Biomedical subjects

G F Newlands

Publications and source records attributed to G F Newlands.

At least 37 records · Page 2Linked to original sources

PubMed1995

Release of the mucosal mast cell granule chymase, rat mast cell protease-II, during anaphylaxis is associated with the rapid development of paracellular permeability to macromolecules in rat jejunum.

The soluble granule chymase, rat mast cell protease-II (RMCP-II), is abundantly expressed in intestinal mucosal mast cells (MMC) but its function is not known. One hypothesis is that RMCP-II degrades the epithelial basement membrane and promotes the loss of enterocytes typically associated with type I hypersensitivity reactions in the rat. To test this hypothesis more directly, ex vivo perfusion of the cranial mesenteric artery and jejunal lumen was used to monitor the anaphylactic release of RMCP-II and its effects on mucosal permeability and epithelial integrity. Within 2 min of intravascular challenge with soluble adult Nippostrongylus brasiliensis worm antigen there was a 1,000-fold (P < 0.02) increase in the concentration of RMCP-II in the vascular perfusate from the jejunum of Nippostrongylus-sensitized rats but not the controls. Similarly, translocation of RMCP-II into the gut lumen increased 10-fold (P < 0.02) after 2 min only in worm antigen-challenged immune rats. Using an identical protocol, but incorporating Evans blue-labeled human serum albumin (EB-HSA) in the vascular perfusate, the timing of the release of RMCP-II into the two compartments was very similar to the first experiment and furthermore the translocation of EB-HSA increased 18-fold (P < 0.05) after 4 min in sensitized rats challenged with worm antigen. To examine the effects of RMCP-II more directly 1 mg of the highly purified chymase was introduced into the cranial mesenteric artery in ex vivo perfused normal rats. A significant (P < 0.05) 70-fold increase in concentration of RMCP-II in jejunal perfusate occurred after 6 min. In a repeat dose-response experiment, infusion of 0.375, 0.75, or 1.5 mg of RMCP-II, together with EB-HSA, established that the cumulative amounts of RMCP-II and EB-HSA translocated from the vasculature to the gut lumen in each perfusion (during the 10-min period of RMCP-II infusion) were significantly correlated. Analysis of intestinal perfusates by SDS-PAGE and by Western blotting using monoclonal anti-RMCP-II antibody confirmed that there was a concomitant translocation of both the protease and EB-HSA into the gut lumen. Histological evaluation of the mucosa failed to reveal any significant morphological change in any of the experiments. The rapid development of macromolecular leak, its association with the translocation of RMCP-II, and the absence of gross epithelial lesions, suggest for the first time that a mast cell granule chymase increases epithelial permeability via a paracellular route and implies that the substrate may be a protein, or proteins, in the epithelial junctional complex.

Anaphylaxis↗

PubMed1995

Stem cell factor contributes to intestinal mucosal mast cell hyperplasia in rats infected with Nippostrongylus brasiliensis or Trichinella spiralis, but anti-stem cell factor treatment decreases parasite egg production during N brasiliensis infection.

We assessed the effects of the c-kit ligand, stem cell factor (SCF), in the jejunal mucosal mast cell hyperplasia that occurs during infection with the intestinal nematodes, Nippostrongylus brasiliensis or Trichinella spiralis in rats. Compared with vehicle-treated rats, rats treated with SCF (25 micrograms/kg/d, intravenous [i.v.] for 14 days) during N brasiliensis infection exhibited significantly higher levels of the rat mucosal mast cell (MMC)-associated protease, rat mast cell protease II (RMCP II) in the jejunum and serum on day 8 of infection, but not on days 10 or 15 of infection. By contrast, in comparison to rats treated with normal sheep IgG, rats treated with a polyclonal sheep antirat SCF antibody exhibited markedly decreased numbers of jejunal MMCs, levels of jejunal RMCP II, and serum concentrations of RMCP II during infection with either nematode, particularly at the earlier intervals of infection (< or = day 10). Taken together, these findings indicate that SCF importantly contributes to MMC hyperplasia and/or survival during N brasiliensis or T spiralis infection in rats, but that levels of endogenous SCF are adequate to sustain near maximal MMC hyperplasia during infection with these nematodes. Notably, treatment of rats with SCF somewhat increased, and treatment with anti-SCF significantly decreased, parasite egg production during N brasiliensis infection. This finding raises the interesting possibility that certain activities of intestinal MMCs may contribute to parasite fecundity during infection with this nematode.

