Protection against Nippostrongylus brasiliensis by adoptive immunization with immune thoracic duct lymphocytes

Innate immune response mechanisms in the intestinal epithelium: potential roles for mast cells and goblet cells in the expulsion of adult Trichinella spiralis

SUMMARYGastrointestinal infection with the nematode Trichinella spiralis is accompanied by a rapid and reversible expansion of the mucosal mast cell and goblet cell populations in the intestinal epithelium, which is associated with the release of their mediators into the gut lumen. Both goblet cell and mast cell hyperplasia are highly dependent on mucosal T-cells and augmented by the cytokines IL-4 and IL-13. However, the contribution of both mast and goblet cells, and the mediators they produce, to the expulsion of the adults of T. spiralis is only beginning to be elucidated through studies predominantly employing T. spiralis-mouse models. In the present article, we review the factors proposed to control T. spiralis-induced mucosal mast cell (MMC) and goblet cell differentiation in the small intestine, and focus on some key MMC and goblet cell effector molecules which may contribute to the expulsion of adult worms and/or inhibition of larval development.

Chemokine and cytokine expression in murine intestinal epithelium following Nippostrongylus brasiliensis infection

Infection of mice with the nematode parasite Nippostrongylus brasiliensis results in a well characterized intestinal mastocytosis with intraepithelial migration of mucosal mast cells (MMC). The molecules mediating this response are unknown. We examined expression of several putative mast cell chemoattractants in intestinal epithelium following N. brasiliensis infection. Expression of the chemokines monocyte chemoattractant protein-1 (MCP-1), macrophage inflammatory protein-1 alpha (MIP-1alpha), RANTES (regulated on activation normal T-cell expressed and secreted), fractalkine, and thymocyte expressed chemokine (TECK); and the cytokines stem cell factor (SCF) and transforming growth factor beta1 (TGFbeta1), was constitutive and no alteration was detected following infection. MCP-1 expression was also constitutive but at much lower levels and increased expression was detected on days 7 and 14 postinfection. Expression of MCP-1 in whole jejunum was at much higher levels than in epithelium. Constitutive expression of MCP-1, MIP-1alpha and TGFbeta1 was also detected in cultured bone marrow-derived homologues of MMC. In an intestinal epithelial cell line (CMT-93), there was constitutive expression of SCF, TGFalpha1, fractalkine and MCP-1. The results show that, in vivo, epithelium is a potentially important source of mast cell chemoattractants.

Helicobacter pylori vaccines and mechanisms of effective immunity: is mucus the key?

In this theoretical article, the hypothesis is proposed that immunization against gastric helicobacter infection is mediated by CD4+ T-cell induced changes in mucus production. Vaccine development for the gastric pathogen Helicobacter pylori has encountered several problems. Resolving these problems is impeded by our lack of understanding of the mechanisms by which the immune response influences bacterial colonization. Protective immunity requires CD4+ T cells, but the majority of helicobacters are located in the mucus of the gastric lumen, away from the epithelial surface. Evidence suggests that this mechanism functions independently of antibodies, so how this is achieved is unknown. Clues to this mechanism may be provided by immune clearance of nematode infection. Similar to H. pylori, expulsion of the intestinal nematode, Nippostrongylus brasiliensis, in rodents is mediated by CD4+ T-cell changes in the numbers of goblet cells and the type of mucins secreted into the gut. Immune-mediated changes in secretion of gastric mucins could similarly be responsible for the reductions in helicobacter colonization seen in immunized animals. Helicobacter pylori are highly motile bacteria that have evolved to inhabit their specialized niche. Alterations in their mucus environment could influence their motility, such that the bacteria cannot remain efficiently within the mucus and are flushed away.

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.

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.

Cytofluorometric quantification of IgE and IgE receptors on individual mast cells

