Mast Cell Granules Research Articles

Serum mast cell tryptase is not a useful marker for disease severity in psoriasis or atopic dermatitis

Severity in psoriasis and atopic dermatitis (AD) is commonly assessed with the Psoriasis Area and Severity Index (PASI) and the SCORing Atopic Dermatitis (SCORAD), respectively. Until today no serum marker is available to reflect the clinical scoring in both diseases. As mast cells play an important role in the pathogenesis of early psoriasis and AD, tryptase, a major compound of mast cell granules that is released upon activation, could in principle serve as such a marker. To assess the correlation between serum tryptase and severity of psoriasis and AD as well as the correlation between total IgE levels and severity of AD. Serum samples from patients hospitalized for psoriasis and AD were collected at time of admission and time of discharge from hospital. PASI and SCORAD assessments were performed at the same time points. Outpatients presenting with naevi and other benign noninflammatory skin lesions served as control group. Serum tryptase values and total IgE levels of patients with AD were measured using a fluoroenzyme immunoassay technique. No correlation of serum tryptase level with either the severity of psoriasis or the severity of AD was seen. Total IgE levels in patients with AD at time of admission and discharge from hospital remained the same. Serum total tryptase did not prove to be a useful tool in assessing severity of psoriasis or AD. Total IgE levels did not correlate with severity of AD.

Reduction with dithiothreitol causes serglycin-specific defects in secretory granule integrity of bone marrow derived mast cells

Mast cell granule maturation and storage of granule components has previously been shown to be critically dependent on serglycin (SG), a proteoglycan abundantly stored in mast cell secretory granules. The N-terminal portion of serglycin contains a conserved disulfide motif that is similar to motifs found in secretory granule compounds of neuroendocrine cells. Interference with such motifs of neuroendocrine cells with dithiothreitol (DTT) has previously been shown to cause cellular missorting. To investigate the implication for serglycin, serglycin +/+ and serglycin −/− bone marrow derived mast cells (BMMCs) were treated with DTT followed by assessment of proteoglycan synthesis and secretory granule integrity. Treatment of serglycin +/+ BMMCs with DTT almost completely abolished biosynthetic incorporation of 35S-sulfate into proteoglycans, caused a dramatic reduction of granular staining with May Grünwald/Giemsa as well as disruption of granule dense core formation as shown by transmission electron microscopy. In addition, the storage of carboxypeptidase A, a major secretory granule compound, was markedly reduced following DTT treatment. In contrast, none of these effects were seen after treatment of SG −/− BMMCs with DTT, indicating that they were serglycin-specific. Notably, DTT treated serglycin +/+ BMMCs showed similar morphology as did the serglycin −/− BMMCs. DTT treatment affected neither the viability of the BMMCs nor the mRNA levels for serglycin or carboxypeptidase A. Together, these data indicate that DTT causes dramatic, serglycin-specific effects on mast cell granule. These findings are thus in accordance with a role for the N-terminal disulfide motif in serglycin for regulation of mast cell secretory granule integrity.

A Catalytic Role of Heparin within the Extracellular Matrix

We investigated the mechanism by which heparin enhances the binding of vascular endothelial growth factor (VEGF) to the extracellular matrix protein fibronectin. In contrast to other systems, where heparin acts as a protein scaffold, we found that heparin functions catalytically to modulate VEGF binding site availability on fibronectin. By measuring the binding of VEGF and heparin to surface-immobilized fibronectin, we show that substoichiometric amounts of heparin exposed cryptic VEGF binding sites within fibronectin that remain available after heparin removal. Measurement of association and dissociation kinetics for heparin binding to fibronectin indicated that the interaction is rapid and transient. We localized the heparin-responsive element to the C-terminal 40-kDa Hep2 domain of fibronectin. A mathematical model of this catalytic process was constructed that supports a mechanism whereby the heparin-induced conformational change in fibronectin is accompanied by release of heparin. Experiments with endothelial extracellular matrix suggest that this process may also occur within biological matrices. These results indicate a novel mechanism whereby heparin catalyzes the conversion of fibronectin to an open conformation by transiently interacting with fibronectin and progressively hopping from molecule to molecule. Catalytic activation of the extracellular matrix might be an important mechanism for heparin to regulate function during normal and disease states.