Analysis of Variance↗

PubMed1995

Activation of precursors for matrix metalloproteinases 1 (interstitial collagenase) and 3 (stromelysin) by rat mast-cell proteinases I and II.

Histological studies have previously demonstrated an association between mast-cell activation/degranulation and areas of connective-tissue lysis in vivo; in addition, mast-cell extracts have been shown to activate latent forms of collagenase and stromelysin. In the present study we have examined the potential roles of rat mast-cell proteinase (RMCP) I and RMCP II as activators of the precursors of matrix metalloproteinase (MMP)-1 (interstitial collagenase), MMP-2 (gelatinase A) and MMP-3 (stromelysin 1). Both RMCPs I and II activated proMMP-3 by converting the 57 kDa precursor into a 45 kDa polypeptide. The N-terminal amino acid of 45 kDa MMP-3 activated by RMCP II was identified as Phe83. By contrast, only RMCP II activated the 52 kDa proMMP-1 by converting it into a 41 kDa protein and generating the new N-termini, namely Gln80 and Val82. The collagenolytic activity which resulted from this cleavage was only 35% of the full activity, but this could not be augmented by subsequent treatment with MMP-3, the latter being a crucial enzyme for the generation of the fully active MMP-1 with Phe81 at the N-terminus, in conjunction with other serine proteinases. Thus RMCP II activates proMMP-1 via a mechanism different from that reported for the stepwise processing by combinations of other trypsin-like enzymes and MMP-3. ProMMP-2 (pro-gelatinase A) was not activated by either RMCP I or RMCP II, despite processing to smaller products.

Amino Acid Sequence↗

PubMed1995

Stem cell factor dependent hyperplasia of mucosal-type mast cells but not eosinophils in Schistosoma mansoni-infected rats.

Stem cell factor (SCF) is a growth factor with multiple activities which acts on numerous cell types including primordial germ cells, haemopoietic stem cells, melanocytes and mast cells. SCF is critical for the development of the mast cell hyperplasia associated with infection with the intestinal parasites Nippostrongylus brasiliensis and Trichinella spiralis. In the present study we have assessed the role of SCF in the mast cell and eosinophil responses to Schistosoma mansoni in the rat by blocking its effects in vivo with polyclonal antibody to SCF. Rats treated with sheep anti-SCF antibody on days 21, 24, 27 and 30 of infection with S. mansoni showed a rapid decrease in serum concentrations of the mucosal mast cell-associated protease rat mast cell protease II (RMCP II) by day 24, compared with normal sheep IgG-treated controls. Similarly, the number of mucosal mast cells and RMCP II levels in both small intestine and liver were also significantly reduced by day 32 of infection. In contrast with the depeletion of mast cells and mast cell proteases, eosinophil numbers in liver or intestine did not change significantly after anti-SCF treatment compared with controls. These results confirm that mast cell survival and hyperplasia are dependent on the presence of SCF whilst demonstrating that the eosinophil recruitment to liver and intestine associated with S. mansoni infection is SCF-independent.

Animals↗

PubMed1995

Basal secretion and anaphylactic release of rat mast cell protease-II (RMCP-II) from ex vivo perfused rat jejunum: translocation of RMCP-II into the gut lumen and its relation to mucosal histology.

