Human ecalectin, a variant of human galectin-9, is a novel eosinophil chemoattractant produced by T lymphocytes

A 1.6-kilobase pair cDNA was isolated from a human T-cell-derived expression library that encodes a novel eosinophil chemoattractant (designated ecalectin) expressed during allergic and parasitic responses. Based on its deduced amino acid sequence, ecalectin is a 36-kDa protein consisting of 323 amino acids. Although ecalectin lacks a hydrophobic signal peptide, it is secreted from mammalian cells. Ecalectin is not related to any known cytokine or chemokine but rather is a variant of human galectin-9, a member of the large family of animal lectins that have affinity for beta-galactosides. Recombinant ecalectin, expressed in COS cells and insect cells, exhibited potent eosinophil chemoattractant activity and attracted eosinophils in vitro and in vivo in a dose-dependent manner but not neutrophils, lymphocytes, or monocytes. The finding that the ecalectin transcript is present in abundance in various lymphatic tissues and that its expression increases substantially in antigen-activated peripheral blood mononuclear cells suggests that ecalectin is an important T-cell-derived regulator of eosinophil recruitment in tissues during inflammatory reactions. We believe that this is the first report of the expression of an immunoregulatory galectin expressed by a T-cell line that is selective for eosinophils.

Reversible expression of tryptases and chymases in the jejunal mast cells of mice infected with Trichinella spiralis

It is has been established that mouse mast cells (MCs) can reversibly alter their expression of serglycin proteoglycans and the homologous granule chymases that have been designated mouse MC protease (mMCP)-1, mMCP-2, and mMCP-5 in vivo. Nevertheless, it remained to be determined whether these immune cells could modify their expression of other chymases and the granule tryptases mMCP-6 and mMCP-7. As assessed immunohistochemically, we now show that MCs reversibly change their expression of the recently described chymase mMCP-9 and both tryptases as these cells traverse the jejunum during the amplification and regression stages of the reactive MC hyperplasia. In noninfected mice, most jejunal MCs reside in the submucosa and express mMCP-6 and mMCP-7, but not mMCP-9 or the chymase mMCP-2. During the inductive phase of the helminth-induced inflammation, when the jejunal MCs move from the submucosa to the tips of the villus, the MCs briefly express mMCP-9, cease expressing mMCP-6 and mMCP-7, and then express mMCP-2. During the recovery phase of the inflammation, jejunal MCs cease expressing mMCP-2 and then express varied combinations of mMCP-6, mMCP-7, and mMCP-9 as they move from the tips of the villus back toward the submucosa. In other model systems, mMCP-6 elicits neutrophil extravasation, and mMCP-7 regulates fibrin deposition and fibrinogen-mediated signaling events. Thus, the ability of a jejunal MC to reversibly alter its tryptase expression during an inflammatory event has important functional implications.

Induction of a selective and persistent extravasation of neutrophils into the peritoneal cavity by tryptase mouse mast cell protease 6

Recombinant mouse mast cell protease 6 (mMCP-6) was generated to study the role of this tryptase in inflammatory reactions. Seven to forty-eight hours after the i.p. injection of recombinant mMCP-6 into BALB/c, mast cell-deficient WCB6F1-Sl/Sl(d), C5-deficient, or mMCP-5-null mice, the number of neutrophils in the peritoneal cavity of each animal increased significantly by >50-fold. The failure of the closely related recombinant tryptase mMCP-7 to induce a comparable peritonitis indicates that the substrate specificities of the two tryptases are very different. Unlike most forms of acute inflammation, the mMCP-6-mediated peritonitis was relatively long lasting and neutrophil specific. Mouse MCP-6 did not induce neutrophil chemotaxis directly in an in vitro assay, but did promote chemotaxis of the leukocyte in the presence of endothelial cells. Mouse MCP-6 did not induce cultured human endothelial cells to express TNF-alpha, RANTES, IL-1alpha, or IL-6. However, the tryptase induced endothelial cells to express large amounts of IL-8 continually over a 40-h period. Neither enzymatically active mMCP-7 nor enzymatically inactive pro-mMCP-6 was able to induce endothelial cells to increase their expression of IL-8. Although the mechanism by which mMCP-6 induces neutrophil accumulation in tissues remains to be determined, the finding that mMCP-6 induces cultured human endothelial cells to selectively release large amounts of IL-8 raises the possibility that this tryptase regulates the steady state levels of neutrophil-specific chemokines in vivo during mast cell-mediated inflammatory events.

