus tanning after sun exposure may be induced not only by the effect of vitamin D3 and direct UV irradiation on the melanocytes but also by the effect of various arachidonic acid metabolites which are increased in sunburnt skin. Mast cells massively proliferate in the skin lesions of urticaria pigmentosa. Thus hyperpigmentation in the skin lesions of urticaria pigmentosa is quite likely to be induced by the chemical mediators, including histamine and leukotrienes, that are released from these cells.

Effects of isoprenaline and terbutaline on urinary excretion of histamine and its two main metabolites in systemic mastocytosis

Both short-term and long-term effects of the beta-sympathomimetic drugs isoprenaline and terbutaline on the urinary excretion of histamine and its two main metabolites were evaluated in patients with systemic mastocytosis. In a short-term study isoprenaline and terbutaline were given intravenously during five hours to three and two patients, respectively. Compared with placebo infusion Nt-methylhistamine excretion fell during terbutaline administration, whereas during isoprenaline no changes were observed. In a long-term study three patients received a treatment with orally administered terbutaline for 24 days. In one patient a slight reduction of the excretion of the histamine metabolites was found. In another patient the excretion of histamine and its metabolites decreased especially during the eight days observation period after the end of the treatment. In this study we saw occasionally large and rapid changes occurring simultaneously in all three urinary parameters of histamine release. In conclusion, terbutaline can reduce histamine release in systemic mastocytosis. However, because of the small symptomatic and biochemical effects found in our patients, the clinical significance of beta-sympathomimetic drug treatment in this disease has yet to be established.

Differences between basophils and mast cells: failure to detect Charcot-Leyden crystal protein (lysophospholipase) and eosinophil granule major basic protein in human mast cells

Human eosinophils contain several distinctive proteins including eosinophil granule MBP and the membrane-associated CLC protein (lysophospholipase). Human basophils also contain these proteins, indicating biochemical similarities between eosinophils and basophils. To determine whether MBP or CLC protein is present in connective tissue mast cells, we studied human lung and cutaneous mast cells by immunofluorescence by utilizing specific antibodies to CLC and MBP. Cytocentrifuge slides of enriched lung mast cells and mast cells in sections of formalin-fixed, paraffin-embedded cutaneous tissue from urticaria pigmentosa lesions were stained for CLC and MBP. Neither pulmonary nor cutaneous mast cells stained for CLC protein or MBP. In contrast, lung and cutaneous eosinophils in the same preparations showed bright staining for both proteins. The failure to find CLC protein and MBP in mast cells provides additional evidence of dissimilarity between mast cells and basophils, and an immunochemical means to distinguish between them.

Treatment of urticaria pigmentosa with corticosteroids

Based on a previous observation that the long-term application of potent topical corticosteroids under occlusion to normal skin resulted in the loss of mast cells, we investigated the effects of intralesional and topical steroids in urticaria pigmentosa (UP). Three patients with UP had lesions that were injected with triamcinolone acetonide. Four weeks after injection, all patients showed a loss of Darier's sign, and, by eight weeks after injection, there was a dramatic clearing of the plaques and a decrease in brown hyperpigmentation. By 12 weeks, mast cells were undetectable by light microscopy and transmission electron microscopy (TEM). The injection sites remained dramatically improved for as long as one year after treatment, and histamine content was reduced 95% in one patient 48 weeks after injection. In six patients, the topical application of 0.05% betamethasone dipropionate under occlusion to limited areas induced almost complete clearing of UP lesions. Lesions treated with an emollient under occlusion, as a control, demonstrated no change. After treatment, no mast cells were seen by light microscopy or TEM, and this persisted for at least 24 weeks. There was also a significant decrease in tissue histamine levels in the treated areas. The treated areas remained clinically improved for at least nine to 12 months. These data indicate that steroid therapy dramatically decreases the excess number of normal-appearing mast cells in UP as well as induces a prolonged resolution of UP lesions. Local corticosteroids thus are a useful therapeutic modality for UP.

