Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P15088 (mast cell)
 14,925 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Complement-dependent activation of immune cells is regulated by cell surface membrane receptors. In this study, expression of complement receptors (CR) on human blood basophils (n = 11), tissue mast cells (lung, n = 7; skin, n = 10; uterus, n = 4; tonsil, n = 3; heart, n = 10), and on respective human cell lines (basophil line KU-812, mast cell line HMC-1) was analyzed by the use of mAbs and indirect immunofluorescence. Normal blood basophils and KU-812 cells were found to express C5aR (CD88), membrane cofactor protein (CD46), decay-accelerating factor (CD55), and membrane attack complex inhibitory factor (CD59), as well as the previously recognized CR1 (CD35), CR3 alpha (CD11b), CR4 alpha (CD11c), and CR3/4 beta (CD18). Mast cells from all organs as well as HMC-1 cells expressed CD46, CD55, and CD59, but not CD11b, CD21, or CD35. The C5aR (CD88) was detectable on skin mast cells, a subset (5 to 15%) of cardiac mast cells, and on HMC-1 cells, but not on lung, uterus, or tonsillar mast cells (< 5%). Moreover, double immunoperoxidase staining (tryptase vs C5aR/CD88) revealed in situ expression of C5aR on skin, but not lung mast cells. Recombinant human (rh) C5a, at 10(-10) to 10(-7) M, induced secretion of histamine from basophils (rhC5a, 10(-8) M: 53.4 +/- 3.1% vs control < 5%) and from skin mast cells (rhC5a, 10(-8) M: 25.8 +/- 16.1% vs control < 10% histamine release), but not from other mast cells (rhC5a or control: < 10%, p > 0.05). The rhC5a-induced secretion of histamine from basophils and skin mast cells was inhibited by S5/1, a blocking Ab against CD88 (basophils: 37.2% to 75.1%; skin mast cells: 39.2% to 83.9% inhibition, p < 0.05). Together, this study shows that a) basophils and mast cells express a different profile of complement receptors, b) C5a-dependent mediator release in skin mast cells and basophils is mediated via CD88, and c) mast cells constitute a heterogeneous lineage in terms of expression of the C5a binding site CD88.
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PMID:Differential expression of complement receptors on human basophils and mast cells. Evidence for mast cell heterogeneity and CD88/C5aR expression on skin mast cells. 767 28

The phenotypic and biologic properties of malignant cells in a case of aggressive mastocytosis with multi-organ involvement, circulating mast cell precursors and absence of skin infiltrates were analyzed. Circulating mast cell precursors were detected by immunostaining using antibodies against mast cell tryptase as well as by electron microscopy. These progenitors were tryptase+/chymase- (MCT) and accounted for 10 to 20% of nucleated mononuclear blood cells (MNC). A subset of them contained metachromatic granules. As assessed by combined toluidine blue/immunofluorescence staining, the granulated mast cell precursors were found to express CD9 (P24), CD33 (gp67) and CD44 (Pgp-1), but not basophil-related markers (CD11b (C3biR), CDw17 (lactosylceramide), CD123 (il-3R alpha))or monocyte-related antigens (CD14, CD15). Expression of the mast cell growth factor (MGF) receptor, c-kit(CD117), was also demonstrable, whereas the skin mast cell marker C5aR (CD88) could not be detected on mast cell precursors. The ligand of c-kit, recombinant human (rh) stem cell factor (SCF = MGF), induced histamine release from circulating mast cell progenitors, whereas rhC5a, a potent skin mast cell-/basophil-agonist, was ineffective over the dose-range (10(-9) to 10(-7(M)) tested. Analysis of mast cell antigens in malignant mastocytosis or mast cell leukemias may be helpful to establish a diagnosis and to determine the phenotype of the clone.
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PMID:A case of malignant mastocytosis with circulating mast cell precursors: biologic and phenotypic characterization of the malignant clone. 855 22