Information about the IgE receptor and IgE content of mast cells under different conditions in vivo is essential for further understanding the functions of the mast cell-IgE system. A cytofluorometric method for measuring cell-bound IgE on individual mast cells was therefore explored using peritoneal mast cells of Sprague-Dawley rats infected with the nematode N. brasiliensis and rat basophilic leukaemia cells (RBL-1) as experimental models. We systematically studied the effects of variables such as fixation, incubation time, temperature and concentrations of antibody on the fluorescence emission of the mast cells. Optimum conditions were selected for the quantitative measurement of IgE at the single-cell level using direct labelling with FITC-conjugated goat anti-rat IgE(Fc). Polystyrene beads with a defined fluorophor content and a fluorescent uranyl glass were used to standardise the measurement procedure. A linear relationship between fluorescence intensity and IgE concentration was obtained by fluorescence measurements on RBL-1 cells incubated in rat IgE. In the case of rat peritoneal mast cells it was possible to saturate the IgE receptors by incubating the mast cells in rat IgE. By measuring the mast cells before and after IgE incubation, the relative content of IgE, the relative number of IgE receptors and the degree of receptor saturation could be estimated. In this way we measured the IgE content of peritoneal mast cells of Sprague-Dawley rats maintained under pathogen-free conditions. The distribution of IgE content in the mast-cell populations was extremely variable. Up to 30% of the mast cells in individual populations contained little or no IgE, but very few if any of the cells lacked IgE receptors. On average, 60-70% of the receptors available for binding were occupied by IgE in these normal rats.

Application of an immunocolloid gold technique for the ultrastructural demonstration of IgE-receptor complexes on rat mast cells

In previous works using cytofluorometry, we demonstrated a broad range of IgE and IgE-receptor levels within individual mast cell populations with a 60 to 80% occupancy of the IgE receptors on mast cells by native IgE. This study was performed in order to confirm our previous findings using an independent method and to visualize the distribution of IgE-receptor complexes on mast cells at an ultrastructural level. For this purpose an indirect immunocolloidal gold-labelling technique has been applied. By counting the number of labelled gold particles, a relative measure of IgE-receptor surface expression and IgE occupancy of the receptors could be obtained. With respect to mast cell morphology and anti-IgE binding specificity criteria, 1% glutaraldehyde + 4% paraformaldehyde (1:1, vol/vol) was found to be the best of the seven fixatives applied in this study. This technique revealed numerous gold particles on the surface of mast cells from barrier-maintained rats (26 +/- 11 per mast cell section, mean +/- SD). Increased numbers of gold particles were counted if the mast cells were incubated with rat myeloma IgE (20 micrograms/ml) (46 +/- 33 per mast cell section, mean +/- SD). There were significantly increased numbers of gold particles on the mast cells of rats infected with N. brasiliensis (126 +/- 30 per mast cell section, mean +/- SD). This indicates that some of the IgE receptors (about 50% of the total number of IgE receptors in this case) on mast cells were occupied by native IgE and that parasite infection significantly increased the number of IgE molecules on the surface of the mast cells. These results correspond with the findings we have made using the cytofluorometric technique and confirm the large individual variations in the density of IgE receptors and IgE among the mast cells of a given cell population. Macrophages, lymphocytes and eosinophils, carrying the low-affinity IgE receptors (Fc epsilon RII), contained less than 5 (normal rats after incubation in rat IgE) or 10 (nematode-infected rats) gold particles per cell section. We also observed some non-granulated lymphocyte-like cells which bound a large number of gold particles after incubation with rat myeloma IgE (20 micrograms/ml), indicating that they contained IgE receptors Fc epsilon RI). They were interpreted as mast cell precursors which have previously been shown to exist in the peritoneal cavity.

Reconstitution by bone marrow grafting of the defective protective capacity at the migratory phase but not at the intestinal phase of Nippostrongylus brasiliensis infection in W/Wv mice

After a primary infection by subcutaneous inoculation with the infective larvae (L3) of Nippostrongylus brasiliensis, the intestinal worm burden was higher and expulsion was slower in W/Wv mice than in +/+ mice. When the course of infection was segregated into the migratory and intestinal phases, protection during the migratory phase examined by the larval recovery from the lungs and that during the intestinal phase measured by worm burden after intraduodenal implantation with adult worms were both defective in W/Wv mice. The higher susceptibility of W/Wv mice during the migratory phase was normalized by bone marrow reconstitution. On the other hand, higher susceptibility of W/Wv mice during the intestinal phase, which was measured by worm burden 24 h after intraduodenal implantation of the larvae recovered from the lungs of rats, was not normalized by bone marrow grafting. Furthermore, slower expulsion seen in W/Wv mice after intraduodenal implantation with adult worms was not hastened by bone marrow reconstitution. These results indicate that the protective mechanisms against N. brasiliensis operating during the migratory phase and those during the intestinal phase were different in terms of bone marrow dependency and that non-myeloid cells utilizing c-kit ligand/receptor system to express their functions are involved in the mucosal defence against N. brasiliensis.

