Secretion in dissociated human pulmonary mast cells. Evidence for solubilization of granule contents before discharge

The development of methods for primary mast cells in vitro and ex vivo: An historical review

Mast cells (MCs) are tissue-based stationary effector cells that form the immune system's first-line defense against various challenges. They are developed from the bone marrow-derived progenitors to complete their differentiation and maturation in the tissues where they eventually establish residence. MCs have been implicated in many diseases, such as allergy, parasitic infection, and neoplastic disorders. Immortalized MC lines, such as RBL-2H3, HMC-1, and LAD-2, are useful for investigating the biological functions of MC only to some extents due to the restriction of degranulation evaluation, in vivo injection and other factors. Over the past few decades, technologies for acquiring primarily MCs have been continually optimized, and novel protocols have been proposed. However, no relevant publications have analyzed and summarized these techniques. In this review, the classical approaches for extracting MCs are generalized, and new methods with potential values are introduced. We also evaluate the advantages and applicability of diverse MC models. Since MCs exhibit substantial plasticity and functional diversity due to different origins, it is both necessary and urgent to select a reliable and suitable source of MCs for a particular study.

Mast cells partially contribute to mucosal adjuvanticity of surfactin in mice

Introduction

Surfactin (SF) is a cyclic lipopeptide that has potent mucosal adjuvant properties. However, immunological mechanisms of SF adjuvant action have not yet been elucidated. As some cyclic lipopeptides, such as polymyxin, can stimulate histamine release from mast cells, we hypothesized that mast cell activation is critical for SF adjuvanticity.

Methods/Results

We observed that following intranasal immunization with ovalbumin (OVA) plus SF, the titers of the OVA‐specific antibody (Ab) in the mucosal secretions and plasma of mast cell‐deficient mice were significantly lower than those in congenic normal mice, although OVA‐specific Ab did not entirely disappear from mast cell‐deficient mice. SF induced degranulation of mast cells and release of histamine in vitro. To investigate whether SF stimulated mast cells in vivo, we measured body temperature of mice immunized intranasally with OVA plus SF because histamine level affects body temperature. Following immunizations, body temperature of immunized congenic normal mice transiently decreased, whereas body temperature of mast cell‐deficient mice did not change. Plasma levels of OVA‐specific IgE Ab were not significantly different in mast cell‐deficient and congenic normal mice. These findings suggest that SF directly affected mast cells in an IgE Ab‐independent fashion. Furthermore, we analyzed the effects of SF on MC/9 mast cells cultured in vitro. MC/9 cells stimulated by SF released not only histamine but also leukotriene B₄ and prostaglandin D₂. Moreover, SF up‐regulated mRNA expression levels of Tnf, Ccr5, and Il4 genes in mast cells. These cytokines may play a facilitating role in OVA‐specific immune responses in mice.

Conclusion

Overall, our results showed that mast cell activation partially mediated SF adjuvanticity.

Mast cells in asthma--state of the art

Mast cells (MCs) play a central role in tissue homoeostasis, sensing the local environment through numerous innate cell surface receptors. This enables them to respond rapidly to perceived tissue insults with a view to initiating a co-ordinated programme of inflammation and repair. However, when the tissue insult is chronic, the ongoing release of multiple pro-inflammatory mediators, proteases, cytokines and chemokines leads to tissue damage and remodelling. In asthma, there is strong evidence of ongoing MC activation, and their mediators and cell-cell signals are capable of regulating many facets of asthma pathophysiology. This article reviews the evidence behind this.

Inhibition of TRPM7 channels reduces degranulation and release of cytokines in rat bone marrow-derived mast cells

Background: mast cells play an important role in airway inflammation in asthma. The transient receptor potential melastatin-like 7 (TRPM7) channel is expressed in primary human lung mast cells and plays a critical role for cell survival. This study aimed to investigate the role of TRPM7 on degranulation and release of cytokines in rat bone marrow-derived mast cells (BMMCs). Methods: the expression levels of TRPM7 were observed by immunocytochemistry and RT-PCR between normal and asthmatic rat BMMCs. TRPM7-specific shRNA and 2-aminoethoxydiphenyl borate (2-APB) and specific shTRPM7 were used to inhibit the function of TRPM7. Degranulation levels were analyzed by beta-hexosaminidase assay. Histamine, TNF-α, IL-6 and IL-13 levels were measured by ELISA. Results: the expression of TRPM7 was significantly higher in asthmatic rat BMMCs than in the normal control group. After application of 2-APB and down-regulation of TRPM7, the beta-hexosaminidase activity and secretion of histamine, IL-6, IL-13 and TNF-α were significantly decreased in the asthmatic group compared to the control group. Conclusion: this study indicates that TRPM7 channels may be involved in the process of degranulation and release of cytokines in rat bone marrow-derived mast cells.

Homoisoflavanone prevents mast cell activation and allergic responses by inhibition of Syk signaling pathway

BACKGROUND

Mast cells play important roles in allergic inflammatory responses because they produce leukotrienes (LTs), prostaglandins (PGs), and a variety of inflammatory cytokines. Thus, pharmacological interventions for allergies have focused on inhibiting mast cell activation. Homoisoflavanone (HIF), isolated from Cremastra appendiculata Makino, has anti-angiogenic activities; however, its effects on allergic reactions have not been determined. The aim of this study was to assess the inhibitory effects of HIF on mast cell activation, which is critical for anti-allergic reaction and the underlying mechanisms.

METHODS

Enzyme-linked immunosorbent assays, quantitative real-time PCR, western blot analyses, and degranulation assay were performed to measure pro-inflammatory and allergic mediators in PMA/A23187- or IgE/antigen-stimulated mouse bone marrow-derived mast cells (BMMCs), HMC-1, RBL-1, or human PBMC-derived mast cells treated with or without HIF. The anti-allergic effects of HIF were determined in mouse models using dinitrophenol-immunoglobulin E-induced passive cutaneous anaphylaxis (PCA) and compound 48/80-induced ear swelling.

RESULTS

Homoisoflavanone down-regulated PGD2 , LTB4 , and LTC4 production and inhibited the production of pro-inflammatory cytokines, such as interleukin-6 and tumor necrosis factor-α in PMA/A23187- or IgE/antigen-stimulated mast cells. The molecular mechanisms by which HIF caused these inhibitory effects were determined to be the inactivation of spleen tyrosine kinase (Syk) signaling and the concurrent suppression of cPLA2 . HIF inhibited IgE-mediated PCA and compound 48/80-induced ear swelling in mouse.

CONCLUSIONS

Homoisoflavanone inhibited mast cell activation through the suppression of Syk pathway together with the inhibition of cPLA2 . Thus, it might be a good candidate molecule for allergic diseases.

Ultrastructural characteristics of molecular release of secretory products from thyroid mast cells induced by lipopolysaccharide

Ultrastructural characteristics of molecular release of secretory products from thyroid mast cells during different periods after LPS injection were studied in rats. The main morphological manifestation of this mechanism was progressing hydration of the hyaloplasm around secretory granules and dissolution and release of osmiophilic contents from the granules to the cytoplasm with the formation of a hydropic vacuole at the site of the granule.