The expression of the receptor for the anaphylatoxin C5a (C5aR, CD88) on the human mast cell line HMC-1 was studied with four anti-C5aR monoclonal antibodies directed to the N-terminal domain of the receptor. All antibodies bound to the human mast cell line HMC-1. The binding could be blocked by recombinant C5a and by peptide EX-1 representing amino residues 1-31 on the N-terminal domain of the C5aR. In addition, FITC-labelled C5a bound to HMC-1, and this binding could be blocked by unlabelled C5a or C5aR antibodies. C5aR-specific mRNA was detected in HMC-1 cells by RT-PCR which confirmed the expression of the C5aR gene made by these cells. Lymphocyte-conditioned medium, interferon-gamma or phorbol esters which have been shown to induce a down-regulation of C5aR on myeloid cells did not influence the expression of C5aR on HMC-1. C5a led to a transient mobilization of intracellular calcium in HMC-1 which could be inhibited by pre incubation of C5a with a C5a-specific antibody. In contrast to findings with granulocytes, HMC-1 did not respond to C5a(desArg), confirming previous findings with human skin mast cells. The findings show that (i) although HMC-1 differ from granulocytes in their responsiveness to C5a(desArg), they express similar C5aR and (ii) HMC-1 cells resemble skin mast cells in the expression and function of C5aR and may therefore serve as a model in future studies addressing the biology of this anaphylatoxin receptor on skin mast cells.
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PMID:The human mast cell line HMC-1 expresses C5a receptors and responds to C5a but not to C5a(desArg). 869 89

The expression of the receptor for the anaphylatoxin C5a on mast cells was studied with three monoclonal antibodies directed to the N-terminal domain of the C5a receptor. Human skin was investigated by immunohistology applied to sequential 2 micron sections of acrylate-embedded tissues. All anti-C5a receptor antibodies stained c-kit+ or tryptase+ cells which were metachromatic after toluidine blue staining in normal human skin. The binding of anti-C5a receptor antibodies was inhibitable by a peptide representing the first 31 amino acids of the C5a receptor. A similar expression of C5a receptors was found on mast cells in chronic psoriatic plaques. However, C5a receptors were not detectable on mast cells in weal and flare reactions or in lesional skin of uticaria pigmentosa. These findings suggest that (1) anti-C5a receptor antibodies directed to the N-terminal domain of the receptor are suitable tools for the identification of mast cells in acrylate-embedded sections of human skin, (2) mast cell activation in weal and flare reactions results in C5a receptor downregulation or receptor blockade and (3) mast cells in urticaria pigmentosa lack a typical marker of normal human skin mast cells.
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PMID:C5a receptors are detectable on mast cells in normal human skin and in psoriatic plaques but not in weal and flare reactions or in uticaria pigmentosa by immunohistochemistry. 904 41

Recent cloning of the human C3a receptor (C3aR) revealed that this receptor belongs to the large family of rhodopsin-type receptors. A unique feature of the C3aR is the large second extracellular loop comprising about 175 amino acid residues. We constructed combinatorial phage Ab libraries expressing single chain Fv Abs from BALB/c mice immunized with the affinity-purified second extracellular loop of the C3aR, fused to glutathione-S-transferase. A panel of anti-C3aR single chain Fv fragments (scFvs) was selected after four rounds of panning using the second extracellular loop of the C3aR, fused to the maltose binding protein as Ag. Sequencing of the clones obtained revealed three different groups of scFvs, the epitopes of which were mapped to two distinct regions within the loop, i.e., positions 185 to 193 and 218 to 226, representing the immunodominant domains of the loop. By flow cyotmetric analyses, the scFvs bound to RBL-2H3 cells transfected with the C3aR, but not to cells transfected with the C5aR or to nontransfected RBL-2H3 cells. In addition, the scFvs bound to the human mast cell line HMC-1. Immunofluorescence studies showed C3aR expression on polymorphonuclear granulocytes and monocytes, but not on lymphocytes. In addition, no C3aR expression was observed on human erythrocytes or platelets. Surprisingly, none of the scFvs alone or in combination inhibited C3a-induced Ca2+ mobilization from RBL-2H3 cells transfected with the C3aR. In addition, C3a did not displace binding of the scFvs to the receptor, strongly suggesting that the N-terminal part of the second extracellular loop is not involved in ligand binding.
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PMID:Site-directed C3a receptor antibodies from phage display libraries. 951 Jan 99