Oral chymase inhibitor SUN13834 ameliorates skin inflammation as well as pruritus in mouse model for atopic dermatitis

Chymase is a chymotrypsin-like serine protease exclusively stored in secretory granules of mast cells and has been thought to participate in allergic diseases. It has already been shown that chymase inhibitor SUN13834 improves dermatitis in NC/Nga mice that spontaneously develop dermatitis resembling atopic dermatitis. In the present study, effect of chymase inhibitor SUN13834 on itch, the major feature of atopic dermatitis, was examined using a mouse dermatitis model induced by repeated topical application of 2,4-dinitrofluorobenzene (DNFB). Oral administration of SUN13834 once a day for 5 weeks inhibited not only skin swelling but accumulation of inflammatory cells including mast cells and eosinophils in the skin of the mice. In addition, SUN13834 also decreased significantly at 10 and 50 mg/kg the amount of scratching behavior induced by the DNFB challenge. This result indicates for the first time that mast cell chymase may be involved in itch induction. In conclusion, SUN13834 is thought to be useful as therapeutic agent for atopic dermatitis.

Chondroitin 4-O-Sulfotransferase-1 Modulates Wnt-3a Signaling through Control of E Disaccharide Expression of Chondroitin Sulfate

Wnt-3a is a ligand that activates the beta-catenin-dependent pathway in Wnt signaling, which is implicated in numerous physiological events such as morphogenesis. So far, heparan sulfate (HS) proteoglycans have been highlighted as a low affinity receptor for morphogens containing Wnts. Here we show the importance of chondroitin sulfate (CS) proteoglycans in the efficient signaling of Wnt-3a and the structural features of CS required for the regulation of Wnt-3a signaling. Wnt-3a signaling was depressed in a mouse L cell mutant, called sog9, which is defective in the EXT1 gene encoding the HS-synthesizing enzyme and the chondroitin 4-O-sulfotransferase (C4ST-1) gene compared with parental L cells. The transfection of sog9 cells with C4ST-1 resulted in the recovery of Wnt-3a signaling, whereas the expression of EXT1 in sog9 cells could not restore Wnt-3a signaling. In addition, the expression level of introduced C4ST-1 correlated with the recovery of Wnt-3a signaling accompanied by the increased expression of the E disaccharide unit of CS. Interestingly, molecular interaction analyses using Biacore revealed that squid CS-E (rich in the E disaccharide unit) bound strongly to Wnt-3a (K(d)=13.2 nm) to the same extent as heparin from bovine lung (K(d)=8.43 nm). In contrast, other CS isoforms as well as HS isolated from bovine kidney showed little binding activity to Wnt-3a. Moreover, exogenously added CS-E potently inhibited the accumulation of beta-catenin induced by Wnt-3a. These results suggest that CS-E-like structures synthesized by C4ST-1 participate in Wnt-3a signaling and modulate the physiological events caused by Wnt-3a signals.

Secretogranin III Directs Secretory Vesicle Biogenesis in Mast Cells in a Manner Dependent upon Interaction with Chromogranin A

Mast cells are granular immunocytes that reside in the body's barrier tissues. These cells orchestrate inflammatory responses. Proinflammatory mediators are stored in granular structures within the mast cell cytosol. Control of mast cell granule exocytosis is a major therapeutic goal for allergic and inflammatory diseases. However, the proteins that control granule biogenesis and abundance in mast cells have not been elucidated. In neuroendocrine cells, whose dense core granules are strikingly similar to mast cell granules, granin proteins regulate granulogenesis. Our studies suggest that the Secretogranin III (SgIII) protein is involved in secretory granule biogenesis in mast cells. SgIII is abundant in mast cells, and is organized into vesicular structures. Our results show that over-expression of SgIII in mast cells is sufficient to cause an expansion of a granular compartment in these cells. These novel granules store inflammatory mediators that are released in response to physiological stimuli, indicating that they function as bona fide secretory vesicles. In mast cells, as in neuroendocrine cells, we show that SgIII is complexed with Chromogranin A (CgA). CgA is granulogenic when complexed with SgIII. Our data show that a novel non-granulogenic truncation mutant of SgIII (1-210) lacks the ability to interact with CgA. Thus, in mast cells, a CgA-SgIII complex may play a key role in secretory granule biogenesis. SgIII function in mast cells is unlikely to be limited to its partnership with CgA, as our interaction trap analysis suggests that SgIII has multiple binding partners, including the mast cell ion channel TRPA1.