Expression and purification of enzymatically active recombinant granzyme B in a baculovirus system

Granzyme B (GranB), a serine protease stored in the granules of cytotoxic T lymphocytes and natural killer cells, can initiate target cell apoptosis. To produce large amounts of purified active enzyme, recombinant murine granzyme B (rGranB) was expressed from baculovirus in insect cells. The expressed rGranB is secreted into the culture medium and can be readily purified to homogeneity by one-step affinity chromatography to yield 1.5 mg enzyme per liter insect cell medium. RGranB is recognized by a GranB-specific anti-peptide antibody and is active against synthetic substrate Boc-Ala-Ala-Asp-SBzl with kinetic constant (kcat/Km 45,000 M-1s-1) comparable to purified human GranB, RGranB processes the caspase pro-CPP32 into its enzymatically active form and induces DNA fragmentation in isolated nuclei in the presence of cytosolic factors. The ability to express enzymatically active rGranB using the baculovirus system will help elucidate the role of this granzyme in the immune response.

The tryptase, mouse mast cell protease 7, exhibits anticoagulant activity in vivo and in vitro due to its ability to degrade fibrinogen in the presence of the diverse array of protease inhibitors in plasma

Mouse mast cell protease (mMCP) 7 is a tryptase of unknown function expressed by a subpopulation of mast cells that reside in numerous connective tissue sites. Because enzymatically active mMCP-7 is selectively released into the plasma of V3 mastocytosis mice undergoing passive systemic anaphylaxis, we used this in vivo model system to identify a physiologic substrate of the tryptase. Plasma samples taken from V3 mastocytosis mice that had been sensitized with immunoglobulin (Ig) E and challenged with antigen were found to contain substantial amounts of four 34-55-kDa peptides, all of which were derived from fibrinogen. To confirm the substrate specificity of mMCP-7, a pseudozymogen form of the recombinant tryptase was generated that could be activated after its purification. The resulting recombinant mMCP-7 exhibited potent anticoagulant activity in the presence of normal plasma and selectively cleaved the alpha-chain of fibrinogen to fragments of similar size as that seen in the plasma of the IgE/antigen-treated V3 mastocytosis mouse. Subsequent analysis of a tryptase-specific, phage display peptide library revealed that recombinant mMCP-7 preferentially cleaves an amino acid sequence that is nearly identical to that in the middle of the alpha-chain of rat fibrinogen. Because fibrinogen is a physiologic substrate of mMCP-7, this tryptase can regulate clot formation and fibrinogen/integrin-dependent cellular responses during mast cell-mediated inflammatory reactions.

Mouse mast cell protease 9, a novel member of the chromosome 14 family of serine proteases that is selectively expressed in uterine mast cells