The kinetics of the release of rat mast cell protease-II (RMCP-II) from mucosal mast cells in the jejunum of Nippostrongylus brasiliensis primed (immune) rats was investigated using ex vivo perfusion of a segment of jejunum through the cranial mesenteric artery. The aim of the study was to assess the role of the protease in anaphylaxis and in particular to ascertain whether it is responsible for the histological changes, which include widespread epithelial shedding, seen in the mucosa in in vivo models of anaphylaxis. Perfusion of the jejunal vasculature with a Krebs-Ringer buffer showed that there was basal secretion of RMCP-II by jejunal mast cells in all rats studied. The baseline concentration of RMCP-II was significantly greater (p < 0.05) in immune rats (> 7 ng/ml) previously exposed to nippostrongylus infection than in control, naive animals (< 2 ng/ml). Challenge of immune rats with 100 or 400 worm equivalents of whole worm antigen resulted in an immediate (within 40 seconds) and significant (p < 0.02) increase in the concentration of RMCP-II (to > 3 micrograms/ml) in the vascular perfusate, which was not seen in naive rats or immune rats challenged with an irrelevant antigen. Greater amounts of RMCP-II were also recovered from the jejunal lumen of immune rats compared with naive rats after challenge of both groups with worm antigen. Despite the release of microgram quantities of RMCP-II into the gut lumen and vascular perfusate, however, there were no significant changes seen in the mucosal histology. These results suggest that RMCP-II alone is not responsible fore the loss of gut epithelium seen during anaphylaxis in the rat.

Anaphylaxis↗

PubMed1995

Response of mucosal mast cells to intestinal ischemia-reperfusion injury in the rat.

The goals of this study were to investigate the in vivo effects of intestinal ischemia-reperfusion on mucosal mast cells, and to evaluate the morphological changes induced by standardized arterial occlusion in anesthetized rats. Complete segmental ileal ischemia was maintained for 15, 30, or 60 min, and was followed by a 30 min reperfusion period. Intestinal biopsies taken at the end of ischemia and in the 30th min of reperfusion were evaluated by image analysis, and the rate of release of type II rat mast cell protease, a marker of mast cell exocytosis, was determined from the venous effluent of the segment. Electron microscopy revealed cytoplasmic vacuolization of the mast cells of the villi after the 15 min ischemia. Ischemia induced a continuous diminution of the mucosal thickness and a significant fall in the number of mast cells in the villi; with immunoperoxidase staining with a monoclonal antibody that recognizes the AD1 mast cell surface antigen, the decrease was 57, 49, and 66% in the 15, 30, and 60 min ischemia groups, respectively. In these groups, the mucosal type II mast cell protease concentration increased to 2.4-, 2.5-, and 3.6-fold, respectively, and a significant increase in plasma protease levels was observed on reperfusion. These results lead us to conclude that mucosal mast cells are very sensitive to intestinal ischemia, with the majority of mast cells in the ileal villi already involved in the response to ischemia after a short period of arterial occlusion.

Animals↗

PubMed1994

Characterization of cultured mast cells derived from Ws/Ws mast cell-deficient rats with a small deletion at tyrosine kinase domain of c-kit.

The Ws mutant allele of rats represents a 12-base deletion at the tyrosine kinase domain of the c-kit gene. Although homozygous Ws/Ws rats were deficient in both connective tissue-type mast cells (CTMC) and mucosal-type mast cells (MMC), mast cells did develop when bone marrow cells of Ws/Ws rats were cultured in the presence of concanavalin A-stimulated spleen cell conditioned medium (ConA-SCM). Although the proliferative response of rat cultured mast cells (RCMC) derived from Ws/Ws rats to ConA-SCM was comparable to that of RCMC derived from control normal (+/+) rats, the proliferative response of Ws/Ws RCMC to rat recombinant stem cell factor (rrSCF; a ligand for the c-kit receptor tyrosine kinase) was much lower than that of +/+ RCMC. However, a slight c-kit kinase activity was detectable in Ws/Ws RCMC, and the proliferation of Ws/Ws RCMC was accelerated when rrSCF was added to ConA-SCM. Because CTMC contain rat mast cell protease-I (RMCP-I) and MMC contain RMCP-II, the phenotype of +/+ and Ws/Ws RCMC in various culture conditions was evaluated by immunohistochemistry of RMCPs. Both +/+ and Ws/Ws RCMC showed the MMC-like phenotype (RMCP-I-/II+) when they were cultured with ConA-SCM alone. Most +/+ RCMC and about half of Ws/Ws RCMC acquired a novel protease (RMCP-I+/II+) phenotype when they were cultured with rrSCF alone. However, because the number of Ws/Ws RCMC dropped to one-tenth in the medium containing rrSCF alone, the absolute number of Ws/Ws RCMC with the RMCP-I+/II+ phenotype did not increase significantly. The effect of rrSCF in inducing the novel phenotype was suppressed when ConA-SCM was added to rrSCF. In contrast, +/+ and Ws/Ws RCMC cocultured with +/+ fibroblasts showed the RMCP-I+/II+ phenotype even in the presence of ConA-SCM. Moreover, a fibroblast cell line derived from SI/SI mouse embryos that did not produce SCF did not support the survival of both +/+ and Ws/Ws RCMC but did induce the RMCP-I+/II+ phenotype in about half of +/+ and Ws/Ws RCMC when their survival was supported by the addition of ConA-SCM. The normal signal transduction through the c-kit receptor did not appear to be prerequisite for the acquisition of the RMCP-I+/II+ phenotype.