Potential role of mast cells in hamster cheek pouch carcinogenesis

During the process of activation, mast cells release products stored in their granules. Tryptase, a protease released from mast cell granules after activation, induces tumor cell proliferation through the activation of PAR-2 (protease activated receptor 2) on the plasma membrane of carcinoma cells. Chemical cancerization (DMBA) of the hamster cheek pouch is the most accepted model of oral cancer. However, there are no reports on the activation of mast cells during experimental carcinogenesis or on the correlation between mast cell activation and cell proliferation. The aim of the present study was to evaluate the potential effect of mast cells on the proliferation of epithelial cells at different times during the cancerization process. Paraffin serial sections of cancerized, tumor-bearing pouches were stained with Alcian Blue-Safranin to identify the different degrees of mast cell activation. Immunohistochemistry was performed to identify BrdU-positive cells to study tumor cell proliferation. Mast cells were counted and grouped into two categories: inactive mast cells AB-S+++ (red) and active mast cells AB+++S- (blue). Mast cell counts were performed in tumor stroma, base of the tumor (connective tissue immediately below the exophytic tumor), connective and muscle tissue underlying the cancerized epithelium (pouch wall) and adventitious tissue underlying the pouch wall. There was a significant increase in the number of mast cells at the base of tumors (p<0.001) compared to the number of mast cells in the wall of the pouch and in tumor stroma. In normal non-cancerized pouches, inactive mast cells were prevalent both in the wall (AB:S=1:2.15; p<0.001) and in the adventitious tissue (AB:S=1:1.6; p<0.004) of the hamster cheek pouch. At most of the experimental times examined, the ratio of active/inactive mast cells (AB/S) in the wall approximated unity and even reverted. The ratio of mast cells was AB:S 1:1.05 at the base of the tumor and 1:0.24 in tumor stroma (p<0.001). The evaluation of epithelial nuclei labeled for BrdU revealed a statistically significant increase in cells undergoing DNA synthesis in the epithelium of the wall of the cancerized pouch compared to control (p<0.017). Tumor parenchyma exhibited a highly statistically significant increase in DNA synthesis compared to control (p<0.001) and compared to the epithelium of the wall of the cancerized pouch (p<0.036). We conclude that mast cell activation in this model is associated to the increase in tumor cell proliferation, conceivably mediated by the release of tryptase.

Chronic stress induced proliferation and activation of mast cells of gastric antrum in rats

To explore chronic heterotypic stressors induced proliferation and activation of mast cells in gastric antrum mucosa by ultrastructure alterations of mast cells, chronic unpredictable heterotypic stressors were used as a study model. The mean immunofluorescence magnitude of mast cell protease 1 (MCP-1) taken from chronic stress rats were 37.4±7.7, significantly higher (p<0.05) than the value of normal control group (24.8±5.6). Chronic unpredictable haterotypic stressors appeared also to induce ultrastructure alterations of mast cells. It indicated that mast cells were proliferated and activated, while mast cell granules were hyperplasiaed. Most granules had obvious intragranular changes with loss of electron-dense material. The morphologic evidence showed that macrophages and leukocytes infiltrated in chronic stress rats. Some granules of leukocytes adhered to the surface of mast cell, and formed a bridge. Macrophages phagocytized the mast cell granules.