Analysis of colonic mucosa mast cell count in patients with chronic diarrhea

BACKGROUND/AIM

Chronic diarrhea is defined as a decrease in fecal consistency lasting for four or more weeks. Prevalence of this complication in the general population is 5%. Mast cells that play an important role in the regulation of gastrointestinal visceral sensitivity and vascular permeability may be involved in functional chronic diarrhea. In this study we tried to evaluate mast cells density in colonic mucosa of patients with chronic diarrhea.

PATIENTS AND METHODS

50 patients with chronic diarrhea and 50 persons as control group were investigated. All specimens were immunohistochemically stained for mast cell tryptase (MCT) with monoclonal mouse anti-human MCT as well as toluidine blue. Mean number of mucosal mast cells were counted in 10 high power microscopic fields of patients and control groups.

RESULTS

In patients group (age range, 15-78 years; 26 females), the number of mast cells per high power field in the immunohistochemistry staining was 21.3 ± 4.8 compared to 14.2 ± 3.4 in the control group (age range, 18-78 years; 24 females) [P < 0.001]. Also number of mast cells in toluidine blue staining was 10.3 ± 3.6 per high power field in cases and 7.1 ± 2.4 in the control group (P < 0.001).

CONCLUSION

Elevated number of colonic mast cells exist in patients with chronic diarrhea. Further research should be considered on application of these findings for new therapeutic opportunities.

The mast cell in innate and adaptive immunity

Mast cells (MCs) were once considered only as effector cells in pathogenic IgE- and IgG-mediated responses such as allergy. However, developments over the last 15 years have suggested that MCs have evolved in vertebrates as beneficial effector cells that are involved in the very first inflammatory responses generated during infection. This pro-inflammatory environment has been demonstrated to be important for initiating innate responses in many different models of infection and more recently, in the development of adaptive immunity as well. Interestingly this latter finding has led to the discovery that small MC-activating compounds can behave as adjuvants in vaccine formulations. Thus, our continued understanding of the MC in the context of infectious disease is likely to not only expand our scope of the MC in the normal processes of immunity, but provide new therapeutic targets to combat disease.

Functional Expression of TRPV4 Cation Channels in Human Mast Cell Line (HMC-1)

Mast cells are activated by specific allergens and also by various nonspecific stimuli, which might induce physical urticaria. This study investigated the functional expression of temperature sensitive transient receptor potential vanilloid (TRPV) subfamily in the human mast cell line (HMC-1) using whole-cell patch clamp techniques. The temperature of perfusate was raised from room temperature (RT, 23~25℃ to a moderately high temperature (MHT, 37~39℃ to activate TRPV3/4, a high temperature (HT, 44~46℃ to activate TRPV1, or a very high temperature (VHT, 53~55℃ to activate TRPV2. The membrane conductance of HMC-1 was increased by MHT and HT in about 50% (21 of 40) of the tested cells, and the I/V curves showed weak outward rectification. VHT-induced current was 10-fold larger than those induced by MHT and HT. The application of the TRPV4 activator 4α-phorbol 12,13-didecanoate (4αPDD, 1µM) induced weakly outward rectifying currents similar to those induced by MHT. However, the TRPV3 agonist camphor or TRPV1 agonist capsaicin had no effect. RT-PCR analysis of HMC-1 demonstrated the expression of TRPV4 as well as potent expression of TRPV2. The [Ca(2+)](c) of HMC-1 cells was also increased by MHT or by 4αPDD. In summary, our present study indicates that HMC-1 cells express Ca(2+)-permeable TRPV4 channels in addition to the previously reported expression of TRPV2 with a higher threshold of activating temperature.

TRPM8 mediates cold and menthol allergies associated with mast cell activation

Exposure to low temperatures often causes allergic responses or urticaria. Similarly, menthol, a common food additive is also known to cause urticaria, asthma, and rhinitis. However, despite the obvious clinical implications, the molecular mechanisms responsible for inducing allergic responses to low temperatures and menthol have not been determined. Because a non-selective cation channel, transient receptor potential subtype M8 (TRPM8) is activated by cold and menthol, we hypothesized that this channel mediates cold- and menthol-induced histamine release in mast cells. Here, we report that TRPM8 is expressed in the basophilic leukemia mast cell line, RBL-2H3, and that exposure to menthol or low temperatures induced Ca(2+) influx in RBL-2H3 cells, which was reversed by a TRPM8 blocker. Furthermore, menthol, a TRPM8 agonist, induced the dose-dependent release of histamine from RBL-2H3 cells. When TRPM8 transcripts were reduced by siRNA (small interfering RNA), menthol- and cold-induced Ca(2+) influx and histamine release were significantly reduced. In addition, subcutaneous injection of menthol evoked scratching, a typical histamine-induced response which was reversed by a TRPM8 blocker. Thus, our findings indicate that TRPM8 mediates the menthol- and cold-induced allergic responses of mast cells, and suggest that TRPM8 antagonists be viewed as potential treatments for cold- and menthol-induced allergies.

Single-channel properties of a stretch-sensitive chloride channel in the human mast cell line HMC-1

A stretch-activated (SA) Cl(-) channel in the plasma membrane of the human mast cell line HMC-1 was identified in outside-out patch-clamp experiments. SA currents, induced by pressure applied to the pipette, exhibited voltage dependence with strong outward rectification (55.1 pS at +100 mV and an about tenfold lower conductance at -100 mV). The probability of the SA channel being open (P (o)) also showed steep outward rectification and pressure dependence. The open-time distribution was fitted with three components with time constants of tau(1o) = 755.1 ms, tau(2o) = 166.4 ms, and tau(3o) = 16.5 ms at +60 mV. The closed-time distribution also required three components with time constants of tau(1c) = 661.6 ms, tau(2c) = 253.2 ms, and tau(3c) = 5.6 ms at +60 mV. Lowering extracellular Cl(-) concentration reduced the conductance, shifted the reversal potential toward chloride reversal potential, and decreased the P (o) at positive potentials. The SA Cl(-) currents were reversibly blocked by the chloride channel blocker 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) but not by (Z)-1-(p-dimethylaminoethoxyphenyl)-1,2-diphenyl-1-butene (tamoxifen). Furthermore, in HMC-1 cells swelling due to osmotic stress, DIDS could inhibit the increase in intracellular [Ca(2+)] and degranulation. We conclude that in the HMC-1 cell line, the SA outward currents are mediated by Cl(-) influx. The SA Cl(-) channel might contribute to mast cell degranulation caused by mechanical stimuli or accelerate membrane fusion during the degranulation process.

Time course of human conjunctival mast cell degranulation in response to compound 48/80

Compound 48/80, a non-immunogenic mast cell degranulatory agent, is known to produce the signs and symptoms of ocular allergy. Maximal mast cell degranulation of human conjunctiva occurred within the first hour after stimulation by a single topical dose of compound 48/80 (20 microliters, 7.5 mg/ml). The average percentage of fully degranulated mast cells in treated specimens (n = 9) was 31% (range 5-60%) versus 6% (range 0-20%) in control specimens (n = 5). Exact correlates of representative granulated, partially degranulated, and fully degranulated mast cells were determined by light and transmission electron microscopy.