Metabolic fate of endogenously synthesized prostaglandin D2 in a human female with mastocytosis

Increased production of prostaglandin D2 was recently demonstrated in patients with systemic mastocytosis. One female patient investigated with mastocytosis was found to have overproduction of prostaglandin D2 of such magnitude (150-fold above normal) that it provided the unique opportunity to delineate the metabolic fate of endogenously synthesized prostaglandin D2. A five percent aliquot of a twenty-four hour urine collection from this patient was extracted, purified by silicic acid chromatography, methylated, and finally subjected to high pressure liquid chromatography. Column fractions collected were derivatized and analyzed by gas chromatography-mass spectrometry. Increased quantities of sixteen urinary metabolites were identified and included a series of metabolites retaining the PGD-ring as well as a series of metabolites with a PGF-ring. PGF-ring metabolites were excreted in approximately 4-fold greater relative abundance than PGD-ring metabolites. More than one apparent isomeric form of some PGF-ring metabolites were found. The predominant urinary metabolite was 2,3-dinor-prostaglandin F2. This study provides evidence that endogenously synthesized prostaglandin D2 is converted in substantial part to prostaglandin F2 metabolites in vivo in humans.

Treatment of two mastocytosis patients with a histidine decarboxylase inhibitor

Alpha-fluoromethylhistidine, alpha-FMH (L-641.575, Merck, Sharp and Dohme), a specific irreversible inhibitor of the mammalian histidine decarboxylase, was investigated for its effect on possible histamine symptoms in mastocytosis. Two patients were treated for 28 and 22 weeks respectively. The first patient had systemic mastocytosis and a severe malabsorption causing weight loss, excessive fecal fat losses and electrolyte disturbances, the main symptom being frequent diarrhoea. The second patient had mainly skin manifestations diagnosed as urticaria pigmentosa and the main symptom was pruritus. There were no side effects of the drug. The first patient produced formed stools after one week of treatment, concomitant with a decrease in plasma histamine and in urinary excretion of the main histamine metabolite tele-methylimidazoleacetic acid (MeImAA). In the second patient definite benefit of the treatment was observed after two months. However, changes in histamine parameters occurred earlier. Plasma histamine and urinary MeImAA were reduced after one week and in two or three weeks reached a steady-state level of about 25% of pretreatment values. The results indicate an effective inhibition of histamine synthesis in both patients but only the diarrhoea seemed to be causally related to the change in histamine metabolism.

Suppression of T lymphocyte mitogen response in patients with mastocytosis

Immunological functions were studied in 22 patients with mastocytosis. Lymphocyte stimulation with concanavalin A (Con A) and phytohemagglutinin showed that the patients responded with lower mitogenic activity than healthy controls. Furthermore, the lymphocytes of patients with the most extensive mast cell disease had a significantly lower Con A mitogen response than the lymphocytes of the rest of the patients. The effect of histamine and its specific metabolites, tele-methylhistamine and tele-methylimidazoleacetic acid (MeImAA), on the Con A lymphocyte mitogen response was also studied in healthy controls. Histamine had a clear suppressive effect, while the metabolite tele-methylhistamine caused only slight inhibition and MeImAA apparently had no effect. The total T cell, suppressor and helper cell numbers, measured with monoclonal antibodies, and the amount of immunoglobulins in serum were found to be normal.

HLA and lymphocyte histamine sensitivity in mastocytosis

HLA-ABC and DR typing was performed on 50 patients with mastocytosis. Lymphocyte stimulation with concanavalin A has earlier been performed in 22 of these patients. No phenotypic aberrations were detected in the patient group. 8 patients had the HLA-B12 phenotype. Lymphocytes from the HLA-B12 phenotype stimulated with a lymphocyte mitogen have earlier been shown to react with decreased inhibitory effect to histamine. 2 patients in this study had the HLA-B12 phenotype and systemic mastocytosis with high histamine turnover, but these patients reacted with a low mitogen response of the lymphocytes.

Response of cutaneous mast cells to PUVA in patients with urticaria pigmentosa: histomorphometric, ultrastructural, and biochemical investigations

In six patients with urticaria pigmentosa, population density and ultrastructure of the cutaneous mast cells and histamine levels of the lesional skin were studied before, immediately after, and again 5-8 months after photochemotherapy (PUVA). Immediately after PUVA, the total mast cell number was not reduced, but on separate analysis of the intradermal distribution, significantly fewer mast cells were found in the papillary dermis and correspondingly more mast cells in the adjacent upper dermis. On electron microscopic examination, 4% of the mast cell granules were immature before and 27% after PUVA therapy, based on the lower electron density of the granular matrix. This was associated with a markedly lower histamine content of the lesional skin. Five to eight months after recovery from PUVA, the morphologic changes and the histamine levels had all returned to the pre-PUVA status. These findings were paralleled by a reversal of all clinical beneficial effects that had been observed with PUVA.