Chimerism, point mutation, and truncation dramatically transformed mast cell δ-tryptases during primate evolution

Tryptases are serine peptidases stored in mast cell granules. Rodents express 2 soluble tryptases, mast cell proteases (MCPs) 6 and 7. Human alpha- and beta-tryptases are orthologs of MCP-6. However, much of the ancestral MCP-7 ortholog was replaced by parts of other tryptases, creating chimeric delta-tryptase. Human delta-tryptase's limited activity is hypothesized to be due to truncation and processing mutations. We sought to probe the origins and consequences of mutations in primate delta-tryptases. Prosimian (lemur), monkey (macaque), great ape (orangutan, gorilla, and chimpanzee), and human delta-tryptase genes were identified by means of data mining and genomic sequencing. Resulting genes were analyzed phylogenetically and structurally. The seminal conversion event generating the delta-tryptase chimera occurred early because all primates studied contain delta-tryptase genes. Truncation, resulting from a nonsense mutation of Trp206, occurred much later, after orangutans and other great apes last shared an ancestor. The Arg-3Gln propeptide mutation occurred most recently, being present in humans and chimpanzees but not in other primates. Surprisingly, the major active tryptase in monkeys is full-length delta-tryptase, not beta-tryptase, which is the main active tryptase in human subjects. Models of macaque delta-tryptase reveal that the segment truncated in human subjects contains antiparallel beta-strands coursing through the substrate-binding cleft, accounting for truncation's drastic effect on activity. Transformations in the ancestral MCP-7-like gene during primate evolution caused dramatic variations in function. Although delta-tryptases are nearly inactive in humans, they are active and dominant in monkeys.

The transcription of tryptase gene in human mast cells is regulated by mi transcription factor

Mast cells play a central role in initiation and development of allergic diseases through release of various mediators. Tryptase may be a key mediator in mast cell‐mediated inflammatory reactions. In the present study, we investigated whether the transcription of tryptase gene in human mast cells was involved in mi transcription factor (MITF). Human mast cells express strongly MITF‐A, which is one of MITF isoforms. We observed that overexpression of MITF‐A elevates the production of tryptase in the immature human mast cell line HMC‐1, while the introduction of specific siRNA against MITF attenuated their expression. The level of granules in mast cells also was increased by overexpression of MITF‐A. Moreover, the transfection of MITF‐A into Jurkat cells (MITF‐negative) increased significantly the luciferase activity. Using mutant constructs of tryptase promoter, we identified that two E‐box motifs associate with MITF‐A to transactivate tryptase gene. An experiment by EMSA also showed that these E‐box are major motifs binding to MITF for tryptase transcription. These data suggest that MITF might play a role in regulating the transcription of tryptase gene in human mast cells.Supported by the Korea Research Foundation Grant (KRF‐2006‐E00103).

Lewis Lung Carcinoma (LLC) alters the phenotype of murine lung mast cells resulting in a phenotype consistent with myeloid‐derived suppressor cells (MDSCs)

MDSCs are among the most potent immune suppressive phenotypes found in the tumor microenvironment. Because they share so many characteristics with myeloid progenitors, MDSCs are thought to arise as a product of tumor‐associated hematopoiesis. However, a clear MDSC progenitor has yet to be identified. We used flow cytometry to demonstrate a significant increase in CD11b+ infiltrate in a murine model of LLC as compared to normal lung tissue. A large portion of this infiltrate also expresses the granulocyte/myeloid marker Gr‐1. Interestingly, CD11b+/Gr‐1+ cells in normal lung tissue also express the high affinity IgE receptor FcεR1α, which is indicative of mast cells. However, this FcεR1α expression is lost on these cells in LLC‐bearing animals in a tumor burden‐dependant manner. Additionally, conventional methylene blue stains show highly granulated mast cells in normal lung tissue while showing a complete lack of granulated cells in LLC‐bearing lung tissue. We also immunomagnetically isolated Gr‐1+ mast cells out of normal lung tissue and incubated them in‐vitro with LLC‐conditioned media while monitoring their FcεR1α expression, granularity, and morphology in an attempt to reproduce the phenotypic changes seen in‐vivo. Our data suggests that in LLC, MDSCs may originate from fully differentiated mast cells rather than from myeloid precursors.Supported by the Dept of Veteran's Affairs &amp; NIH

Immunolocalization of atrial natriuretic peptide in mast cells of human and rat pericardium