Experimental activation of mast cells and their pharmacological modulation

The activation of mast cells is of pivotal importance in the pathogenesis of allergic conditions. Mast cell activation can provoke rapid increases in microvascular permeability, induce bronchoconstriction after blood flow, stimulate the recruitment and activation of other inflammatory cells, and has come to be associated with the processes of tissue remodeling and fibrosis. Such changes may be mediated by the release of a range of potent mediators of inflammation: preformed in secretory granules, or newly generated, or both. There are major differences in the responsiveness to various stimuli and to pharmacological agents for mast cells from different body compartments. A method is presented here for the purification of mast cells from enzymatically dispersed human tissues. The methods described for the experimental activation of mast cells can be readily adapted to studies with cell lines or mast cells obtained through long-term culture.

Ultrastructure of anterior uterus of the oviduct and the stored sperm in female soft-shelled turtle, Trionyx sinensis

Ultrastructure of sperm storage in female soft-shelled turtle, Trionyx sinensis was examined under light and electron microscopes. Sperm storage tubules are restricted to the anterior of the uterus. These tubules developed either by folding or fusion of the oviductal mucosal folds and are lined by both ciliated and secretory cells. Ciliated cells are characterized by a few microvilli and prominent cilia in the apical membranes. A prominent feature of the secretory cell is the presence of secretory granules in the supranuclear region. The size, shape, and electron density of these granules vary markedly. The secretory product is released mainly by exocytosis into the oviductal lumen, where it appears as flocculent material. The unique structure in the base of the epithelium, the basal border of the cell -- the basal lamina -- and a blood vessel layer, is presumed to be a important barrier, by which the nourishment exchange and the microenvironment maintenance are ensured. The gland cell is presented with numerous, round, membrane-bound secretory granules of moderate to high electron densities. We divide these granules into three types according to their appearance: (1) membrane bounded granules with high-homogeneous electron density, (2) membrane bounded granules with moderate-homogeneous electron density, (3) membrane bounded, electron dense granules with concentric structures. These granules are presented as different stages of the secretions in the gland cell. The junction complexes are markedly distributed between cells, which are important in keeping stability and the microenvironment maintenance of the sperm storage tubules. Sperm stored in the tubules are heterogeneous in cytology. In addition to the mature sperm in the lumen, sperm with large chromatic granules are found, which are presumed to be immature sperm and are being in the process of nuclear condensation. Several spermatozoa in the tubules are exhibited with definitive indications of degeneration of the nuclei. The nuclear volume increases. The electron density of the central cores in mitochondria declines, combined with the deterioration of concentric membrane structure. Those changes are possibly due to the long time storage of the sperm in sperm storage tubules, and the leakage of reactive oxygen species is suggested to be a major cause. We conclude that the ultrastructure character of sperm storage in the oviduct of Trionyx sinensis is unique, in addition to having a basal function in secretion and the cilia swing, the tubules also provide an available microenvironment for the sperm to long time stored. The degenerative sperm in the tubules might be related to paternity-specific reproductive adaptations, and the sperm competition might occur during long time storage.

Doing What I Like

I have spent my entire professional life at Harvard Medical School, beginning as a medical student. I have enjoyed each day of a diverse career in four medical subspecialties while following the same triad of preclinical areas of investigation—cysteinyl leukotrienes, mast cells, and complement—with occasional translational opportunities. I did not envision a career with a predominant preclinical component. Such a path simply evolved because I chose instinctively at multiple junctures to follow what proved to be propitious opportunities. My commentary notes some of the highlights for each area of interest and the mentors, collaborators, and trainees whose counsel has been immensely important at particular intervals or over an extended period.

Urticaria Neonatorum: accumulation of tryptase-expressing mast cells in the skin lesions of newborns with Erythema Toxicum

Erythema Toxicum, a rash frequently present in the healthy newborn infant is an innate, immune response to the first commensal micro flora. Flushing and urtication are seen in this manifestation suggesting mast cell (MC) activation and MC derived mediator release. It has recently become evident that MCs participate in the protective, innate immune response against microbes also by secreting products toxic to pathogens such as cathelicidin peptide antibiotics. We hypothesized that MCs contribute to the process of inflammation in Erythema Toxicum and that skin MCs of human newborns express the cathelicidin peptide antibiotic LL-37. Skin sections were immunostained for MC tryptase. Double immunofluorescence was performed by staining LL-37 in combination with tryptase. We studied ultra structure of skin MCs with transmission (TEM) and immunoelectron microscopy (IEM). Seven infants with and six infants without the rash, as well as three adults were included. We found numerous tryptase-expressing MCs recruited around the hair follicles in the lesions of Erythema Toxicum. TEM analysis of MCs exhibited signs of degranulation in the lesion. Neither skin MCs from newborns nor adults did express LL-37 as judged by confocal and IEM. MCs participate in the inflammatory responses of Erythema Toxicum by taking an active part in the immune system of the hair follicle. However, their immunological activity is not linked to the expression of the cathelicidin antimicrobial peptide LL-37. A pivotal role of MCs in the innate, inflammatory response at the site of pathogen invasion during the critical time of perinatal colonization is suggested.

Functional transient receptor potential melastatin 7 channels are critical for human mast cell survival

Mast cells play a significant role in the pathophysiology of many diverse diseases such as asthma and pulmonary fibrosis. Ca2+ influx is essential for mast cell degranulation and release of proinflammatory mediators, while Mg2+ plays an important role in cellular homeostasis. The channels supporting divalent cation influx in human mast cells have not been identified, but candidate channels include the transient receptor potential melastatin (TRPM) family. In this study, we have investigated TRPM7 expression and function in primary human lung mast cells (HLMCs) and in the human mast cell lines LAD2 and HMC-1, using RT-PCR, patch clamp electrophysiology, and RNA interference. Whole cell voltage-clamp recordings revealed a nonselective cation current that activated spontaneously following loss of intracellular Mg2+. The current had a nonlinear current-voltage relationship with the characteristic steep outward rectification associated with TRPM7 channels. Reducing external divalent concentration from 3 to 0.3 mM dramatically increased the size of the outward current, whereas the current was markedly inhibited by elevated intracellular Mg2+ (6 mM). Ion substitution experiments revealed cation selectivity and Ca2+ permeability. RT-PCR confirmed the presence of mRNA for TRPM7 in HLMC, LAD2, and HMC-1 cells. Adenoviral-mediated knockdown of TRPM7 in HLMC with short hairpin RNA and in HMC-1 with short interfering RNA markedly reduced TRPM7 currents and induced cell death, an effect that was not rescued by raising extracellular Mg2+. In summary, HLMC and human mast cell lines express the nonselective cation channel TRPM7 whose presence is essential for cell survival.

Nasal Polyps

Nasal polyps are grossly oedematous tissue which has undergone considerable shrinkage when processed for scanning electron microscopy (SEM), converting the normally smooth surface into one with undulations. This shrinkage resulted in variable degrees of loss of the surface epithelium and thus gave rise to artifact. In its severest form, the entire surface epithelium was removed and the basement membrane exposed; lesser damage resulted in exposure of the basal cells, giving the previously described ‘cobblestone’ appearance. When the epithelium was intact, it was typical respiratory in type.