The C3a receptor (C3aR) is expressed on most human peripheral blood leukocytes with the exception of resting lymphocytes, implying a much higher pathophysiological relevance of the anaphylatoxin C3a as a proinflammatory mediator than previously thought. The response to this complement split product must be tightly regulated in situations with sustained complement activation to avoid deleterious effects caused by overactivated inflammatory cells. Receptor internalization, an important control mechanism described for G protein-coupled receptors, was investigated. Using rabbit polyclonal anti-serum directed against the C3aR second extracellular loop, a flow cytometry-based receptor internalization assay was developed. Within minutes of C3a addition to human granulocytes, C3aR almost completely disappeared from the cell surface. C3aR internalization could also be induced by PMA, an activator of protein kinase C. Similarly, monocytes, the human mast cell line HMC-1, and differentiated monocyte/macrophage-like U937-cells exhibited rapid agonist-dependent receptor internalization. Neither C5a nor FMLP stimulated any cross-internalization of the C3aR. On the contrary, costimulation of granulocytes with C5a, but not FMLP, drastically decreased C3aR internalization. This effect could be blocked by a C5aR-neutralizing mAb. HEK293-cells transfected with the C3aR, with or without Galpha16, a pertussis toxin-resistant G protein alpha subunit required for C3aR signal transduction in these cells, did not exhibit agonist-dependent C3aR internalization. Additionally, preincubation with pertussis toxin had no effect on C3a-induced internalization on PMNs. C3aR internalization is a rapid negative control mechanism and is influenced by the C5aR pathway.
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PMID:Modulation of C3a activity: internalization of the human C3a receptor and its inhibition by C5a. 1035 94

Mast cells are thought to play an important role in atherogenesis and plaque rupture, but their role in the subsequent platelet activation and thrombus formation is unclear. Tryptase positive cells (KU812T+) were established from the KU812 cell line as an in vitro model of human mast cells and used to study the effect of mast cell activation on human platelets. Overnight incubation of KU812T+ with IgE and subsequent challenge with anti-IgE caused the release of heparinoid substances which inhibited 1 microg/ml collagen-induced platelet aggregation. KU812T+ challenged with compound 48/80 produced a releasate that had no apparent heparinoid content but caused full platelet aggregation. These findings showed that, although activation of KU812T+ via FcepsilonR1 partially abrogated collagen-induced platelet aggregation, activation of the C5a receptor signalling pathway, by compound 48/80, caused the release of potent platelet-activating substances. This cell culture model offers a unique insight into the role of platelet-mast cell interactions in arterial thrombogenesis.
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PMID:Platelet activation responses in vitro to human mast cell activation. 1044 89

This review provides a survey on mast cell heterogeneity, with aspects differing in humans and rodents or which are subject of conflicting evidence being discussed in greater detail. Mast cell subsets have been first defined in rats by their fixation and dye-binding properties, and detailed studies in humans and pigs reveal very similar observations. The dye-binding properties of rat mast cell subsets are causally related to the absence or presence of heparin in their granules. In humans, this relation has not been shown. Rodent mast cell subsets store different chymase-isoforms. In contrast, just a single chymase has been defined in humans, and mast cells are classified by the presence or relative absence of this chymase. Different investigators find quite different proportions of chymase-positive to chymase-negative mast cells. Tryptase(s) are found in most or every human mast cell, but in rodents, they have hitherto been essentially localised to mast cells in connective tissues. Human mast cell subsets may also be defined by their expression of receptors such as C5aR and possibly the beta-chemokine receptor CCR3; the CCR3 expression seems to be related to the human mast cell chymase expression. Ultrastructural studies are helpful to distinguish human mast cell subsets, and allow to distinguish between chronic and acute activation. The phenotypical characteristics may change in association with inflammation or other disease processes. Studies in humans and pigs show changed dye-binding and fixation properties of the granules. Experimental rodent infection models reveal similar changes of chymase isoform expression. Human lung mast cells have been reported to strongly upregulate their chymase content in pulmonary vascular disease. This line of evidence can explain some inconsistent information on mast cell heterogeneity and may help to understand the physiological role of mast cells.
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PMID:Mast cell granule composition and tissue location--a close correlation. 1096 36