Immunohistochemical characterization of reactive and neoplastic mast cells

Mast cells are connective tissue elements likened to unicellular endocrine organs because of the wide diversity of physiologic and pathologic events associated with the secretion of biologically active compounds. Using an immunoperoxidase method (PAP), we studied tissue from patients with benign and malignant systemic mastocytosis and with a variety of reactive conditions. The following immunoreactive antigens were identified in mast cells: a heparinlike compound or compounds (HLC), prostaglandin, serotonin, and fibronectin. HLC is constantly present, staining mast cells in a granular fashion from most lesions. Serotonin and prostaglandin stain in a diffuse cytoplasmic manner in occasional lesions. Fibronectin is found in a surface location in selected cases. We found no clear association between the immunoreactivity of one compound in mast cells and one clinical symptom, e.g., HCL with bleeding, prostaglandin, or serotonin with systemic vasomotor activity or fibronectin with increased tissue fibrosis. However, patients with localized and systemic disease had symptoms that might have been attributed to more than one compound. Only occasional patients with reactive conditions showed such symptoms. The presence of these compounds, either alone or in combination, did not separate benign from malignant conditions. Other cells within selected tissues also stained with the antibodies tested. Despite the lack of exclusivity, these antibodies are useful in identifying mast cells within tissue sections and may have a role in the study of mast cell constituents.

Photochemotherapy (PUVA) in the treatment of urticaria pigmentosa

Eight patients received PUVA for mastocytosis. Five women had typical adult-onset urticaria pigmentosa, without evidence of systemic disease. Another woman had suspected hepatic involvement while the remaining female had early-onset familial urticaria pigmentosa with morphologically atypical mast cells. The only male patient had cirrhosis with hepatic deposits of mast cells in addition to polycythaemia rubra vera. In all patients, except the man with systemic disease, there was reduced pruritus and wealing and partial to almost complete fading of the macules. The manifestations of urticaria pigmentosa recurred after treatment was discontinued. In both lesional and uninvolved skin there was no significant change in either the mean mast cell counts or mast cell ultrastructure after an average of twenty-seven PUVA exposures. In addition, PUVA did not cause a significant alteration in the histamine content of the skin. The beneficial effect of PUVA in urticaria pigmentosa therefore does not appear to be directly related to a change in mast cell numbers or morphology, or to the histamine concentration in the skin.

Studies on histamine metabolism in mastocytosis

The urinary excretion of histamine and its main metabolite, 1-methyl-4-imidazoleacetic acid (MeImAA), was determined in 30 adult patients with the clinical diagnosis of urticaria pigmentosa (UP). Clinical and laboratory investigations including skin histology, bone marrow examination, and scintigraphy of the skeleton, liver, and spleen revealed systemic manifestations in 14 cases. Among the 16 cases with dermal proliferation of mast cells only 3 cases classified as telangiectasia macularis eruptiva perstans (TMEP). All patients with systemic mastocytosis and UP excreted increased amounts of MeImAA in the urine while normal amounts were found in 2 of the patients with TMEP. A significant correlation existed between MeImAA excretion and the extent of mast cell infiltration in skin and internal organs. No such correlation was found for urinary histamine. Urinary MeImAA but not histamine is therefore considered a useful indicator of systemic involvement by reflecting the size of the mast cell histamine pool. The main symptom of the patients was pruritus, which was moderate to severe in 17 and mild or absent in 13 cases. Gastrointestinal symptoms were present in 14 patients. However, there was no obvious correlation between the excretion of MeImAA and any of the symptoms recorded. Neither was the severity of pruritus correlated to the histamine content of the skin, which was measured in both lesional and unaffected skin in 23 of the patients. Thus, symptoms possibly caused by histamine in mastocytosis patients are not directly related to urinary histamine metabolite excretion or tissue histamine content.