Key role of mast cells and their major secretory products in inflammatory bowel disease

Historically, mast cells were known as a key cell type involved in type I hypersensitivity. Until last two decades, this cell type was recognized to be widely involved in a number of non-allergic diseases including inflammatory bowel disease (IBD). Markedly increased numbers of mast cells were observed in the mucosa of the ileum and colon of patients with IBD, which was accompanied by great changes of the content in mast cells such as dramatically increased expression of TNF-α, IL-16 and substance P. The evidence of mast cell degranulation was found in the wall of intestine from patients with IBD with immunohistochemistry technique. The highly elevated histamine and tryptase levels were detected in mucosa of patients with IBD, strongly suggesting that mast cell degranulation is involved in the pathogenesis of IBD. However, little is known of the actions of histamine, tryptase, chymase and carboxypeptidase in IBD. Over the last decade, heparin has been used to treat IBD in clinical practice. The low molecular weight heparin (LMWH) was effective as adjuvant therapy, and the patients showed good clinical and laboratory response with no serious adverse effects. The roles of PGD2, LTC4, PAF and mast cell cytokines in IBD were also discussed. Recently, a series of experiments with dispersed colon mast cells suggested there should be at least two pathways in man for mast cells to amplify their own activation-degranulation signals in an autocrine or paracrine manner. The hypothesis is that mast cell secretogogues induce mast cell degranulation, release histamine, then stimulate the adjacent mast cells or positively feedback to further stimulate its host mast cells through H₁ receptor. Whereas released tryptase acts similarly to histamine, but activates mast cells through its receptor PAR-2. The connections between current anti-IBD therapies or potential therapies for IBD with mast cells were discussed, implicating further that mast cell is a key cell type that is involved in the pathogenesis of IBD. In conclusion, while pathogenesis of IBD remains unclear, the key role of mast cells in this group of diseases demonstrated in the current review implicates strongly that IBD is a mast cell associated disease. Therefore, close attentions should be paid to the role of mast cells in IBD.

CC chemokine receptor 3 mobilizes to the surface of human mast cells and potentiates immunoglobulin E-dependent generation of interleukin 13

Eotaxins-1, -2, and -3 mediate the recruitment of blood-borne eosinophils to allergically inflamed tissues by binding CC chemokine receptor (CCR) 3. Mast cells (MCs) are resident tissue cells that also express CCR3. In the present study, we demonstrate that human (h) MCs in nasal polyps and cultured cord blood-derived hMCs express CCR3 not only on their surfaces but also in their secretory granules. Activation of hMCs mediated by the high-affinity Fc receptor for immunoglobulin (Ig)E (Fc epsilon RI) increased the surface presentation of CCR3 within 1 h, with a parallel decrease in intracellular CCR3 as determined by flow cytometry on saponin-permeabilized hMCs. Recombinant eotaxin-1 alone did not induce histamine release or cytokine generation, and did not significantly augment IgE-dependent histamine release by interleukin (IL)-4-primed hMCs. Nevertheless, stimulation of hMCs with eotaxin-1 2 h after Fc epsilon RI cross-linkage (concomitantly with maximal surface CCR3 expression) increased Fc epsilon RI-dependent IL-13 generation by hMCs, compared with their replicates stimulated simultaneously with both agonists. Thus, hMCs may store CCR3 and rapidly mobilize it to their surface with IgE-dependent activation, providing a novel potential mechanism for enhanced hMC effector function, including IL-13 production.

Effects of rhinovirus infection on histamine and cytokine production by cell lines from human mast cells and basophils

To understand the biochemical events that occur in the airways after rhinovirus (RV) infection, we developed for the first time a model in which the cell lines from human mast cells (HMC-1) and basophils (KU812) can be infected with RV14, a major group RV. Viral infection was confirmed by demonstrating that viral titers in culture supernatants, and RV RNA increased with time. RV14 infection alone and a combination of PMA plus calcium ionophore A23187, did not increase histamine production by these cells, although IgE plus anti-IgE increased the histamine production. However, histamine content in the supernatants increased in response to PMA plus A23187, or IgE plus anti-IgE after RV14 infection. PMA plus A23187 or IgE plus anti-IgE induced the production of IL-8 and GM-CSF in supernatants of HMC-1 cells and IL-4 and IL-6 in supernatants of KU812 cells. RV14 infection further increased the production of the cytokines, whereas RV14 infection alone did not alter the production of the cytokines by these cells. An Ab to ICAM-1 inhibited RV14 infection of the cells and decreased the production of cytokines and histamine after RV14 infection. RV14 infection enhanced the increases in intracellular calcium concentration and activation of NF-kappaB by PMA plus A23187 in the cells. These findings suggest that RV14 infection may prime the cytokine and histamine production from mast cells and basophils and may cause airway inflammation in asthma.

The structure of mast cell secretory granules in the blind mole rat (Spalax ehrenbergi)

Eosinophils, basophils, and mast cells produce and secrete active substances whose role is to attack invading parasites and protect the host. In this study we use morphometric methods to study mast cells in the blind mole rat (Spalax ehrenbergi). The subterranean and solitary way of life of this species has led to the evolutionary development of special anatomical, morphological, behavioral, and physiological adaptations. Because of its particular lifestyle, the mole rat is less exposed to parasites than other rodents. This could provide a unique model for research into the pathobiology of mast cells. The paracrystalline structure of the mast cell granule content is composed of parallel plates. Diffraction analysis of electron micrographs of thin sections of araldite-embedded tissues indicated that each crystal line plate is a periodic array of parallelograms. The crystal unit cell volume is approximately 930 nm(3), suggesting that each unit cell is composed of one heparin molecule and one to three additional adsorbed proteins. Morphometric data show that characteristics of the secretory granules of mast cells of the blind mole rat resemble those of other rodents. The mast cell unit granule volume in the present study was calculated to be 0.055 microm(3), similar to that of rat peritoneal mast cells.

Intracellular localization of serotonin in mast cells of the colon in normal and colitis rats

Intracellular localization of serotonin (5-HT) in the mast cells of two phenotypes in normal rat colon and dextran sodium sulphate-induced colitis was studied by immunoelectron microscopy with a quantitative analysis of the distribution of immunogold labelling. Mucosal mast cells in normal rats contained round shape secretory granules with varying electron density. Immunogold labelling for 5-HT was concentrated over the secretory granules. In mucosal mast cells from colitis rats, vacuolated granules without 5-HT labelling were frequently observed and immunogold labelling over the secretory granules was significantly increased compared to controls. On the other hand, connective tissue mast cells in normal rats contained oval shape secretory granules with homogeneous electron density. Their immunogold labelling was diffusely scattered over the secretory granules as well as over the cytoplasm. In connective tissue mast cells from colitis rats, secretory granules with high electron density were increased and the immunogold labelling over the secretory granules was much higher than that in controls. The present results suggest that intracellular localization of 5-HT is different in two phenotypes of mast cells and they may release 5-HT in a different manner. Mucosal mast cells may release 5-HT by a degranulation or exocytosis, while connective tissue mast cells may release 5-HT by a diacrine manner of secretion.

