Intestinal infection with Trichinella spiralis induces distinct, regional immune responses

The aim of this study was to evaluate differences between the small and large intestines (SI and LI) with regard to colonization and immunity during infection with Trichinella spiralis. In orally infected C57BL/6 mice, the gender ratios of worms differed among the SI, cecum, and LI. Mucosal mastocytosis developed in the SI but not in the LI, consistent with reduced IL-9 and IL-13 production by explants from the LI. Despite these differences, worms were cleared at the same rate from both sites. Furthermore, IL-10 production was reduced in the LI, yet it was instrumental in limiting local inflammation. Finally, passive immunization of rat pups with tyvelose-specific antibodies effectively cleared fist-stage larvae from all intestinal regions. We conclude that despite regional differences in immune responsiveness and colonization, immune mechanisms that clear T. spiralis operate effectively throughout the intestinal tract.

The role of phosphoinositide-3-kinase in mast cell homing to the gastrointestinal tract

Phosphoinositide-3-kinases (PI3Ks) are a family of lipid kinases essential in a variety of physiological reactions. A series of gene-targeted mice lacking different PI3Ks and related molecules has enabled us to understand their in vivo roles, particularly those of class IA members. Studies on knockout mice lacking class IA PI3Ks and knock-in mice expressing mutant forms of enzymes have revealed the importance of this class of PI3Ks in mast cell development in the gastrointestinal tract. Here we studied the role of the p85a regulatory subunit, the most abundantly expressed regulatory subunit of class IA PI3Ks, using p85a knockout mice. Development of mast cells in the gastrointestinal tract but not in the skin was severely impaired in mice lacking the p85a regulatory subunit. Stem cell factor (SCF)-mediated signalling functions including proliferative response and chemotactic activities were both impaired in p85a knockout mast cells, likely due to the mast cell deficiency. Mastocytosis upon Strongyloides veneZuelensis infection was also impaired in p85alpha knockout mice. Reconstitution with Th2-conditioned but not untreated bone marrow-derived mast cells (BMMCs) restored anti-bacterial immunity, indicating the importance of Th2 response in addition to the recruitment of mast cells in the control of nematode infection.

IFN-gamma-independent effects of IL-12 during intestinal nematode infection

Expulsion of the gastrointestinal nematode Trichinella spiralis is associated with a pronounced mastocytosis mediated by a Th2-type response involving IL-4, IL-10, and IL-13. When exogenous rIL-12 was administered to T. spiralis-infected NIH mice, this resulted in significant suppression of intestinal mast cell responses, delayed worm expulsion, increased muscle larvae burdens, and a transient, but significant decrease in early Th2 cytokine secretion. rIL-12 treatment also altered chemokine expression in the jejunal mucosa. The effects of exogenous IL-12 administration were largely independent of IFN-gamma as shown by rIL-12 treatment of IFN-gamma knockout mice. Hence, IL-12 may play a significant biological role as a direct negative regulator of intestinal Th2 responses and may act to promote the survival of intestinal parasites in vivo also in the absence of IFN-gamma.

IgE Enhances Parasite Clearance and Regulates Mast Cell Responses in Mice Infected withTrichinella spiralis

Trichinella spiralis infection elicits a vigorous IgE response and pronounced intestinal and splenic mastocytosis in mice. Since IgE both activates mast cells (MC) and promotes their survival in culture, we examined its role in MC responses and parasite elimination in T. spiralis-infected mice. During primary infection, wild-type but not IgE-deficient (IgE(-/-)) BALB/c mice mounted a strong IgE response peaking 14 days into infection. The splenic mastocytosis observed in BALB/c mice following infection with T. spiralis was significantly diminished in IgE(-/-) mice while eosinophil responses were not diminished in either the blood or jejunum. Similar levels of peripheral blood eosinophilia and jejunal mastocytosis occurred in wild-type and IgE-deficient animals. Despite the normal MC response in the small intestine, serum levels of mouse MC protease-1 also were lower in parasite-infected IgE(-/-) animals and these animals were slower to eliminate the adult worms from the small intestine. The number of T. spiralis larvae present in the skeletal muscle of IgE(-/-) mice 28 days after primary infection was about twice that in BALB/c controls, and the fraction of larvae that was necrotic was reduced in the IgE-deficient animals. An intense deposition of IgE in and around the muscle larvae was observed in wild-type but not in IgE null mice. We conclude that IgE promotes parasite expulsion from the gut following T. spiralis infection and participates in the response to larval stages of the parasite. Furthermore, our observations support a role for IgE in the regulation of MC homeostasis in vivo.

Effects of anti-allergic drugs on intestinal mastocytosis and worm expulsion of rats infected with Neodiplostomum seoulense

The effects of anti-allergic drugs on intestinal mastocytosis and the expulsion of Neodiplostomum seoulense were observed in Sprague-Dawley rats, after oral infection with 500 metacercariae. The drugs used were hydroxyzine (a histamine receptor H1 blocker), cimetidine (a H2 blocker), cyclosporin-A (a helper T-cell suppressant), and prednisolone (a T- and B-cell suppressant). Infected, but untreated controls, and uninfected controls, were prepared. Worm recovery rate and intestinal mastocytosis were measured on weeks 1, 2, 3, 5, and 7 post-infection. Compared with the infected controls, worm expulsion was significantly (P < 0.05) delayed in hydroxyzine- and cimetidine-treated rats, despite mastocytosis being equally marked in the duodenum of all three groups. In the cyclosporin-A- and prednisolone-treated groups, mastocytosis was suppressed, but worm expulsion was only slightly delayed, without statistical significance. Our results suggest that binding of histamine to its receptors on intestinal smooth muscles is more important in terms of the expulsion of N. seoulense from rats than the levels of histamine alone, or mastocytosis.