Long-term treatment of systemic mastocytosis with histamine H2 receptor antagonists

A patient with systemic mastocytosis, accompanied by gastric hypersecretion and duodenal ulcer, was treated with metiamide followed by daily cimetidine for 44 months. Treatment with cimetidine resulted in healing of the ulcer, without recurrence and marked amelioration of the cutaneous symptoms of mastocytosis. Complete suppression of basal gastric hypersecretion was documented after 33 months of treatment and cimetidine and Vitamin B12 absorption remained normal. Cimetidine reduced the patient's cutaneous response to intradermal histamine without affecting leucocyte histamine release. No cimetidine toxicity was observed. These results indicate that effective long-term control of histamine-induced gastric hypersecretion can be achieved with cimetidine. They suggest that some of the cutaneous symptoms of mastocytosis are mediated via histamine H2 receptors in the skin.

Calcification of cultured urticaria pigmentosa skin. An electron optical study of the calcium-apatite deposition

Mast cells participate in experimental calcinosis. Skin from patients with urticaria pigmentosa (cutaneous mastocytosis) calcifies in vitro. In the present report, the nature of the calcium deposit was studied by electron optical techniques. The cultured mast cells of urticaria pigmentosa skin were surrounded by a large number of round bodies with an average diameter of 200-300 nm. Most of the round bodies were membrane bounded, while a few contained lamellar structures. These bodies may represent matrix vesicles as seen in calcifying hard tissues and/or may be remnants of mast cell granules. The calcified deposits were located on the round bodies, collagen fibrils and elastic matrix. Electron diffraction and X-ray microanalysis demonstrated that the deposits consisted of crystalline calcium apatite.

Systemic mastocytosis and the mastocytosis syndrome

A patient with extensive systemic mastocytosis and the mastocytosis syndrome was studied by light and electron microscopy. Mast cell proliferation was found in the bone marrow, the liver, spleen and lymph node. In addition, the patient had telangiectasia macularis eruptiva perstans and elevated histamine levels.

Blood and urine histamine levels in normal and pathological states as measured by a radiochemical assay

The utility of the enzymatic radiochemical assay of histamine in diagnosing diseases with known abnormalities in histamine production was investigated. Whole blood histamine levels were abnormal only in patients with basophilia, i.e. chronic myelocytic leukemia or polycythemia vera. Histamine was not detectable (less than 1 ng/ml) in normal plasma but was detected in plasma of some patients witheither mastocytosis or chronic myelocytic leukemia. These patients also had symptoms which could be attributed to histamine release as, for example, hyperchlorhydria and hypotension. Urinary histamine excretion was also abnormally high in these diseases compared to normal subjects (range less than 5-42 microgram/24 h, n = 31). Patients with systemic mastocytosis had higher urine values (greater than 150 microgram/24 h) than those with cutaneous mastocytosis (39-88 microgram/24 h), and the urinary histamine excretion appeared to be an index of the severity of the diseases. Studies with L-histidine loading suggest that the kidney is one possible source of urinary histamine.

Histochemical demonstration of hyaluronic acid in human dermal mast cells

Acid mucopolysaccharides in mast cell granules were histochemically studied in the lesion of urticaria pigmentosa and in the dermis of normal human skin. Alcian blue and azure A were used to stain mucopolysaccharides. Bromphenol blue was employed for detection of basic proteins. In a further attempt to identify various polyanions, staining was carried out with alcian blue containing various concentrations of electrolytes. Methylation, saponification, and digestion with streptomyces or testicular hyaluronidase, chondroitinase ABC, sialidase, or desoxyribonuclease were also employed. The results obtained are most likely to suggest the presence of hyaluronic acid in mast cell granules.

Histamine release from skin mast cells and basophils in patients with urticaria pigmentosa

Histamine release from dispersed skin mast cells may be used for functional studies on the mast cell. However, technical difficulties have hampered such studies. In the present study a new fiberglass-based histamine assay was applied to previously described dispersion techniques, using excision biopsies from 7 patients with urticaria pigmentosa, 3 with psoriasis as well as 4 with urticaria. However, sufficient mast cell numbers for performing histamine release could only be obtained from patients with urticaria pigmentosa. The average mast cell yield was 935 +/- 470 cells (mean +/- SD) per mg wet weight of tissue. The skin mast cells from these patients responded with dose-dependent histamine release to anti-IgE, calcium ionophore A23187, and N-formyl-methionyl-leucyl-phenylalanine challenge without previous passive sensitization. The pattern of histamine release of mast cells and corresponding blood basophils did not indicate substantial differences between the two cell types.