Animals↗

PubMed1994

Effects of stem cell factor (kit-ligand) and interleukin-3 on the growth and serine proteinase expression of rat bone-marrow-derived or serosal mast cells.

The effects of rat stem-cell factor (SCF) and interleukin-3 (IL-3), alone or in combination, on the in vitro growth and serine proteinase expression of rat serosal/connective-tissue mast cells (CTMC) or bone marrow-derived mast cells (BMMC) were examined. Rat SCF stimulated the growth of both CTMC and BMMC. IL-3 stimulated BMMC growth to a lesser extent than did SCF, whereas CTMC numbers did not increase in IL-3. However, SCF and IL-3 had synergistic effects on the growth of both BMMC and CTMC. SCF favoured the maintenance of rat mast cell proteinase-I (RMCP-I) in CTMC, but did not induce detectable production of RMCP-I in BMMC. In contrast, when IL-3 or lymph node-conditioned medium (LNCM) was added to SCF, a subpopulation of CTMC expressed and stored the soluble proteinase RMCP-II. In BMMC, the RMCP-II content of cells maintained in SCF was significantly less than that of cells maintained in IL-3 or LNCM. RMCP-II also appeared in the supernatants of BMMC, especially when BMMC numbers were increasing rapidly in SCF with or without IL-3 or LNCM. Thus, SCF and IL-3 can regulate the growth of rat BMMC and CTMC, as well as influence their production and release of proteinases.

Animals↗

PubMed1994

Fasting or dexamethasone treatment reduce protease content in rat lung mast cells and modulation of histamine synthesis by H3 receptors.

The sensitivity of mast cells to H3-receptor modulation was studied in rat lung under various hormonal conditions. The heterogeneity of mast cell sub-populations in rat lung was assessed by the tissue content of rat mast cell protease I (RMCP I) and rat mast cell protease II (RMCP II). After 24 h fasting, concentrations of RMCP I were unchanged whereas the concentration of RMCP II was significantly reduced by 49%. The [3H]histamine (HA) synthesis was concomitantly decreased by 35%. In addition, the modulation of [3H]HA synthesis by the H3 receptor agonist, (R)alpha-methylHA and by the antagonist, thioperamide, observed in control rats, was lost in fasted rats. Single and repeated administrations of dexamethasone did not influence RMCPI concentrations, but decreased the concentrations of RMCP II with a parallel decrease in [3H]HA synthesis. The inhibitory effect of (R)alpha-methylHA on [3H]HA synthesis was also reduced. These results suggest that a subpopulation of RMCP II-containing mast cells, very sensitive to environmental factors, could be the mast cells synthesizing HA in an H3-receptor-dependent manner.

Animals↗

PubMed1994

Hepatic recruitment of mast cells occurs in rats but not mice infected with Schistosoma mansoni.