Mouse mast cell protease (mMCP) 1, mMCP-2, mMCP-4, and mMCP-5 are members of a family of related serine proteases whose genes reside within an approximately 850 kilobase (kb) complex on chromosome 14 that does not readily undergo crossover events. While mapping the mMCP-1 gene, we isolated a novel gene that encodes a homologous serine protease designated mMCP-9. The mMCP-9 and mMCP-1 genes are only approximately 7 kb apart on the chromosome and are oriented back to back. The proximity of the mMCP-1 and mMCP-9 genes now suggests that the low recombination frequency of the complex is due to the closeness of some of its genes. The mMCP-9 transcript and protein were observed in the jejunal submucosa of Trichinella spiralis-infected BALB/c mice. However, in normal BALB/c mice, mMCP-9 transcript and protein were found only in those mast cells that reside in the uterus. Thus, the expression of mMCP-9 differs from that of all other chymases. The observation that BALB/c mouse bone marrow-derived mast cells developed with interleukin (IL) 10 and c-kit ligand contain mMCP-9 transcript, whereas those developed with IL-3 do not, indicates that the expression of this particular chymase is regulated by the cytokine microenvironment. Comparative protein structure modeling revealed that mMCP-9 is the only known granule protease with three positively charged regions on its surface. This property may allow mMCP-9 to form multimeric complexes with serglycin proteoglycans and other negatively charged proteins inside the granule. Although mMCP-9 exhibits a >50% overall amino acid sequence identity with its homologous chymases, it has a unique substrate-binding cleft. This finding suggests that each member of the chromosome 14 family of serine proteases evolved to degrade a distinct group of proteins.

The CT halo sign: a new finding in intestinal lymphangiectasia

A "halo sign" has been described in patients with Crohn disease, ulcerative colitis, radiation enteritis, ischemic colitis, and pseudomembranous colitis. This sign is characterized by an inner ring of low CT attenuation surrounded by a higher attenuation outer ring. We present a patient with primary intestinal lymphangiectasia in whom CT demonstrated a halo sign correlated with mucosal biopsy.

Mouse mast cells that possess segmented/multi-lobular nuclei

Because in humans mast cells and basophils tend to possess nonsegmented and segmented/multi-lobular nuclei, respectively, nuclear morphology has been a major criterion for assessing the lineage of metachromatic cells of hematopoietic origin. Immature metachromatic cells with mono- and multi-lobular nuclei were both obtained when bone marrow cells from BALB/c mice were cultured for 3 weeks in the presence of interleukin-3. Analogous to the indigenous mature mast cells that reside in the peritoneal cavity and skin, both populations of in vitro-derived cells expressed the surface receptor c-kit, the chymase mouse mast cell protease (mMCP) 5, the tryptase mMCP-6, and the exopeptidase carboxypeptidase A (mMC-CPA). Immunogold electron microscopy confirmed the granule location of mMC-CPA and mMCP-6 in both populations of cells, and cytochemical analysis confirmed the presence of chymotryptic enzymes in the granules. Because mature mast cells possessing multi-lobular nuclei also were occasionally found in the skeletal muscle and jejunum of the BALB/c mouse, the V3 mouse mast cell line was used to investigate the developmental relationship of mast cells that have very different nuclear structures. After the adoptive transfer of V3 mast cells into BALB/c mice, v-abl-immortalized mast cells with mono- and multi-lobular nuclei were detected in the lymph nodes and other tissues of the mastocytosis mice that expressed c-kit, mMCP-5, mMCP-6, and mMC-CPA. These studies indicate that mouse mast cells can exhibit varied nuclear profiles. Moreover, the nuclear morphology of this cell type gives no insight as to its protease phenotype or stage of development.

Glucocorticoids inhibit the cytokine-induced proliferation of mast cells, the high affinity IgE receptor-mediated expression of TNF-alpha, and the IL-10-induced expression of chymases