Dose-response studies of depletion and repopulation of rat intestinal mucosal mast cells after irradiation

The effects of radiation on gut mucosal mast cells (MMC) and tissue eosinophils were examined. Groups of rat were given single doses of whole-body irradiation from 0.5 to 5 Gy. Serum rat mast cell protease II (RMCPII) concentration showed a significant dose-dependent fall after 1 Gy on day 3 and 1.5 Gy on day 7. MMC counts and tissue RMCPII values on day 7 decreased significantly by 70% after 1 Gy and were undetectable with larger doses. Rat with normal and expanded MMC populations were irradiated or given anaphylaxis. Serum RMCPII concentrations did not change after irradiation, but there was a 10-fold increase in RMCPII after anaphylaxis. Tissue eosinophils in jejunum were 50% of control at 7 days after 2 Gy, and this effect was progressively more marked with higher doses. Similar effects on MMC and eosinophils were demonstrated in ileum, ascending colon and rectum. After 4.5 Gy, repopulation of the gut with MMC did not occur until week 3-4 postirradiation and MMC counts were still 50% below those of controls at 5 weeks postirradiation. Counts of tissue eosinophils 5 weeks after 4.5 Gy irradiation had returned to control levels in jejunum but were still significantly depleted in colon. These experiments show that the high radiosensitivity of rat intestinal MMC is dose dependent, similar at four different levels in the gastrointestinal tract and does not lead to immediate release of granule protease; repopulation with MMC does not begin until at 3 weeks postirradiation.

Altered expression of mast cell proteases in the rat. Quantitative and immunohistochemical analysis of the distribution of rat mast cell proteases I and II during helminth infection

Expression of mast cell granule protease is regulated in a tissue-specific fashion in the rat. The granule chymases rat mast cell proteases I and II (RMCP I and II) predominate in non-mucosal and mucosal sites, respectively. Intestinal mastocytosis, a T cell-mediated phenomenon associated with enteric nematodiasis, is accompanied by massive local expression of RMCP II and by release of this protease systemically into blood. The present observations, where both RMCP I and II have been quantified by ELISA and immunolocalized by paired fluorescence, show that the expression of both proteases in parasitized rats is profoundly altered at sites distant from infection. Thus, RMCP II-containing cells are recruited to liver and thymus, and in the thymus there is a > 2-fold increase in concentration of RMCP I. The latter protease is depleted from bone marrow and mesenteric lymph node early during infection, but concentrations of RMCP I in trachea/larynx, lung, and skeletal and cardiac muscle are increased. Increased mast cell counts in intestine, lung and liver are highly correlated with tissue concentrations of RMCP II.

Persistent infection of Strongyloides venezuelensis and normal expulsion of Nippostrongylus brasiliensis in Mongolian gerbils, Meriones unguiculatus, with reference to the cellular responses in the intestinal mucosa

The kinetics of daily faecal egg count, worm burdens, and intestinal cellular responses were examined in Mongolian gerbils after infection with either Strongyloides venezuelensis or Nippostrongylus brasiliensis alone, or concurrently with both parasites. The results show that, both in individual and concurrent infections, S. venezuelensis infection persisted for over 10 weeks and elicited a gradual increase in number of mast cells in the jejunal mucosa. On the other hand, N. brasiliensis worms were expelled by 3 weeks in association with goblet cell hyperplasia. These results suggest that effector/regulator cells involved in worm expulsion are different and highly selective depending on the genus of intestinal helminths.

Changes in distribution of Ia antigen on epithelium of the jejunum and ileum in rats infected with Nippostrongylus brasiliensis

This study compared the tissue distribution and cellular expression of Ia antigen in jejunal and ileal epithelium at various stages of intestinal inflammation produced by infecting rats with the nematode parasite Nippostrongylus brasiliensis. Tissues were examined at Day 0 (control), Day 4 (early), Day 10 (acute), and Day 16 (recovering). Frozen sections were stained with the MRC OX-4 anti-Ia monoclonal antibody using an immunoperoxidase technique. Control jejunal sections demonstrated positive epithelial Ia expression mainly in the mid-regions of the villi. The stain appeared to be mostly intracellular in the supranuclear area; the basolateral membrane stained faintly. At Day 4, a greater percentage of the epithelial cells expressed Ia, including those at the tips of the villi. The Day 10 sections demonstrated no staining at all of villus enterocytes, but the crypt epithelium was Ia positive. At Day 16, the pattern of Ia expression was similar to that seen in the early infection. In the ileum, stain was present in enterocytes over most of the villus and crypt regions except in the villus-crypt junction and did not change significantly during infection. We conclude that the changes in the expression of Ia antigen by intestinal epithelium are local to the site of infection and probably occur as a consequence of the host's inflammatory response.