The pathogenesis of infection with Schistosoma mansoni in rats is distinct from that in mice. Rats are non-permissive hosts and infection is terminated in the liver before egg laying commences whereas the parasites completes its life cycle in mice. Comparison of the mast cell responses in the two species reveals that a pronounced hepatic mastocytosis occurs in the rat and this is concomitant with the demise of the parasite. The majority of recruited hepatic mast cells contain the highly soluble granule chymase, rat mast cell protease-II, which is released systemically into blood during the period of parasite elimination. In contrast, very few mast cells are found in livers of parasitized mice and none contain the soluble granule chymase mouse mast cell protease-1. However, during egg deposition in the gut, an intraepithelial mastocytosis occurs in parasitized mice. These intraepithelial cells are typical mucosal mast cells as determined by their content of mouse mast cell protease-1. Recruitment of mucosal mast cells occurs in the intestinal lamina propria of infected rats soon after the parasites migrate to the liver. These findings suggest that mast cells of the mucosal phenotype are involved in the pathogenesis of the hepatic response to infection in the rat but that, in the mouse, mucosal mastocytosis is associated with intestinal sensitization by egg antigens.

Animals↗

PubMed1993

Biochemical and immunological characterization of multiple glycoforms of mouse mast cell protease 1: comparison with an isolated murine serosal mast cell protease (MMCP-4).

Five highly soluble, chymotrypsin-like, neutral serine proteases, with molecular masses in the range 30-33 kDa, were isolated from Trichinella spiralis-infected mouse small intestine. These enzymes were closely related antigenically on Western blotting and by Ouchterlony double diffusion using a polyclonal, cross-absorbed, sheep antibody raised against mouse mast cell protease-1 (MMCP-1) and on the basis of N-terminal amino acid sequence analysis, were identified as variant forms of MMCP-1. Substrate and inhibitor analysis confirmed that the five variants (MMCP-1 A-E) had similar characteristics, although highly significant (P = 0.025 to P < 0.0001) variations in Km and kcat, were detected. Against human alpha 1-proteinase inhibitor the Ki for MMCP-1C (45 pM) was significantly (P < 0.0001) greater than those for the other proteases (0.76-2.2 pM). The differences in electrophoretic mobility are probably a result of variable glycosylation, since removal of N-linked carbohydrate produced a polypeptide of approx. 28 kDa in each case which was, like the native enzyme, immunoreactive on Western blotting. A much less soluble 28 kDa enzyme was isolated from serosal mast cells and identified as MMCP-4 by N-terminal amino acid sequencing. Like MMCP-1 it has chymotrypsin-like substrate specificities with activity at neutral pH. However, it was antigenically distinct from MMCP-1 and, using sheep anti-MMCP-1, was not detected on Western blotting or by Ouchterlony double diffusion, e.l.i.s.a. or immunohistochemistry. This last technique established that the MMCP-1 variants were uniquely present in enteric mast cells, thereby providing a highly selective means of distinguishing the mucosal and connective tissue mast cell subsets in the mouse.

Amino Acid Sequence↗

PubMed1993

Infection of Nippostrongylus brasiliensis induces normal increase of basophils in mast cell-deficient Ws/Ws rats with a small deletion at the kinase domain of c-kit.

All basophils, mucosal-type mast cells (MMC) and connective tissue-type mast cells (CTMC) are derived from the multipotential hematopoietic stem cell. Mutations at the c-kit locus resulted in deficiency of MMC and CTMC in both mice and rats. To investigate the role of the c-kit receptor tyrosine kinase for production of basophils, we used white spotting/white spotting (Ws/Ws) mutant rats that have a small deletion at the tyrosine kinase domain of the c-kit gene. When Ws/Ws, nude athymic, and normal (+/+) rats were infected with Nippostrongylus brasiliensis (NB), the number of basophils increased greater than 50-fold in the peripheral blood of Ws/Ws and +/+ rats but did not increase in that of nude rats. Blood histamine concentration increased significantly in Ws/Ws and +/+ rats but did not increase in nude rats. Immature basophils increased greater than 10-fold in the bone marrow of Ws/Ws and +/+ rats but did not increase in that of nude rats. Mature and immature basophils that developed after the NB infection were identified by electron microscopy. The present result confirms that T-cell-derived cytokines are indispensable for the augmented production of basophils and suggests that stimulation via the c-kit receptor may not be necessary for the augmented production.