Mast cells are a heterogeneous family of immune cells that, when activated through their high affinity IgE receptors (Fc epsilonRI), release various granule mediators (e.g., neutral proteases and serglycin proteoglycans) and proinflammatory cytokines (e.g., IL-6 and TNF-alpha). We and others have shown that the growth and differentiation of immature, nontransformed mouse bone marrow-derived mast cells (mBMMC) can be regulated in vitro by IL-3, IL-10, and c-kit ligand. We now report that glucocorticoids inhibit the c-kit ligand- and IL-3-induced proliferation of mBMMC, the Fc epsilonRI-mediated expression of TNF-alpha, and the IL-10-mediated expression of the two chymases designated mouse mast cell protease (mMCP)-1 and mMCP-2. In contrast, glucocorticoids induce mBMMC to increase their expression of serglycin proteoglycan and carboxypeptidase A. As assessed by nuclear run-on and RNA blot analyses, dexamethasone inhibited the IL-10-mediated expression of mMCP-1 and mMCP-2, primarily by inducing rapid degradation of their transcripts. The stimulative effect on serglycin proteoglycan expression and the inhibitory effect on chymase expression were dose and time dependent and glucocorticoid specific. These findings indicate that glucocorticoids exert profound and diverse effects on the growth, cytokine expression, and granule differentiation of mouse mast cells, and that at least some of this regulation occurs through a post-transcriptional mechanism.

Glucocorticoids inhibit the cytokine-induced proliferation of mast cells, the high affinity IgE receptor-mediated expression of TNF-alpha, and the IL-10-induced expression of chymases

Mast cells are a heterogeneous family of immune cells that, when activated through their high affinity IgE receptors (Fc epsilonRI), release various granule mediators (e.g., neutral proteases and serglycin proteoglycans) and proinflammatory cytokines (e.g., IL-6 and TNF-alpha). We and others have shown that the growth and differentiation of immature, nontransformed mouse bone marrow-derived mast cells (mBMMC) can be regulated in vitro by IL-3, IL-10, and c-kit ligand. We now report that glucocorticoids inhibit the c-kit ligand- and IL-3-induced proliferation of mBMMC, the Fc epsilonRI-mediated expression of TNF-alpha, and the IL-10-mediated expression of the two chymases designated mouse mast cell protease (mMCP)-1 and mMCP-2. In contrast, glucocorticoids induce mBMMC to increase their expression of serglycin proteoglycan and carboxypeptidase A. As assessed by nuclear run-on and RNA blot analyses, dexamethasone inhibited the IL-10-mediated expression of mMCP-1 and mMCP-2, primarily by inducing rapid degradation of their transcripts. The stimulative effect on serglycin proteoglycan expression and the inhibitory effect on chymase expression were dose and time dependent and glucocorticoid specific. These findings indicate that glucocorticoids exert profound and diverse effects on the growth, cytokine expression, and granule differentiation of mouse mast cells, and that at least some of this regulation occurs through a post-transcriptional mechanism.

An unusual hernia: congenital pericardial effusion associated with liver herniation into the pericardial sac

To our knowledge there have been only two previous cases of diaphragmatic hernia into the pericardium diagnosed antenatally. We describe our pre- and post-natal radiological findings in such a case, although the final diagnosis eluded us until after delivery.

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.

Fate of two mast cell tryptases in V3 mastocytosis and normal BALB/c mice undergoing passive systemic anaphylaxis: prolonged retention of exocytosed mMCP-6 in connective tissues, and rapid accumulation of enzymatically active mMCP-7 in the blood

The mouse mast cell protease granule tryptases designated mMCP-6 and mMCP-7 are encoded by highly homologous genes that reside on chromosome 17. Because these proteases are released when mast cells are activated, we sought a basis for distinctive functions by examining their fates in mice undergoing passive systemic anaphylaxis. 10 min-1 h after antigen (Ag) was administered to immunoglobulin (Ig)E-sensitized mice, numerous protease/proteoglycan macromolecular complexes appeared in the extracellular matrix adjacent to most tongue and heart mast cells of normal BALB/c mice and most spleen and liver mast cells of V3 mastocytosis mice. These complexes could be intensively stained by anti-mMCP-6 Ig but not by anti-mMCP-7 Ig. Shortly after Ag challenge of V3 mastocytosis mice, large amounts of properly folded, enzymatically active mMCP-7 were detected in the plasma. This plasma-localized tryptase was approximately 150 kD in its multimeric state and approximately 32 kD in its monomeric state, possessed an NH2 terminus identical to that of mature mMCP-7, and was not covalently bound to any protease inhibitor. Comparative protein modeling and electrostatic calculations disclosed that mMCP-6 contains a prominent Lys/Arg-rich domain on its surface, distant from the active site. The absence of this domain in mMCP-7 provides an explanation for its selective dissociation from the exocytosed macromolecular complex. The retention of exocytosed mMCP-6 in the extracellular matrix around activated tissue mast cells suggests a local action. In contrast, the rapid dissipation of mMCP-7 from granule cores and its inability to be inactivated by circulating protease inhibitors suggests that this tryptase cleaves proteins located at more distal sites.