It is known that various heart disorders are accompanied by an elevated level of atrial natriuretic peptide (ANP), a regulator of cardiovascular homeostasis, in the pericardial fluid. Which cells produce ANP in the pericardial cavity is unclear. Using immunoelectron microscopy, we examined ANP localization in human and rat pericardium. ANP-immunobinding material was found in granules of mast cells (MC) localized in pericardial connective tissue. In rat pericardium, the average MC size is 6.5 × 12.5 μm and the MC density is about 50 cells per 1 mm2 section area. For the human pericardium, these parameters are 9.1 × 13.6 μm and 10 cells per 1 mm2, respectively. The results show that MCs are probably implicated in the pericardial endocrine function and in controlling the ANP level in the pericardial cavity.

Effects of fluoxetine on mast cell morphology and protease-1 expression in gastric antrum in a rat model of depression

To investigate the effects of fluoxetine on depression-induced changes of mast cell morphology and protease-1 (rMCP-1) expression in rats. A Sprague-Dawley rat model of chronic stress-induced depression was established. Fifty experimental rats were randomly divided into the following groups: normal control group, fluoxetine+normal control group, depressed model group, saline+depressed model group, and fluoxetine+depressed model group. Laser scanning confocal microscopy (LSCM) immunofluorecence and RT-PCR techniques were used to investigate rMCP-1 expression in gastric antrum. Mast cell morphology was observed under transmission electron microscopy. ANOVA was used for statistical analysis among groups. Morphologic observation indicated that depression induced mast cell proliferation, activation, and granule hyperplasia. Compared with the normal control group, the average immunofluorescence intensity of gastric antrum rMCP-1 significantly increased in depressed model group (37.4+/-7.7 vs 24.5+/-5.6, P<0.01) or saline+depressed model group (39.9+/-5.0 vs 24.5+/-5.6, P<0.01), while there was no significant difference between fluoxetine + normal control group (23.1+/-3.4) or fluoxetine+depressed model group (26.1+/-3.6) and normal control group. The average level of rMCP-1mRNA of gastric antrum significantly increased in depressed model group (0.759+/-0.357 vs 0.476+/-0.029, P<0.01) or saline+depressed model group (0.781+/-0.451 vs 0.476+/-0.029, P<0.01), while no significant difference was found between fluoxetine+normal control group (0.460+/-0.027) or fluoxetine+depressed model group (0.488+/-0.030) and normal control group. Fluoxetine showed partial inhibitive effects on mast cell ultrastructural alterations and de-regulated rMCP-1 expression in gastric antrum of the depressed rat model. Chronic stress can induce mast cell proliferation, activation, and granule hyperplasia in gastric antrum. Fluoxetine counteracts such changes in the depressed rat model.

Pseudoxanthomatous mastocytosis

A 50‐year‐old woman presented with itchy, multiple, flat, yellowish, waxy papules and plaques diffusely involving her face, trunk, and upper extremities for 5 years (Fig. 1). Itching was moderate to severe in intensity and was episodic, without any identifiable aggravating or relieving factors. On rubbing the lesions with a blunt object erythema was elicited. Her ophthalmological examination was normal. Her complete hemogram was normal along with other routine investigations. Patient's slit skin smear for acid‐fast bacilli and rk39 dip‐stick ELISA for post‐kala‐azar dermal leishmaniasis were negative. Ultrasound examination of her abdomen was normal and skeletal survey showed no evidence of bony changes. Histological examination showed diffuse dense infiltrate of numerous mast cells filling up the papillary dermis and most of upper‐ and mid‐reticular dermis. Overlying epidermis showed moderate epidermal hyperplasia and hyperpigmentation. There was sparse scattering of neutrophils within the infiltrate. Extracellular mast cells granules were also seen (Fig. 2). Diagnosis of diffuse cutaneous mastocytosis of pseudoxanthomatous variety was made.Pretreatment photographs of the patient; (a) face; (b) trunkimageHistopathology showing dense diffuse infiltrate of numerous mast cells filling up the papillary dermis and most of the upper and mid‐reticular dermis (H&amp;E; a, ×100; b, ×400)imageThe patient was prescribed treatment in the form of H1 and H2 blockers (fexofenadine and ranitidine) and trimethylpsoralen and ultraviolet A (PUVA) photochemotherapy. After 2 months of treatment, there has been marked improvement in the appearance and itching.