Animals↗

PubMed1993

Infection of Nippostrongylus brasiliensis induces development of mucosal-type but not connective tissue-type mast cells in genetically mast cell-deficient Ws/Ws rats.

Ws/Ws rats have a small deletion at the tyrosine kinase domain of the c-kit gene and are deficient in both mucosal mast cells (MMC) and connective tissue-type mast cells (CTMC). The role of the c-kit receptor in the development of MMC and CTMC was investigated by infecting Ws/Ws and control +/+ rats with Nippostrongylus brasiliensis (NB), which induces T-cell-dependent mast cell proliferation. Although mast cells did not develop in the skin of Ws/Ws rats, a significant number of mast cells developed in the jejunum after NB infection. These mast cells had the MMC protease phenotype (rat mast cell protease [RMCP] I-/II+) and lacked heparin because they were not stained with berberine sulfate. Globule leukocytes were also detected in the mucosal epithelium of these rats. However, the number of MMC and the serum concentration of RMCP II in NB-infected Ws/Ws rats were only 13% and 7% of those of NB-infected +/+ rats, respectively. A small number of mast cells also developed in the lung, liver, and mesenteric lymph nodes of Ws/Ws rats after NB infection. Although mast cells in these tissues had the MMC phenotype throughout the observation period, the increased mast cells in the lung and liver of +/+ rats acquired a CTMC-like phenotype and were RMCP I+/II+, berberine sulfate+, and formalin resistant. These results indicate that the need for the stimulus through the c-kit receptor appears to be greater in the development of CTMC in the skin as well as for CTMC-like mast cells in the lung and liver than for the development of MMC.

Animals↗

PubMed1992

The influence of challenge dose, duration of immunity, or steroid treatment on mucosal mast cells and on the distribution of sheep mast cell proteinase in Haemonchus-infected sheep.

The distribution of granule-specific sheep mast cell proteinase (SMCP), was assayed by immunocytochemistry and quantified by immunoassay in sheep immune to Haemonchus contortus. Repeated infection with Haemonchus larvae over 10-12 weeks induced a pronounced mucosal mastocytosis, including intraepithelial globule leukocytes (GL), which, 7 days after ceasing this dosing regime, was associated with the inability of incoming larvae to establish within the abomasal mucosa. Loss of this resistance, due to the cessation of stimulation with Haemonchus larvae 84 days previously or to treatment of sheep with corticosteroid, was associated with a marked decline in mast cell density and concentrations of SMCP in abomasal mucosal tissues. Nevertheless, larvae also failed to establish in immune sheep rested from challenge 42 days previously and in which mast cell counts were not significantly different from those of control sheep. A small, but significant, release of SMCP was demonstrated in gastric mucus from immune sheep following larval challenge, whereas little or no SMCP was detected in mucus from naïve animals.

Abomasum↗

PubMed1991

The rat c-kit ligand, stem cell factor, induces the development of connective tissue-type and mucosal mast cells in vivo. Analysis by anatomical distribution, histochemistry, and protease phenotype.

Mast cell development is a complex process that results in the appearance of phenotypically distinct populations of mast cells in different anatomical sites. Mice homozygous for mutations at the W or S1 locus exhibit several phenotypic abnormalities, including a virtual absence of mast cells in all organs and tissues. Recent work indicates that W encodes the c-kit tyrosine kinase receptor, whereas S1 encodes a c-kit ligand that we have designated stem cell factor (SCF). Recombinant or purified natural forms of the c-kit ligand induce proliferation of certain mast cell populations in vitro, and injection of recombinant SCF permits mast cells to develop in mast cell-deficient WCB6F1-S1/S1d mice. However, the effects of SCF on mast cell proliferation, maturation, and phenotype in normal mice in vivo were not investigated. We now report that local administration of SCF in vivo promotes the development of connective tissue-type mast cells (CTMC) in the skin of mice and that systemic administration of SCF induces the development of both CTMC and mucosal mast cells (MMC) in rats. Rats treated with SCF also develop significantly increased tissue levels of specific rat mast cell proteases (RMCP) characteristic of either CTMC (RMCP I) or MMC (RMCP II). These findings demonstrate that SCF can induce the expansion of both CTMC and MMC populations in vivo and show that SCF can regulate at least one cellular lineage that expresses c-kit, the mast cell, through complex effects on proliferation and maturation.