Post-transcriptional regulation of chymase expression in mast cells. A cytokine-dependent mechanism for controlling the expression of granule neutral proteases of hematopoietic cells

Although all mouse mast cells are derived from a common progenitor, these effector cells exhibit tissue-specific differences in their expression of the chymase family of serine proteases whose genes reside on chromosome 14. Immature bone marrow-derived mast cells (mBMMC), developed in vitro with interleukin (IL) 3-enriched medium, were cultured in the presence or absence of IL-10 to determine at the molecular level how the expression of the individual chymases is differentially regulated. As assessed by RNA blot analysis, mBMMC contain high steady-state levels of the transcript that encodes mouse mast cell protease (mMCP) 5, but not the homologous chymase transcripts that encode mMCP-1, mMCP-2, or mMCP-4. Nevertheless, nuclear run-on analysis revealed that these cells transcribe all four mast cell chymase genes. IL-10 elicited high steady-state levels of the mMCP-2 transcript, and pulse-chase experiments revealed that the half-life of the mMCP-2 transcript in mBMMC maintained in the presence of IL-10 is approximately 4-fold longer than that in replicate cells subsequently cultured in medium without IL-10. Reverse transcription-polymerase chain reaction/nucleotide sequence analysis demonstrated that mBMMC cultured in the absence or presence of IL-10 correctly process mMCP-2 pre-mRNA. Experiments with cycloheximide and actinomycin D indicated that IL-10 induces expression of a trans-acting factor(s) that stabilizes the mMCP-2 transcript or facilitates its processing. The discovery that the expression of certain chymases in mBMMC is regulated primarily at the post-transcriptional level provides a basis for understanding the mechanism by which specific cytokines dictate expression of the chromosome 14 family of serine proteases in cells that participate in inflammatory processes.

Natural disruption of the mouse mast cell protease 7 gene in the C57BL/6 mouse

The C57BL/6 mouse differs from the BALB/c mouse in that its ear and skin mast cells and its progenitor bone marrow-derived mast cells (mBMMCs) do not express mouse mast cell protease (mMCP) 7. We now report that, as detected by nuclear run-on analysis, the mMCP-7 gene is transcribed in C57BL/6 mBMMCs at a rate comparable to that in BALB/c mBMMCs. Reverse transcriptase-polymerase chain reaction analysis and sequencing of the product revealed that the ears of C57BL/6 mice contain small amounts of a mMCP-7 transcript that possesses a 98-base pair deletion. The deletion begins at a normally quiescent cryptic splice site (G416TGAG), 98 base pairs upstream of the normal exon 2/intron 2 splice site (G514TGAG), and introduces a premature stop codon in the alternatively spliced transcript. Thus, even if translated, the mature protein would consist of only 18 amino acids as compared to 245 amino acids in normal mMCP-7. Sequence analysis of the mMCP-7 gene in the C57BL/6 mouse revealed that the cryptic splice site is activated due to a G514-->A point mutation at the first nucleotide of the normal exon 2/intron 2 splice site. This is the first report of a mutation of a gene that encodes a mast cell secretory granule constituent that leads to its loss of expression. Moreover, the mMCP-7 gene is the first found in any species that sequentially has undergone a splice site mutation to cause retention of an intron and then a second splice site mutation to cause activation of a cryptic splice site.