Ion transport abnormalities in inflamed rat jejunum. Involvement of mast cells and nerves

Basal and stimulated changes in ion transport in vitro were examined in jejunal mucosa from rats during inflammation produced after infection with the nematode Nippostrongylus brasiliensis. The gut was acutely inflamed at days 7 and 10 when net secretion of Na+ and Cl- ions was evident. Serum levels of rat mast cell protease II were elevated, providing evidence for mast cell activation. In addition, the magnitude of the short-circuit current responses to electrical transmural stimulation of enteric nerves (but not to histamine in the presence of neural blockade) were significantly reduced (p less than 0.01) to 17%-33% of control values, suggesting abnormalities of mucosal nerves. Following worm expulsion, serum levels of rat mast cell protease II and ion transport returned to normal. However, mastocytosis was apparent in gut mucosa and parasite antigen stimulated net secretion. In the absence of antigen, short-circuit current responses to nerve stimulation were increased (to 122% of controls; p less than 0.05). These findings suggest that changes in mast cells and enteric nerves occur during inflammation in this model and implicate neural and mast cell interactions with the epithelium in producing the ion-transport abnormalities.

Intestinal mucosal injury is associated with mast cell activation and leukotriene generation during Nippostrongylus-induced inflammation in the rat

We examined mucosal injury in the jejunum of the rat during infection with the nematode parasite, Nippostrongylus brasiliensis (Nb). Injury was documented morphologically (increase in crypt length with or without villus atrophy) and biochemically (activities of digestive or proliferative enzymes) and related to mast cell activation and leukotriene generation. At day 4 crypt length and thymidine kinase activity were increased; no changes in villus parameters were recorded. No evidence of mast cell activation was found and leukotriene levels in the mucosa were normal. At day 7, the gut was acutely inflamed and edema was present at the tips of the villi. This progressed to enterocyte detachment, resulting in villus atrophy with decreased activities of brush border enzymes. At this stage mucosal histamine was decreased and rat mast cell protease II (RMCP II) was increased in serum, indicating mast cell activation. In addition, mucosal leukotrienes (LTB4, LTC4, LTE4) were present in significant quantities. Following worm expulsion, the villus abnormalities resolved and serum RMCP II returned to normal. However, the crypt hyperplasia persisted. Our results suggest that during Nb infection at least two components of injury can be identified. One component, epithelial injury at the villus tips, may be related to activation of mucosal mast cells.

Strongyloides ratti: formation of protection in rats by excretory/secretory products of adult worms

Formation of a marked protective immunity against the challenge infection was found in the rats immunized with excretory/secretory (ES) products of Strongyloides ratti adult worms. Immunization by intraduodenal injection of ES products reduced both the fecal egg counts and the adult worm burden by subcutaneous inoculation of infective larvae and by an intraduodenal implantation. The duration of parasitism in the immunized rats, however, was not shortened compared with that of control rats. The normal migration of subcutaneously challenged larvae was not affected by ES product immunization. Intestinal mastocytosis occurred according to the appearance of adult worms in the small intestine of the immunized rats earlier than it did in controls. This result suggests that mastocytosis is involved in the induction of protection by ES products of S. ratti adult worms.

Gut mucosal mast cells in Nippostrongylus-primed rats are the major source of secreted rat mast cell protease II following systemic anaphylaxis

The distribution of the predominant chymotrypsin-like enzyme of mucosal mast cells (rat mast cell protease II: RMCP II) was examined in naive and Nippostrongylus-primed rats both before and after the induction of systemic anaphylaxis. Anaphylactic secretion of RMCP II following i.v. challenge of primed rats with worm antigen was accompanied by significant depletion of this enzyme from the jejunal and gastric mucosae; the concentrations were not altered in the ileum and colon. Despite significant increases in the levels of RMCP II in lung and mesenteric lymph node following infection with N. brasiliensis there was no anaphylactic depletion of this enzyme from these sites. No RMCP II was detected in liver, spleen, kidney or bone marrow either before or after systemic anaphylaxis. Mucosal mast cells were depleted from the jejunal, gastric and colonic mucosae following antigen challenge of primed rats. These data provide further evidence that gastrointestinal mucosal mast cells are the major source of secreted RMCP II following systemic anaphylaxis in the rat.