Activation and inhibition of mast cells degranulation affect their morphometric parameters

Activation of mast cells, the key cells of allergic inflammation, causes typical morphological changes associated with an increase in volume, that is a function of area and perimeter. The purpose of this study was to evaluate the effect of mast cell activation to degranulate, carried out by the secretagogue Compound 48/80, and of inhibition of this activation carried out by Nedocromil sodium, a mast cell stabilizing drug, on mast cell area, perimeter and shape factor by a computerized image analyzer. Mast cells were isolated and purified by peritoneal lavage of rats (purity >98%) and co-cultured with mouse 3T3 fibroblasts to which they adhere. Cultures were incubated for 10 min at 37 degrees C with culture medium alone (Enriched Medium) or Enriched Medium containing either Nedocromil (10(-4) M) or Compound 48/80 (0.3 microg/ml) or Compound 48/80 and Nedocromil (0.3 microg/ml and 10(-4) M respectively). Supernatants were then assessed for histamine release, as a marker of mast cell activation and the cell monolayers were fixed and stained with an alcoholic-acidic toluidine blue solution and examined with a computerized image analyzer connected with a light microscope. Mast cells incubated in Enriched Medium or Nedocromil possessed similar morphometric parameters. Mast cells activated with Compound 48/80 (70% histamine release) had a significant increase in area and perimeter and a decrease in shape factor in comparison to mast cells in Enriched Medium alone. Simultaneous incubation of mast cells with Compound 48/80 and Nedocromil significantly inhibited their histamine release (36% histamine release) and the increase in area and perimeter, but did not affect significantly their shape factor, in comparison with mast cells incubated with Compound 48/80 alone. These data clearly show that there is a relationship between mast cell activation, consequent histamine release and changes in cell area, perimeter and shape factor and that Nedocromil not only inhibits mast cell histamine release but also the activation induced morphometric changes in mast cells.

Allergenic activity of a major grass pollen allergen is elevated in the presence of nasal secretion

Phl p5 is a major allergen of timothy grass and causes rhinitis and bronchial asthma in nearly all patients allergic to grass pollen. The biochemical processing of this molecule by the nasal mucosa at its first encounter and possible changes of its biologic activity are unknown. Two isoforms of the allergen were expressed in Escherichia coli and subsequently purified. Conversion of these preparations to various forms with molecular size between 10 and 20 kD in the presence of nasal secretion was observed. Surprisingly, in skin prick test assays with allergic patients the mixture of converted peptides caused significantly higher allergic response when compared with the parent protein. Allergenic activity of the recombinant N-terminal Phl p5a and the C-terminal Phl p5b as measured by skin prick test and histamine release assays was significantly higher than that of the respective parent molecules. Using pancreatic rather than nasal secretion, Phl p5b was completely degraded and its allergenicity was almost completely reduced. Proteolytic degradation converts Phl p5 to defined fragments with increased allergenicity. Complete degradation of Phl p5 on the mucosa could be a preventive strategy to destroy its potency for the induction of an allergic response.

Analysis of cytokine profile in human colonic mucosal Fc epsilonRI-positive cells by single cell PCR: inhibition of IL-3 expression in steroid-treated IBD patients

Mast cells can serve as a possible important source of cytokine production in inflamed tissue which can be regulated by stimuli different from those activating other immune system cells. To study the expression of specific genes in mast cells derived from small human colonic mucosal endoscopic biopsies, we first modified a previously reported procedure to achieve a significantly enriched mast cell fraction. Then, by using single-cell RT-PCR analysis the expression of the IgE Fc receptor (Fc epsilonRI) and c-kit mRNA was determined. It was observed that the Fc epsilonRI-positive cells also expressed c-kit. This observation provided further evidence that Fc epsilonRI-positive cells are indeed mast cells. Analysis of biopsies from 12 patients (four control and eight patients with inflammatory bowel disease (IBD)) was carried out, revealing that all of the Fc epsilonRI-positive cells expressed IL-3, while the expression of IL-4 was detected only in some of these positive cells. TNF alpha was not detected in these cells. Therefore, it would seem that most intestinal mast cells produce IL-3. Since it has been reported that IL-3 synthesis was down-regulated in steroid-treated cells, the expression pattern of IL-3 in intestinal mast cells derived from steroid-treated IBD patients was then determined. IL-3 mRNA was detected in only two out of 24 Fc epsilonRI-positive cells derived from these steroid-treated patients. These results lend strong support to the idea that the down-regulation of IL-3 in mast cells derived from steroid-treated IBD patients occurs in vivo and could be an important mechanism for immunomodulation in IBD.

Mast cell ultrastructure in the inferior turbinate and stroma of nasal polyps

Fourteen unselected adult patients with nasal polyps had ultrastructural examination of mast cells from matching biopsies of the polyp and inferior turbinate. Between three and 10 blocks were examined for each patient in both tissues and every mast cell that had a nucleus was photographed for study. Fifty-three mast cells were found within the stroma of nasal polyps and 54 in the submucosa of the inferior turbinate biopsies. The number of granules ranged between 13 and 167 (mean 60) for polyps and 18 and 148 (mean 61) in the inferior turbinate. The mast cells appeared essentially normal in the inferior turbinate of four patients. The degree of degranulation of the mast cells was calculated as in previous studies and then averaged for both the polyp and the inferior turbinate of each patient. There was greater degranulation in the nasal polyp compared to inferior turbinate (p = 0.03). These results were compared with mast cell degranulation found in the normal nose and in the inferior turbinate of patients with perennial allergic rhinitis which we previously published. The inferior turbinates in these patients were more degranulated than the normal nose (p = 0.0001) but were similar to that found in patients with perennial allergic rhinitis. This suggested that some degree of degranulation may occur throughout the nose in two thirds of the patients with nasal polyps which supports the theory that mast cell reactions are not limited to the polyps in a proportion of patients.

Mast cells that reside at different locations in the jejunum of mice infected with Trichinella spiralis exhibit sequential changes in their granule ultrastructure and chymase phenotype

Whether or not a nontransformed, mature mouse mast cell (MC) or its committed progenitor can change its granule protease phenotype during inflammatory responses, has not been determined. To address this issue, the granule morphology and protease content of the MC in the jejunum of BALB/c mice exposed to Trichinella spiralis were assessed during the course of the infection. Within 1 wk after helminth infection of the mice, increased numbers of MC appeared in the crypts at the base of the villi, and by wk 2 the number of MC throughout the villi increased by approximately 25-fold. Shortly after the peak of the mastocytosis, the intraepithelial population of MC disappeared, followed by a progressive loss of lamina propria MC. The presence of stellate-shaped granules containing crystalline structures in intraepithelial MC at the height of infection and the retention of such granules with fragmented crystals in lamina propria MC during resolution of the mastocytosis suggest that MC migrate during the various phases of the inflammation. As assessed by immunohistochemical analyses of serial sections, predominant chymase phenotypes were observed at the height of the infection in the muscle that expressed mouse MC protease (mMCP) 5 without mMCP-1 or mMCP-2 and in the epithelium that expressed mMCP-1 and mMCP-2 without mMCP-5. Accompanying these two MC populations were transitional forms in the submucosa that expressed mMCP-2 and mMCP-5 without mMCP-1 and in the lamina propria that expressed mMCP-2 alone. These data suggest that jejunal MC sequentially express mMCP-2, cease expressing mMCP-5, and finally express mMCP-1 as the cells progressively appear in the submucosa, lamina propria, and epithelium, respectively. In the recovery phase of the disease, MC sequentially cease expressing mMCP-1, express mMCP-5, and finally cease expressing mMCP-2 as they present at the tips of the villi, the base of the villi, and the submucosa, respectively. That MC can reversibly alter their protease phenotypes suggests that a static nomenclature with fixed functional implications is inadequate to describe MC populations during an inflammatory process within a particular tissue.