Reduced immunostaining for c‐kit receptors in mucosal mast cells in inflammatory bowel disease

The deleterious effects of stress in inflammatory bowel disease (IBD) have been attributed to activation of the brain-gut axis (BGA) and its end effectors, mast cells (MC). We previously showed that cold pressor stress test (CPT) results in increased activation and degranulation (but not increased proliferation) of mucosal MC, mitochondrial damage to epithelial cells and mucosal protein oxidation in both healthy controls and IBD patients. These changes are more marked in IBD patients. This increased activation of MC in IBD could be due to (i) greater activation of the BGA or (ii) inherited or acquired abnormalities in mucosal MC. In the current study we investigated the latter possibility. To assess the effects of stress on mucosal MC in patients with IBD, seven controls and 15 subjects with inactive IBD underwent 5 consecutive days of CPT to activate the BGA. Endoscopic mucosal biopsies of the distal sigmoid colon were taken during unprepared sigmoidoscopy before the first CPT and after the last CPT, and formalin-fixed samples were stained for both MC granules (MCg) and for the c-kit receptor, which is present on MC membranes (MCm). Mast cell degranulation was assessed using electron microscopy. Mast cell granule staining suggested that IBD subjects do not have a significantly different number of MC compared with controls, either before or after stress. Mast cell membrane staining, in contrast, suggested that MC c-kit immunostaining was significantly reduced - at both baseline (P = 0.01) and post stress (P = 0.04) samples - in IBD patients compared to controls. MC c-kit immunostaining was independent of stress-induced MC degranulation. There was no significant change in MC number as a result of the stress intervention using either staining method in both groups. These data support our previous report that the size of the mucosal MC population in patients with inactive IBD is not altered by disease or by stress, yet MC in IBD are different (fewer c-kit receptors) and respond differently (greater activation) than MC in control subjects. It remains to be seen whether this abnormality is an inherited or acquired one and to identify its role and mechanism in tissue injury in the pathogenesis of IBD.

Differential expression of leukocyte immunoglobulin-like receptors on cord blood-derived human mast cell progenitors and mature mast cells

The leukocyte Ig-like receptors (LILRs) comprise a family of cell-surface immunoregulatory receptors with activating and inhibitory members. The inhibitory LILRs possess cytoplasmic ITIMs that down-regulate signaling by nonreceptor tyrosine kinase cascades. The activating members have a truncated cytoplasmic domain and signal through the FcR gamma chain. We examined the expression of LILRs on human mast cells during their development in vitro. Progenitor mast cells expressed cell surface inhibitory LILRB1, -B2, -B3, and -B4 and activating LILRA1. However, although mature cord blood-derived mast cells (hMCs) had detectable mRNA encoding multiple LILRs, none were expressed on the cell surface. Culture of progenitor mast cells or hMCs with various cytokine combinations failed to retain or induce cell surface expression of the LILRs. It is interesting that hMCs expressed LILRB5 in cytoplasmic granules and upon cross-linking of the high-affinity IgE receptor, released LILRB5 into the culture medium. Our results demonstrate that LILRs are developmentally regulated in human mast cells and that LILRB5 is expressed in mast cell granules and the release of soluble LILRB5 following IgE FcR-dependent stimulation, which has potential for amplification of mast cell-dependent, inflammatory responses.

Mast cells and degradation of pericellular and extracellular matrices: potential contributions to erosion, rupture and intraplaque haemorrhage of atherosclerotic plaques