Glycosaminoglycans in rat mucosal mast cells

Rats were infected with the nematode Nippostrongylus brasiliensis, resulting in an approx. 5-fold increase in the number of mucosal mast cells and the histamine content of the intestinal (jejunum) wall. After injection of the infected animals with inorganic [35S]sulphate, a similar increase in the yield of labelled intestinal glycosaminoglycans was observed, compared with uninfected control rats. Autoradiography showed a highly selective labelling of the numerous mucosal mast cells and of the few connective-tissue mast cells in the subserosal region of the bowel. Analysis of the labelled polysaccharide from the infected animals showed that almost 60% of this material consisted of oversulphated galactosaminoglycan, whereas heparin-related polysaccharides accounted for only 13%. The galactosaminoglycan contained 4-monosulphated and 4,6-disulphated N-acetylgalactosamine residues in approx. 5:1 molar ratio, both being linked to D-glucuronic acid residues; the occurrence of L-iduronic acid units could not be excluded. No significant difference in structure was found between this polysaccharide and the corresponding component isolated from uninfected rats. It is concluded that the major polysaccharide produced by rat mucosal mast cells in vivo is an oversulphated galactosaminoglycan rather than heparin.

Depletion of mucosal mast cell protease by corticosteroids: effect on intestinal anaphylaxis in the rat

Rats primed by infection with the intestinal nematode Nippostrongylus brasiliensis and challenged intravenously with soluble whole-worm antigen undergo systemic anaphylactic shock. The primary lesions are in the gut and include increased permeability of the mucosa together with release, into enteric secretions, of a mucosal mast cell (MMC)-specific serine proteinase, rat mast cell protease II (RMCP-II). This enzyme is also released into the blood of shocked rats. These manifestations of anaphylaxis were abolished in rats previously treated with corticosteroids (methylprednisolone acetate, 25 mg per kg of body weight, 48 and 24 hr before i.v. challenge with antigen). Suppression of the response was associated with depletion of RMCP-II and of MMC from the intestinal mucosa. Depletion occurred 4-24 hr after treatment with as little as 1 mg of methylprednisolone per kg. By contrast, neither connective tissue mast cells nor serum levels of parasite-specific IgE were depleted in rats given 2 X 25 mg of methylprednisolone per kg. The capacity of unprimed treated rats to mount passive cutaneous anaphylaxis was, however, impaired.

Mucosal mast cells are functionally active during spontaneous expulsion of intestinal nematode infections in rat

Infestation of the gastrointestinal tract by parasitic nematodes is invariably associated with mucosal mastocytosis, which is a thymus-dependent phenomenon in parasitized rats, and is adoptively transferable with a T cell-enriched population of thoracic duct lymphocytes. When derived by in vitro culture, mucosal mast cells (MMC) arise from a bone marrow precursor after stimulation by T cell-derived factors. In rats infected with the nematode Trichinella spiralis, mucosal mastocytosis is temporally associated with the immune expulsion of the adult worms whereas in the case of Nippostrongylus brasiliensis, mastocytosis is frequently observed to occur after worm expulsion has been completed. Consequently, there has been doubt as to whether MMC are active and serve a functional role in the expulsion of rat intestinal nematodes. MMC contain and secrete a neutral proteinase, rat mast cell protease II (RMCP II); detection and assay of secreted RMCP II therefore provides a direct measurement of MMC activity. Here we describe the release of this enzyme into the blood of rats infected with N. brasiliensis or T. spiralis. Our results show that the systemic secretion of RMCP II coincides with the immune expulsion of these nematodes, demonstrating clearly for the first time that rat MMC are functionally active during the immune elimination of primary nematode infections.