Immunoelectron microscopic localization of galectin-3, an IgE binding protein, in human mast cells and basophils

Galectin-3 is an endogenous soluble lectin within the family called galectins that bind beta-galactosides. Homologs of the protein isolated from different sources were previously designated as IgE-binding protein (epsilon BP), CBP35, CPB30, Mac-2, RL-29, RLL, L-29, and HL-29. All are now renamed galectin-3. This lectin is widely distributed in cells and tissues of mice, rats, dogs, hamsters, and humans. Light microscopic immunohistochemistry and ultrastructural immunogold labeling methods were used to determine the distribution of galectin-3 in human mast cells of several organs, in mast cells developed in vitro from human fetal liver cells, and in human peripheral blood basophils. Immunolabeling for the protein was observed in mast cells from all sources and in basophils. The lectin was detected in the nucleus and/or the cytoplasm. The nuclear labeling was over heterochromatin whereas euchromatin was unlabeled. Cytoplasmic labeling was concentrated over secretory granules. The intensity of staining generally was greater in mast cells of skin when compared with that of mast cells in other locations and with that of basophils. Studies have indicated that in mast cells galectin-3 may be involved in promoting their adhesion to basal laminae. In this study the localization of galectin-3 in the secretory granules of human mast cells and basophils suggests that these cells may release this lectin when activated to degranulate.

Granule swelling in stimulated bovine adrenal chromaffin cells: regulation by internal granule pH

Adrenal medullary chromaffin cells secrete catecholamines through exocytosis of their intracellular chromaffin granules. Osmotic granule swelling has been implicated to play a role in the generation of membrane stress associated with the fusion of the granule membrane. However, controversy exists as to whether swelling occurs before or after the actual fusion event. Using morphometric methods we have determined the granule diameter distributions in rapidly frozen, freeze-substituted chromaffin cells. Our measurements show that intracellular chromaffin granules increase in size from an average of 234 nm to 274 nm or 277 nm in cells stimulated to secrete with nicotine or high external K+, respectively. Granule swelling occurs before the formation of membrane contact. Ammonium chloride, an agent which inhibits stimulated catecholamine secretion by approximately 50% by altering the intragranular pH, also inhibits granule swelling. In addition, ammonium chloride-treated secreting cells show more granule-plasma membrane contacts than untreated secreting cells. Sodium propionate induces granule swelling in the absence of secretagogue and has been shown to enhance nicotine- and high K(+)- induced catecholamine release. These results indicate that in adrenal chromaffin cells granule swelling is an essential step in exocytosis before fusion pore formation, and is related to the pH of the granule environment.

Mast cell ultrastructure in the adenoids of children with and without secretory otitis media

This study was designed to compare the differences in morphology of the mast cells from the adenoid in children with otitis media with effusion (OME) and those from children with recurrent tonsillitis. Tissue for electron microscopy was prepared in the standard manner and between three and 10 blocks were examined for each child. All the mast cells with nuclei were photographed and the condition of the granules noted. The number of electron dense granules in each cell was assessed on a scale between zero and 10. Sixteen unselected children with OME were compared with 19 children with recurrent tonsillitis. There were no obvious differences in the degree of degranulation between the two groups although there was more vacuolation than previously described in the normal nose but less than in those patients with perennial allergic rhinitis. Allergy and mast cell reactions do not seem to predispose to OME. It was concluded that the adenoids are not the ideal tissue in which to study normal mast cells.

Histochemistry and morphology of porcine mast cells

Mast cells have been described extensively in rodents and humans but not in pigs, and the objective of this study was to characterize porcine mast cells by histochemistry and electron microscopy. Carnoy's fluid proved to be a good fixative but fixation with neutral buffered formalin blocked staining of most mast cells. Alcian Blue stained more mast cells than did Toluidine Blue (pH 0.5), although Alcian Blue also stained goblet cells. In pigs, unlike rodents, the Alcian Blue method did not distinguish between mast cells in the intestinal mucosa and those in the connective tissue of the intestinal submucosa, tongue and skin. Mast cells were significantly larger in adult pigs than in piglets; in adult pigs and piglets, mast cells in the intestinal mucosa were significantly larger than those in submucosal connective tissue, and they were more varied in shape in piglets and adults. Granules in mast cells in the intestinal mucosa stained less intensely than those in mast cells in connective tissue of tongue, skin and intestinal submucosa. Mast cells in the connective tissue of the tongue, skin and intestinal submucosa fluoresced strongly when stained with berberine sulphate or with a mixture of berberine sulphate and Acridine Orange, but mast cells in the intestinal mucosa did not. All mast cells reacted positively in an enzyme-histochemical method previously used to detect human tryptase but not in a method previously used to detect human chymase. Mast cells in the medulla of thymus stained similarly to mast cells in the intestinal mucosa. Ultrastructural differences between mast cells were not detected.

Heterogeneity of mast cells at multiple body sites. Fluorescent determination of avidin binding and immunofluorescent determination of chymase, tryptase, and carboxypeptidase content

Human mast cells (MCs) from multiple sites were studied to determine heterogeneity of expression of chymase, tryptase, and/or carboxypeptidase and the binding to avidin. Three immunophenotypes were found: MCs positive for tryptase (MCT), no immunodetectable chymase; MCs positive for tryptase and chymase (MCTC); and MCs positive for chymase (MCC), no immunodetectable tryptase. Chymase-positive MCs also bound avidin and contained carboxypeptidase. In breast skin and parenchyma and axillary lymph nodes > 95% were MCTC; a rare MC in skin and lymph nodes was MCT or MCC. In lung alveoli 91% of MCs were MCT, 8% were MCTC and 1% MCC. In bowel mucosa 58% of MCs were MCT, 35% were MCTC and 7% MCC, whereas in bowel submucosa 83% of MCs were MCTC and 17% MCC. Within esophageal epithelium 38% were MCT and 62% MCTC; whereas, in esophageal subepithelium all were MCTC. This study further documents site-dependent diversity among normal human MCs and recognizes a novel third immunophenotype rich in chymase and relatively deficient in tryptase, the MCC cell.