Packaging of proteases and proteoglycans in the granules of mast cells and other hematopoietic cells. A cluster of histidines on mouse mast cell protease 7 regulates its binding to heparin serglycin proteoglycans

Mouse mast cell protease 7 (mMCP-7) is a tryptase stored in the secretory granules of mast cells. At the granule pH of 5.5, mMCP-7 is fully active and is bound to heparin-containing serglycin proteoglycans. to understand the interaction of mMCP-7 with heparin inside and outside the mast cell, this trytase was first studied by comparative protein modeling. The "pro" form of mMCP-7 was then expressed in insect cells and studied by site-directed mutagenesis. Although mMCP-7 lacks known linear sequences of amino acis that interact with heparin, the three-dimensional model of mMCP-7 revealed an area on the surface of the folded protein away from the substrate-binding site that exhibits a strong positive electrostatic potential at the acidic pH of the granule. In agreement with this calculation, recombinant pro-mMCP-7 bound to a heparin-affinity column at pH 5.5 and readily dissociated from the column at pH > 6.5. Site-directed mutagenesis confirmed the prediction that the conversion of His residues 8,68, and 70 in the positively charged region into Glu prevents the binding of pro-mMCP-7 to heparin. Because the binding requires positively charged His residues, native mMCP-7 is able to dissociate from the protease/proteoglycan macromolecular complex when the complex is exocytosed from bone marrow-derived mast cells into a neutral pH environment. Many hematopoietic effector cells store positively charged proteins in granules that contain serglycin proteoglycans. The heparin/mMCP-7 interaction, which depends on the tertiary structure of the tryptase, may be representative of a general control mechanism by which hematopoietic cells maximize storage of properly folded, enzymatically active proteins in their granules.

Tissue-regulated differentiation and maturation of a v-abl-immortalized mast cell-committed progenitor

An immature v-abl-transformed mast cell line (V3-MC) was derived from a mouse that developed systemic mastocytosis after transplantation of v-abl-infected bone marrow cells. V3-MCs injected intravenously into adult BALB/c mice infiltrated the liver, spleen, and intestine by day 6 and underwent progressive differentiation and maturation, eventually resembling indigenous mast cells. In terms of their protease content, the V3-MCs that localized in the liver and spleen differed from those in the intestine, and both differed from the cultured V3-MCs. The acquired expression of certain proteases and the loss of expression of other proteases in these tissue V3-MCs defines particular phenotypes and indicates that the differentiation and maturation of mast cell-committed progenitor cells are primarily regulated by factors in the different tissue microenvironments.

Inflammatory effector mechanisms in asthma

Each of these effector systems has the capacity to initiate airway obstruction or alter airway responsiveness in asthma. It is likely that they act in concert in certain asthmatic settings. Further basic and applied research will define their relative roles in asthma.

An assessment of Ryan White Title IIIb HIV early intervention programs in Region VI of the United States Public Health Service

A survey was conducted of 15 early intervention programs in Region VI of the United States Public Health Service (USPHS) to determine when human immunodeficiency virus (HIV)-infected clients assessed care. Data were collected from 672 HIV-infected patients who received medical care between March 1991 and July 1993. Eighty-four percent were male, 42% were white, 35% were African-American, 22% were Hispanic, and less than 1% defined themselves as "other." Information also was obtained on HIV risk factors and CD4 counts on entry to the facility. Thirty percent of patients had entry CD4 counts > 500/mm3, 55% had counts between 499 and 200/mm3, and 25% < 200/mm3. The distribution of entry CD4 counts were similar to those reported from two large, urban, public-hospital HIV clinics. The most common risk factor for all ethnicities was male-to-male sex (53%), followed by heterosexual exposure (17%), and injection drug use (16%). The results indicate that the majority of clients who initially present to Title IIIb "early intervention" programs in Region VI are of ethnic minority groups. Based on entry CD4 counts, patients in Title IIIb programs present late with one fourth at acquired immunodeficiency syndrome (AIDS)-defining levels. Regardless of ethnicity, male-to-male sex was the highest risk factor in this region. These findings have significant implications for the targeting of specific populations for outreach and for possibly reallocating funds for future planning of Ryan White Comprehensive AIDS Emergency Care Act programs.