Concomitant detection of mucosal mast cells and eosinophils in the intestines of normal and Nippostrongylus-immune rats. A re-evaluation of histochemical and immunocytochemical techniques

The granules of mucosal mast cells (MMC) in the rat and man are apparently poorly fixed with formaldehyde and special fixation techniques are normally used to demonstrate MMC glycosaminoglycans (GAG) in these two species. However such techniques do not permit the study of MMC granule enzyme cytochemistry or the demonstration of eosinophils. We have, therefore, examined some histochemical and immunocytochemical properties of MMC and eosinophils in normal and parasitised rats following various fixation procedures. Immersion fixation of rat intestine in 4% paraformaldehyde for 6 h not only facilitated the demonstration of MMC glycosaminoglycans with basic dyes but also permitted the concomitant staining of eosinophils with acidophilic dyes. A MMC granule-associated serine esterase was also demonstrated by enzyme cytochemistry and rat mast cell protease II was detected within MMC granules by immunocytochemistry. This new methodology obviates the requirement for separate fixation procedures in the identification and characterisation of MMC/eosinophil interactions in normal and parasitised rat intestinal mucosa.

Strongyloides ratti: the role of enteral antigenic stimuli by adult worms in the generation of protective immunity in rats

Immunogenicity of adult Strongyloides ratti was studied in rats. Immunization of rats by intraduodenal implantation of adult worms could completely inhibit the egg production and hasten the expulsion of challenged worms which were developed from subcutaneously inoculated L3 or were implanted intraduodenally as adults. Enteral immunization by intraduodenal implantation of adult worms was, however, not able to affect the esophageal larval output of the challenge infection with L3. In contrast to enteral immunization with adult worms, immunization by full sequence of a primary infection or by a combination of drug-abbreviated infection and adult worm implantation could suppress the esophageal larval output of the challenge infection. The relationship between the host defense mechanism and the life cycle of S. ratti is discussed.

Amines of the mucosal mast cell of the gut in normal and nematode infected rats

Infection with the nematode N. brasiliensis is accompanied by a marked increase of the number of mucosal mast cells (MMC) and the mucosal content of histamine and 5-hydroxytryptamine (5-HT). We compared amine levels, determined by ion exchange and high performance liquid chromatography (HPLC) with numbers of MMC and enterochromaffin cells (ECC). Furthermore, we measured 5-HT cytofluorometrically in individual MMC and ECC. The cellular distribution of 5-HT was studied immunohistochemically. Our results corroborate previous findings that histamine is stored in MMC. Quotients between histamine content and numbers of MMC decreased throughout the period of worm expulsion, followed by a recovery, suggesting a histamine release during this defense reaction. The HPLC analysis gave no evidence for a storage of dopamine in MMC. ECC and MMC of normal and infected rats showed a formaldehyde induced fluorescence and 5-HT immunoreactivity. The formaldehyde induced fluorescence of MMC from normal rats was about 10% that of ECC, but MMC exceeded ECC three times by numbers. These findings suggest that a considerable proportion of the intestinal 5-HT in the normal rat is stored in MMC. ECC numbers did not change during the infection and their content of 5-HT was unchanged, as judged by cytofluorometry. The cytofluorometric measurements showed that the intensity of the monoamine fluorescence from the MMC of infected animals was about three times as high as that of controls. It was concluded that the increased tissue levels of 5-HT was due to both an increase in MMC numbers and an increase in the 5-HT content of individual MMC. The results suggest a different role for histamine and 5-HT in the defense reaction towards the nematode infection.

Immunity to Strongyloides ratti in rats. 1. Adoptive transfer with mesenteric lymph node cells

Adoptive transfer of immunity against the enteral phase of Strongyloides ratti was monitored using four parameters; namely, number of worms recovered, position occupied in the host's small intestine, worm length and fecundity. When immune mesenteric lymph node cells (IMLNC) were transferred from donors infected for 20, 26 or 32 days into recipients infected for 3 days, a marked acceleration of worm expulsion was evident by day 16 post-infection (p.i.). IMLNC from day-16 p.i. donors did not transfer expulsion. In an experiment in which recipients were given 2 x 10(8) or 1 x 10(8) IMLNC from donors infected for 26 days, accelerated worm expulsion occurred only with the higher inoculum, although manifestations of direct worm immunity, i.e. altered position and reduced length and fecundity, were evident in both cases. Transfer of IMLNC appeared to have no effect upon worm establishment; when cells were transferred on the day of infection a period of 16 days was necessary to effect both direct anti-worm immunity and expulsion, although the former was evident on day 14 p.i. However, when IMLNC were transferred to rats already infected for 6 days, a very significant reduction of their worm burden was apparent 10 days after IMLNC transfer.