We induced the passive reverse Arthus reaction to IgG immune complexes (IC) at different tissue sites in mice lacking C3 treated or not with a C5aR-specific antagonist, or in mice lacking mast cells (Kit(W)/Kit(W-v) mice), and compared the inflammatory responses with those in the corresponding wild-type mice. We confirmed that IC inflammation of skin can be mediated largely by mast cells expressing C5aR and FcgammaRIII. In addition, we provided evidence for C3-independent C5aR triggering, which may explain why the cutaneous Arthus reaction develops normally in C3(-/-) mice. Furthermore, some, but not all, of the acute changes associated with the Arthus response in the lung were significantly more intense in normal mice than in C3(-/-) or Kit(W)/Kit(W-v) mice, indicating for C3- and mast cell-dependent and -independent components. Finally, we demonstrated that C3 contributed to the elicitation of neutrophils to alveoli, which corresponded to an increased synthesis of TNF-alpha, macrophage-inflammatory protein-2, and cytokine-induced neutrophil chemoattractant. While mast cells similarly influenced alveolar polymorphonuclear leukocyte influx, the levels of these cytokines remained largely unaffected in mast cell deficiency. Together, the phenotypes of C3(-/-) mice and Kit(W)/Kit(W-v) mice suggest that complement and mast cells have distinct tissue site-specific requirements acting by apparently distinct mechanisms in the initiation of IC inflammation.
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PMID:Distinct tissue site-specific requirements of mast cells and complement components C3/C5a receptor in IgG immune complex-induced injury of skin and lung. 1144 Nov 11

Depending on their stage of maturation and other factors, mast cell (MC) subsets differ from each other in terms of the expression of complement-associated antigens. This study analysed the expression of various complement-related cell surface antigens (CD11b/CR3, CD11c/CR4, CD35/CR1, CD55/DAF, CD59/MIRL, CD88/C5aR) on bone marrow mast cells (BMMC) in patients suffering from systemic mastocytosis (SM), other haematological diseases and non-haematological disorders (control groups). Expression of complement-associated cell surface antigens was analysed by flow cytometry. There were clear immunophenotypic differences between BMMC obtained from patients with SM and those from the control subjects: the percentage of patients expressing surface CD11c, CD35 and CD88 was significantly higher in patients with SM (76%, 100%, 54%) than in the control subjects (58%, 11%, 18%) (P < 0.05). In addition, the levels of CD11c, CD35 and CD88 expressed per MC (sites per cell) were significantly higher (P < 0.05) in SM than in the control group. Expression of the complement regulatory molecules CD55 and CD59 was detected in BMMC in all patients analysed. However, the levels of CD59 per BMMC were higher in patients with SM as compared with the control subjects, which could help to explain the formation of BMMC aggregates in the former group of individuals. Together, our results showed that BMMC in systemic mastocytosis overexpressed the cell surface membrane receptors involved in binding of complement components and complement-mediated cell activation. Whether this pathological expression of complement receptors is of pathophysiological significance remains to be determined.
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PMID:Overexpression of complement receptors and related antigens on the surface of bone marrow mast cells in patients with systemic mastocytosis. 1254 83


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