Lack of expression of the tryptase mouse mast cell protease 7 in mast cells of the C57BL/6J mouse

Although the steady-state level of the mouse mast cell protease (mMCP) 7 transcript is below detection in the serosal and mucosal mast cells of the BALB/cJ mouse, the IL-3-dependent, bone marrow-derived mast cells (mBMMC) of this strain and four other strains contain a high steady-state level of the mMCP-7 transcript. To further analyze the expression of this mast cell tryptase, a mMCP-7-specific IgG was obtained by immunizing a rabbit with a 19-residue synthetic peptide that corresponds to its unique amino acid sequence at residues 160 to 178 (anti-mMCP-7(160-178). In a SDS-PAGE/immunoblot analysis of lysates of BALB/cJ mBMMC, anti-mMCP-7(160-178) IgG recognized a diffuse 31- to 36-kDa protein, which shifted to a sharp 27-kDa protein after treatment with N-glycanase. As assessed immunohistochemically, mMCP-7 protein is present not only in the secretory granules of BALB/cJ mBMMC, but also in the ear mast cells of this strain. In contrast, the ear mast cells of the C57BL/6J mouse do not contain detectable levels of mMCP-7 protein, although the ear mast cells of both mouse strains contain mMCP-5 protein. Because mMCP-7 mRNA and protein also were not detected in mBMMC from the C57BL/6J mouse, the failure of the ear mast cells of this strain to express mMCP-7 is most likely a consequence of an intrinsic abnormality in the mast cell-committed progenitor cells themselves, or in the bone marrow microenvironment that induces its mast cell progenitor cells to express this tryptase.

Lack of expression of the tryptase mouse mast cell protease 7 in mast cells of the C57BL/6J mouse

Although the steady-state level of the mouse mast cell protease (mMCP) 7 transcript is below detection in the serosal and mucosal mast cells of the BALB/cJ mouse, the IL-3-dependent, bone marrow-derived mast cells (mBMMC) of this strain and four other strains contain a high steady-state level of the mMCP-7 transcript. To further analyze the expression of this mast cell tryptase, a mMCP-7-specific IgG was obtained by immunizing a rabbit with a 19-residue synthetic peptide that corresponds to its unique amino acid sequence at residues 160 to 178 (anti-mMCP-7(160-178). In a SDS-PAGE/immunoblot analysis of lysates of BALB/cJ mBMMC, anti-mMCP-7(160-178) IgG recognized a diffuse 31- to 36-kDa protein, which shifted to a sharp 27-kDa protein after treatment with N-glycanase. As assessed immunohistochemically, mMCP-7 protein is present not only in the secretory granules of BALB/cJ mBMMC, but also in the ear mast cells of this strain. In contrast, the ear mast cells of the C57BL/6J mouse do not contain detectable levels of mMCP-7 protein, although the ear mast cells of both mouse strains contain mMCP-5 protein. Because mMCP-7 mRNA and protein also were not detected in mBMMC from the C57BL/6J mouse, the failure of the ear mast cells of this strain to express mMCP-7 is most likely a consequence of an intrinsic abnormality in the mast cell-committed progenitor cells themselves, or in the bone marrow microenvironment that induces its mast cell progenitor cells to express this tryptase.