Lung mast cells increase in number and degranulate during pulmonary artery occlusion/reperfusion injury in dogs

The role of mast cells in pulmonary artery occlusion/reperfusion injury was examined. Lung tissue was obtained from dogs after left pulmonary artery occlusion for 48 h (n = 5) or after similar occlusion followed by 4 h of reperfusion (n = 11). By light microscopy and morphometry, the percentage of mast cells increased 2.4-fold (p < 0.05) in nonoccluded right lungs and 2.9-fold (p < 0.05) in occluded left lungs without reperfusion compared with that in control lungs. After reperfusion, the occluded left lung contained 1.8-fold (p < 0.05) as many mast cells as the nonoccluded right lung and 4.2-fold (p < 0.05) more than that in control lungs. Hydroxyurea did not significantly affect the number of mast cells observed in the right and left lungs after ischemia/reperfusion; 39.8% and 54.4% of the mast cells were degranulated in nonoccluded right lung and occluded left lung preparations, respectively, after left pulmonary artery ischemia/reperfusion (each, p < 0.05 compared with control lungs). The release of eicosanoids into the airways during ischemia/reperfusion injury was also examined. Thromboxane B2 and leukotriene B4 were markedly increased (each, p < 0.05 compared with that in control lungs) in bronchial lavage fluids from both nonoccluded and occluded lungs compared with sham-occluded lungs. Thus, mast cell recruitment and degranulation may play a role in lung ischemia/reperfusion injury.

Degranulation of cystic fibrosis nasal polyp mast cells

The ultrastructure of nasal polyps from cystic fibrosis (CF) patients was compared with non-CF nasal polyps in this study. Morphometric analysis showed that CF nasal polyps contained greater numbers of mast cells, endothelial cells, lymphocytes, and plasma cells compared with the non-CF specimens. Morphologic evidence of degranulation was seen in approximately 30 per cent of the CF mast cells but was not observed in the non-CF mast cells. Increased numbers of small granules, vacuolated granules, and lipid bodies were noted in the CF compared with the non-CF nasal polyp mast cells. Also observed was a decrease in collagen in the extracellular space of the CF nasal polyps compared with the non-CF specimens. Although eosinophils were observed in the non-CF nasal polyp tissue, these leukocytes were absent in the CF nasal polyps. These data indicate that striking morphologic differences exist between CF and non-CF nasal polyps with mast cell degranulation, a salient feature of CF specimens.

Cloning and characterization of the novel gene for mast cell carboxypeptidase A

No gene for a hematopoietic cell carboxypeptidase has previously been characterized. Mast cell carboxypeptidase A (MC-CPA) is a prominent secretory granule marker of mast cell differentiation and phenotype. The 32-kb human MC-CPA gene was isolated, localized to chromosome 3, and found to contain 11 exons. No significant homology was found between the 5' flanking region of the MC-CPA gene and those of three rat pancreatic carboxypeptidase genes (carboxypeptidase A1 and A2, and carboxypeptidase B [CPB]). In contrast, the intron/exon organization of the MC-CPA gene was conserved, most closely resembling the CPB gene. MC-CPA is unique among carboxypeptidases in having a CPA-like substrate-binding pocket and enzymatic activity despite overall protein and gene structures more similar to CPB. Evolutionary tree analysis of the carboxypeptidase gene family showed that, before the mammalian species radiation, a common MC-CPA/CPB ancestor diverged by gene duplication from the lineage leading to CPA, and then underwent another gene duplication to form separate but similar gene structures for MC-CPA and CPB. MC-CPA mRNA was prominent in dispersed lung cells enriched for mast cells but was undetectable in other nontransformed populations of several lineages, demonstrating that transcription of MC-CPA, a novel carboxypeptidase gene, provides a specific molecular marker for mast cells among normal hematopoietic cell populations.

Ultrastructure of nasal mast cells in normal subjects and patients with perennial allergic rhinitis

The ultrastructure of mast cells from the nine normal inferior turbinates were compared with those found in eight patients with perennial allergic rhinitis due to house dust mite allergy. Forty-six mast cells from normal patients were found in forty blocks and eighty cells were found in thirty-three blocks in patients with perennial allergy suggesting an increase of mast cell numbers in perennial allergy. There were no basophils outside the blood vessels and whole mast cells were found only in the submucosa. There was no difference in the morphology of cells of different sizes. Mast cells were more degranulated in the allergic mucosa. Degranulation, irrespective of cell size was found at all depths of the mucosa. A review of the literature covered the in vivo and in vitro descriptions of the ultrastructural morphology of human mast cells in the respiratory tract.

Extracellular localization of human connective tissue mast cell granule contents

In early phases of cutaneous inflammation, connective tissue mast cell degranulation is associated with apparent secretion and externalization of immunoreactive chymotryptic serine proteinase. To determine whether this event is associated with structural evidence of granule externalization, we studied the sequential evolution of IgE-mediated hypersensitivity in vivo, as well as mast cell degranulation provoked by a variety of stimuli in cultured explants of human skin. By 1 min after intradermal antigen challenge with ragweed extract, mast cell degranulation was associated with apparent extrusion of intragranule constituents into the pericellular connective tissue. Similar features typified cultured skin explants exposed for 45 min to anti-IgE and other mast cell secretagogues (morphine sulfate, calcium ionophore A23187, compound 48/80, and substance P). Once externalized, granule constituents could be identified within the dermal matrix by their rounded contour and structural similarity to solubilized granule matrices remaining within actively secreting cells. These data indicate that externalization of connective tissue mast cell granule contents occurs early after secretagogue exposure, potentially accounting for infrequent documentation of this event in naturally occurring dermatoses. The ability to recognize externalized granule products at a morphologic level should facilitate the understanding of interactions between mast cell-derived mediators and target structures of the dermal microvasculature.

Biological properties of human skin mast cells

Mast cells and basophils, although sharing many constitutive properties, are quite distinct in their development, functions and biological properties. Mast cell granules are composed of a macromolecular matrix of proteoglycan and neutral protease of which heparin and tryptase, respectively, are predominant. The distribution of the other major neutral protease, chymase, allows human mast cell subpopulations to be subdivided immunocytochemically. All human mast cells respond to IgE-dependent stimulation with the secretion of the preformed mediator, histamine, and the newly generated lipid-derived eicosanoids PGD2 and LTC4. Although amounts of these products vary between mast cells dispersed from different tissues, it is uncertain whether this reflects true heterogeneity. Mast cells of the human skin, but not those of other tissues, are sensitive to stimulation by substance P, compound 48/80 and other basic non-immunological stimuli. The mechanism of mediator secretion induced by these agents is distinct from that induced by IgE-dependent stimulation. However, the morphological characteristics of degranulation are similar, suggesting that the distinct biochemical pathways merge into a common pathway before effecting degranulation.

The ultrastructure of mast cells in the uterus throughout the normal menstrual cycle and the postmenopause

During the menstrual cycle a gradation in mast cell granule ultrastructure was observed from the functional endometrium towards the myometrium of the uterus. Mast cells with particulate granules were present in the functional endometrium and those with granules containing identifiable scrolls in the basal layer of the endometrium and in the myometrium; mast cells containing very electron-dense granules were present in the deeper layers of the myometrium. The secretory activity of mast cells throughout the menstrual cycle is described. Mast cell secretion was observed to a lesser extent in the postmenopausal uterus. Mast cells with particulate granules were absent in the postmenopausal uterus and many very electron-dense granules were observed in mast cells in the myometrium.