Animals↗

PubMed1991

Heterogeneity of murine bone marrow-derived mast cells: analysis of their proteinase content.

The expression of granule proteinases by murine bone marrow-derived mast cells (BMMC) grown in vitro was compared with that of serosal mast cells (SMC) from the peritoneal cavity. The granules in a proportion of BMMC (0.4-13%) and in all SMC were labelled with fluorescent antibodies against rat mast cell protease I (RMCP I). The granules of 1-47% of BMMC and 100% of SMC were labelled with antibodies against a 30,000 molecular weight (MW) murine intestinal mast cell proteinase (MIMCP). Four antigens from BMMC, ranging in MW from 28,000 to 32,000 and a single 28,000 antigen from SMC were detected on Western blot using anti-MIMCP antibodies. Only the 28,000 MW antigens from BMMC and SMC were visualized in blots probed with anti-RMCP I. BMMC grown in the presence of conditioned medium from activated splenocytes or from the WEHI-3B myelomonocytic cell line contained 52-118 ng and 3-25 ng MIMCP/10(6) cells respectively, whereas SMC lacked detectable MIMCP. The selective labelling of the 28,000 MW antigens in BMMC and SMC with anti-RMCP I and the variable expression of this antigen in BMMC as detected by immunofluorescence indicates that BMMC are not a homogeneous population of cells.

Animals↗

PubMed1990

Intestinal mucosal mast cells in Nippostrongylus-infected mice: lack of sensitivity to corticosteroids.

Immune reactions to enteric nematodes, in which mast cells are thought to play an important role, are abrogated following corticosteroid treatment of host animals. This is probably due, at least in part, to inhibition of cytokine production by T cells. It has proved difficult to block worm expulsion in mice with corticosteroids. We have therefore examined the effects of corticosteroids on mast cell numbers and concentrations of the mast cell granule-specific serine protease Mouse Intestinal Mast Cell Protease (MIMCP) in the intestines of mice infected with Nippostrongylus brasiliensis. Mucosal mast cell (MMC) numbers and concentrations of MIMCP were unaltered by steroid treatment. This is in marked contrast to Nippostrongylus-infected rats which showed decreases in both mast cell numbers and concentrations of the rat mucosal mast cell protease RMCP II after steroid treatment. This suggests that differentiated murine MMC are less dependent on T cells than those of the rat.

Animals↗

PubMed1990

Immune exclusion of Haemonchus contortus larvae in the sheep: effects on gastric mucin of immunization, larval challenge and treatment with dexamethasone.

The rapid expulsion of the gastric nematode Haemonchus contortus from primed sheep is a complex mechanism which probably involves immediate hypersensitivity reactions and mucus. Quantitative techniques were employed to determine the content and distribution of mucin in the gastric mucosae of sheep of varying immune status, following a single large challenge with H. contortus. Substantial depletion of both neutral and acidic mucin, following challenge, was noted in the gastric mucosae of naive sheep. When compared with normal controls, animals rendered immune by daily oral challenge had significant reductions in neutral mucin at the mucosal surface and increased quantities of acidic mucin deeper in the mucosa. Mucin distribution in immune sheep was not significantly altered 48 h after challenge. Treatment of immune animals with the corticosteroid dexamethasone, abrogated the protective response with gross depletion of mucus in challenged sheep, but had little measurable effect on the mucin profile of unchallenged animals, except for a slight increase in acidic mucin at the mucosal surface and the absence of any detectable mucin in the zone adjacent to the sub-mucosa. Immunity to H. contortus diminishes with time after immunization. Animals still immune 6 weeks after immunization were found to have mucin profiles which did not differ significantly from those of freshly immunized animals, whereas animals susceptible to re-infection 12 weeks after immunization had mucin profiles more closely resembling those seen in naive controls. Immunization by daily oral challenge was also accompanied by hyperplasia of the gastric mucosa which persisted for at least 12 weeks after immunization had ceased.

Animals↗