Mouse bone marrow-derived mast cells (mBMMC) obtained in vitro from mice that are mast cell-deficient in vivo express the same panel of granule proteases as mBMMC and serosal mast cells from their normal littermates

The ear, skin, and purified serosal mast cells of WBB6F1/J-(+/+) (WB-(+/+)) and WCB6F1/J-(+/+) (WC-(+/+)) mice contain high steady-state levels of the transcripts that encode mouse mast cell protease (mMCP) 2, mMCP-4, mMCP-5, mMCP-6, and mouse mast cell carboxypeptidase A (mMC-CPA). In contrast, no mast cell protease transcripts are present in abundance in the ear and skin of WBB6F1/J-W/Wv (W/Wv) and WCB6F1/J-Sl/Sld (Sl/Sld) mice which are mast cell-deficient in vivo due to defects in their c-kit and c-kit ligand genes, respectively. We now report that the immature bone marrow-derived mast cells (mBMMC) obtained in vitro with recombinant interleukin 3 (rIL-3) or WEHI-3 cell conditioned medium from WB-(+/+), WC-(+/+), W/Wv, and Sl/Sld mice all contain high steady-state levels of the mMCP-2, mMCP-4, mMCP-5, mMCP-6, and mMC-CPA transcripts. As assessed immunohistochemically, mMCP-2 protein and mMCP-5 protein are also present in the granules of mBMMC from WB-(+/+), WC-(+/+), and W/Wv mice. That Sl/Sld and W/Wv mBMMC contain high steady-state levels of five granule protease transcripts expressed by the mature serosal, ear, and skin mast cells of their normal +/+ littermates suggests that c-kit-mediated signal transduction is not essential for inducing transcription of these protease genes. Because rIL-4 inhibits the rIL-10-induced expression of mMCP-1 and mMCP-2 in BALB/cJ mBMMC, the ability of rIL-4 to influence protease mRNA levels in WC-(+/+) mBMMC and W/Wv mBMMC was investigated. Although rIL-10 induced expression of the mMCP-1 transcript in WC-(+/+) and W/Wv mBMMC, rIL-4 was not able to suppress the steady-state levels of the mMCP-1 transcript or any other protease transcript in these cultured mast cells. Thus, not only do BALB/cJ mBMMC express fewer granule proteases than mBMMC from mast cell-deficient strains and their normal littermates but the subsequent induction of late-expressed proteases in BALB/cJ mBMMC is more tightly regulated by IL-3 and IL-4.

Strain-specific and tissue-specific expression of mouse mast cell secretory granule proteases

As assessed by RNA blot analyses with gene-specific probes, we report that the perivascular connective tissue mast cells (CTMCs) in the ear and skin of BALB/cJ mice contain abundant levels of the mouse mast cell protease (mMCP) 7 transcript, in addition to those protease transcripts present in their serosal mast cells (SMCs). High levels of the mMCP-7 transcript also were detected in the ears of WBB6F1/J(-)+/+, WCB6F1/J(-)+/+, WB/ReJ(-)+/+, and WC/ReJ(-)+/+ mice. However, the ears of these four strains and the SMCs from the WCB6F1/J(-)+/+ strain but not the BALB/cJ strain also contained high steady-state levels of the mMCP-2 transcript. The mMCP-2, mMCP-4, mMCP-5, mMCP-6, and mMCP-7 transcripts were not detected in the ears of mast-cell-deficient WBB6F1/J-W/Wv and WCB6F1/J-Sl/Sld mice, indicating that mast cells were the source of these protease transcripts in the +/+ animals. When immunohistochemical analyses of serial sections of ear and skin from WBB6F1/J(-)+/+ mice were performed with anti-mMCP-2 IgG and anti-mMCP-5 IgG, the perivascular CTMCs in these tissues were found to express both mMCP-2 and mMCP-5 in their granules. The prominent expression of mMCP-7 in constitutive perivascular CTMCs indicates that this mast cell has an extended protease phenotype relative to the SMCs of the same strains. Further, the perivascular CTMCs and SMCs of the +/+ strains differ from those in BALB/cJ mice in their prominent expression of mMCP-2.