Ultrastructural and Immunohistochemical Characterization of Normal Mast Cells at Multiple Body Sites

This article reviews the ultrastructural and immunohistochemical features of normal human mast cells (MC) at multiple tissue sites. Current literature indicates that granules containing discrete scrolls (scroll-rich morphology) are frequent in MC from bowel mucosa and lung, locations where the majority of MC show only tryptase immunoreactivity (MC(T)). In contrast, most MC from skin, breast parenchyma, axillary lymph nodes, and bowel submucosa are characterized by scroll-poor morphology (that is, granules are rimmed by incomplete scrolls forming parallel lamellae and containing central, amorphous granular material or grating/lattice-like structures) and show both tryptase and chymase immunoreactivity (MC(TC)). MC having granules with both scroll-rich and scroll-poor features can occur in all tissue sites, and an occasional MC, especially in lung and bowel, may show only chymase immunoreactivity (MC(C)). Chymase immunoreactivity in MC also is closely associated with avidin binding and carboxypeptidase reactivity. We conclude that there is ultrastructural and immunophenotypic diversity among normal human MC, although certain forms predominate in specific tissue environments. In skin, breast tissue, axillary lymph nodes, and bowel submucosa MC tend to have scroll-poor granules and stain for avidin, chymase, tryptase, and carboxypeptidase, whereas, in lung and bowel mucosa MC granules tend to be scroll-rich and stain only for tryptase with currently available reagents.

Proteoglycans in haemopoietic cells

Proteoglycans are produced by all types of haemopoietic cells including mature cells and the undifferentiated stem cells. The proteinase-resistant secretory granule proteoglycan (serglycin; Ref. 14), is the most prevalent and best characterised of these proteoglycans. Although its complete pattern of distribution in the haemopoietic system is unknown, serglycin has been identified in the mast cells, basophils and NK cells, in which secretion is regulated, and in HL-60 cells and a monocytoid cell line (Kolset, S.O., unpublished data) in which secretion is constitutive. Proteinase-resistant proteoglycans have been detected in human T-lymphocytes and murine stem cells (FDCP-mix) and the core proteins may be closely related to serglycin. A variety of glycosaminoglycan chains are assembled on the serglycin protein and it is likely that this class of proteoglycan can carry out a wide variety of functions in haemopoietic cells including the regulation of immune responses, inflammatory reactions and blood coagulation. There is strong evidence that in mast cells, NK cells and platelets, the proteoglycans are complexed to basic proteins (including enzymes and cytolytic agents) and amines in secretory granules and such complexes may dissociate following secretion from the cell. The stability of the complexes may be regulated by the ambient pH which may be acidic in the granules and neutral or above in the external medium. However, proteinase-proteoglycan complexes in mast cell granules seem to remain stable after secretion and it has been proposed that the proteoglycan regulates activity of proteinases released into the pericellular domain. The functions of proteoglycans which are constitutively secreted from cells are less clear. If cells have no requirement for storage of basic proteins why do they utilise the same design of proteoglycan as cells which accumulate secretory material prior to regulated release? We should stress that the so-called constitutive secretory pathway has been identified in haemopoietic cells in culture, which are usually maintained and grown in the presence of mitogenic factors (e.g., IL-2, IL-3). the cells are therefore activated and it has not been established that continuous proteoglycan secretion occurs in quiescent cells circulating in the peripheral blood. It is possible that lymphocytes, monocytes and macrophages, in which the constitutive secretion pathway operates in vitro, may store proteoglycan in vivo unless stimulated by mitogens or other activating agents.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of prolonged incubation of rat peritoneal mast cells with compound 48/80

Rat peritoneal mast cells (MC) co-cultured on a monolayer of 3T3 fibroblasts (MC/3T3) were continuously exposed to compound 48/80 for 14 days. As early as 2 days following continuous exposure to compound 48/80, the MC/3T3 appeared as a heterogeneous population, with various MC appearing partially or fully degranulated or intact; this morphological pattern continued throughout the duration of the experiment. MC/3T3 remained functionally active as demonstrated by their ability to secrete histamine 15 min after each replacement with fresh medium containing compound 48/80, although this capacity diminished towards the end of the 14-day experiment. Concomitant with the histamine release, a significant increase in cellular histamine pools was observed. When MC/3T3 continuously exposed to compound 48/80 for 7 or 14 days were acutely challenged with anti-IgE antibodies, they were able to secrete histamine and prostaglandin D2 in amounts similar to those produced by control MC. In contrast, when these cells were challenged on day 7 or 14 with a higher dose of compound 48/80 or with substance P, the release of histamine was partially inhibited. Our results indicate that continuous in vitro exposure to compound 48/80, and the resulting MC degranulation product histamine, does not adversely affect the ability of MC/3T3 to synthesize histamine and to respond to activation stimuli of a related secretagogue for 7 days and a non-related one for at least 14 days.

Mast cells in the bovine lower respiratory tract: morphology, density and distribution

The lower respiratory tract of six 8-day-old calves and six adult cows was fixed in either isotonic formal-acetic-acid or neutral buffered formalin in order to study the morphology, density and distribution of mast cells. They were found at all levels of the tract with the highest density in the major bronchi. Tissues from cows had significantly more mast cells than those from calves. There were significantly more mast cells detected in calf airways fixed with isotonic formal-acetic-acid compared with those seen in the same tissues fixed with neutral buffered formalin. Regardless of the age and fixation, mast cells were located predominantly in the alveolar septa and in the lamina propria of airways. They were also commonly encountered within the mucosal epithelium of the trachea. Ultrastructurally, mast cells in bovine airways and lung contained two types of intracytoplasmic granules as described in other species.

Morphological, histochemical and ultrastructural features of the globule leukocyte of the bovine respiratory tract

The histochemical and ultrastructural features of the globular leukocyte of the bovine respiratory tract is described and found to be similar to those localized in the abomasum and bile ducts of cattle. Histochemical analysis of these cells demonstrated low amounts of carboxylated mucin mixed with neutral mucin and large amounts of basic protein. Two types of globules were seen in the leucocytes; one with a homegeneous electron dense material and another with vesiculated, crastalloid containing bodies.

Mast cells and multiple sclerosis: a light and electron microscopic study of mast cells in multiple sclerosis emphasizing staining procedures

In the brains of 7 patients with multiple sclerosis, mast cells were observed within the demyelinated plaques, in the border zone of the plaques as well as in seemingly normal white matter. The cells were mostly located in close connection with small vessels. The routine staining with toluidine blue for the demonstration of mast cells is not adequate as compared with staining of similar sections in pinacyanol erythrosine. Mast cells may be a hitherto underestimated contributor to the demyelinating process of multiple sclerosis.

Degranulation of human mast cells induces an endothelial antigen central to leukocyte adhesion

To understand better the role of mast cell secretory products in the genesis of inflammation, a system was developed for in vitro degranulation of human mast cells in skin organ cultures. Within 2 hr after morphine sulfate-induced degranulation, endothelial cells lining microvessels adjacent to affected mast cells expressed an activation antigen important for endothelial-leukocyte adhesion. Identical results were obtained when other mast cell secretagogues (anti-IgE, compound 48/80, and calcium ionophore A23187) were used. Induction of this antigen was abrogated by preincubation with cromolyn sodium, an inhibitor of mast cell secretion, and by antiserum to tumor necrosis factor alpha. These findings indicate that degranulation of mast cells activates dermal endothelium through tumor necrosis factor-dependent mechanisms. This event may be critical to the elicitation phase of cutaneous inflammation.