Mast cells are present in advanced human atherosclerotic plaques, where they are thought to exert multiple effects on their neighbouring cells and on the extracellular matrix of the plaque. Extensive efforts at delineating their role(s) in atherosclerotic plaques have unravelled mechanisms by which plaque mast cells may render advanced atherosclerotic plaques susceptible to erosion, rupture or intraplaque haemorrhage and so modulate their stability. In these mechanisms, the key effector molecules are mast-cell-derived neutral proteases and pro-inflammatory cytokines. These effector molecules are synthesized and stored in the cytoplasmic secretory granules of mast cells and, once the mast cells are activated to degranulate, are released into the microenvironment surrounding the activated mast cells. In the plaques, the key target cells are endothelial cells and smooth muscle cells and their pericellular matrices. In addition, the various components of the extracellular matrix of the plaques, notably collagen, are degraded when the released mast cell proteases activate matrix metalloproteinases in the plaques. By rendering the plaque susceptible to erosion, to rupture or to intraplaque haemorrhage, the mast cells may contribute to the onset of acute atherothrombotic complications of coronary atherosclerosis, such as myocardial infarction.

Serglycin proteoglycan in hematologic malignancies: a marker of acute myeloid leukemia

Serglycin is the major cell-associated proteoglycan of hematopoietic cells. Previous work has demonstrated that serglycin may be involved in targeting some proteins to granules of cytotoxic lymphocytes, mast cells and neutrophils. We characterized the expression of serglycin in various hematologic malignancies by immunohistochemistry and ELISA. Serglycin expression was found to distinguish acute myeloid leukemia (AML) from acute lymphoblastic leukemia. In contrast to myeloperoxidase, serglycin was found to be a selective marker for immature myeloid cells, distinguishing AML from Philadelphia chromosome-negative chronic myeloproliferative disorders.

Secretory granule proteoglycans of mast cells and natural killer cells.

Proteoglycan research on cells that participate in immune responses has progressed from the early novel finding that heparin proteoglycans are present in the secretory granules of the connective tissue mast cell to the more recent findings that mucosal mast cells and natural killer (NK) cells possess chondroitin sulphate proteoglycans in their granules. Characterization studies of these intracellular proteoglycans have revealed that they all possess peptide cores which are very resistant to proteolytic degradation. Their glycosaminoglycans, however, differ in such parameters as the type of hexosamine, location of sulphation degree of sulphation, or extent of epimerization of the uronic acid. Amino acid compositional analyses of heparin proteoglycans from rat connective tissue mast cells and chondroitin sulphate E proteoglycans from mouse mucosal mast cells indicate that their peptide cores are homologous to, but possibly distinct from one another. It is not yet known if these differences reflect a species variation, are due to different post-translational proteolytic processing, or are the result of expression of distinct genes coding for different peptide cores. The proteoglycans of mast cells and natural killer cells are packaged in the granules with cationic proteins. In mast cells these proteins have been shown to be serine proteases, and when bound to the acidic proteoglycans their enzymic activity is inhibited. Since the type of glycosaminoglycan linked to the proteoglycan has been found to be a characteristic of that cell, the structure of the cell-associated proteoglycan has become one of the markers used to distinguish cells phenotypically. By following the expression of different proteoglycans during differentiation, the relationship of the two subclasses of mast cells has been determined.

Histamine ameliorates anti-glomerular basement membrane antibody-induced glomerulonephritis in rats

Anti-glomerular basement membrane (anti-GBM)-induced glomerulonephritis involves T-helper type 1 (Th1) responses leading to rapid crescent formation. As many inflammatory and immune responses in general are affected by histamine, we examined the effects of histaminergic ligands on immune renal injury in the rat. Female Wistar-Kyoto rats were injected intraperitoneally with an antibody against the GBMs. Histaminergic ligands were then injected twice daily for 5 days after which renal function was assessed by proteinuria. Treatment with histamine led to significant dose-dependent reductions in proteinuria compared to the control antibody-injected group and markedly decreased the number of crescentic glomeruli and macrophage infiltration of the glomeruli. Furthermore, histamine significantly decreased the plasma concentration of interleukin-12, a Th1-type cytokine compared to the antibody-injected control animals. Dimaprit, an H(2)/H(4) agonist, mimicked the effects of histamine on proteinuria and crescent formation. Clozapine, an H(4) agonist, tended to mimic the effects of histamine, whereas an H(1), mepyramine, or an H(2) antagonist, ranitidine, did not reverse the protective effect of histamine. We suggest that histamine may alleviate renal injury in anti-GBM glomerulonephritis by suppressing the immune response.