IL-18 regulates intestinal mastocytosis and Th2 cytokine production independently of IFN-gamma during Trichinella spiralis infection

Expulsion of the gastrointestinal nematode Trichinella spiralis is associated with pronounced mastocytosis mediated by a Th2-type response involving IL-4, IL-10, and IL-13. Here we demonstrate that IL-18 is a key negative regulator of protective immune responses against T. spiralis in vivo. IL-18 knockout mice are highly resistant to T. spiralis infection, expel the worms rapidly and subsequently develop low levels of encysted muscle larvae. The increased speed of expulsion is correlated with high numbers of mucosal mast cells and an increase in IL-13 and IL-10 secretion. When normal mice were treated with rIL-18 in vivo, worm expulsion was notably delayed, and the development of mastocytosis and Th2 cytokine production was significantly reduced. The treatment had no effect on intestinal eosinophilia or goblet cell hyperplasia but specifically inhibited the development of mastocytosis. Addition of rIL-18 to in vitro cultures of bone marrow-derived mast cells resulted in a significant reduction in cell yields as well as in the number of IL-4-secreting mast cells. In vivo treatment of T. spiralis-infected IFN-gamma knockout mice with rIL-18 demonstrated that the inhibitory effect of IL-18 on mastocytosis and Th2 cytokine secretion is independent of IFN-gamma. Hence, IL-18 plays a significant biological role as a negative regulator of intestinal mast cell responses and may promote the survival of intestinal parasites in vivo.

Blockade of either alpha-4 or beta-7 integrins selectively inhibits intestinal mast cell hyperplasia and worm expulsion in response to Nippostrongylus brasiliensis infection

Mast cells are known to express high levels of alpha4 integrins including alpha4beta7 and are found in increased numbers in mucosal inflammation. Mast cell accumulation is particularly prominent in the intestine following nematode infection. The adhesion molecule requirements for this process have not yet been defined. The role of alpha4 and beta7 integrin chains in the intestinal mast cell hyperplasia following infection of rats with the nematode parasite Nippostrongylus brasiliensis was examined in this study. Rats were infected with N. brasiliensis larvae and treated with either anti-alpha4 (TA-2), anti-beta7 or isotype-matched control antibodies. The initial mast cell hyperplasia in response to N. brasiliensis infection was significantly inhibited by either anti-alpha4 or anti-beta7 treatment. In contrast, the intestinal eosinophil response to N. brasiliensis infection was not reduced at day 14 or day 16. Elevations in serum IgE levels due to N. brasiliensis infection were also not inhibited by anti-alpha4 or anti-beta7 antibody treatment. Anti-alpha4 antibody but not anti-beta7 antibody treatment also induced a small but significant decrease in the numbers of mast cells in tongue tissue. These data suggest a role for alpha4 integrins, in particular alpha4beta7, in the regulation of mast cell precursor migration to the intestine.

A role of mast cell glycosaminoglycans for the immunological expulsion of intestinal nematode, Strongyloides venezuelensis

We examined effects of mast cell glycosaminoglycans on the establishment of the intestinal nematode, Strongyloides venezuelensis, in the mouse small intestine. When intestinal mastocytosis occurred, surgically implanted adult worms could not invade and establish in the intestinal mucosa. In mast cell-deficient W/Wv mice, inhibition of adult worm invasion was not evident as compared with littermate +/+ control mice. Mucosal mastocytosis and inhibition of S. venezuelensis adult worm mucosal invasion was tightly correlated. To determine effector molecules for the invasion inhibition, adult worms were implanted with various sulfated carbohydrates including mast cell glycosaminoglycans. Among sulfated carbohydrates tested, chondroitin sulfate (ChS)-A, ChS-E, heparin, and dextran sulfate inhibited invasion of adult worms into intestinal mucosa in vivo. No significant inhibition was observed with ChS-C, desulfated chondroitin, and dextran. ChS-E, heparin, and dextran sulfate inhibited adhesion of S. venezuelensis adult worms to plastic surfaces in vitro. Furthermore, binding of intestinal epithelial cells to adhesion substances of S. venezuelensis, which have been implicated in mucosal invasion, was inhibited by ChS-E, heparin, and dextran sulfate. Because adult worms of S. venezuelensis were actively moving in the intestinal mucosa, probably exiting and reentering during infection, the possible expulsion mechanism for S. venezuelensis is inhibition by mast cell glycosaminoglycans of attachment and subsequent invasion of adult worms into intestinal epithelium.

Hymenolepis diminuta: praziquantel removal of adult tapeworms is followed by apoptotic down-regulation of mucosal mastocytosis

The rat tapeworm, Hymenolepis diminuta, induces mastocytosis, hypertrophy of enteric smooth muscle, alteration of enteric myoelectric activity, and slowed enteric transit of the rat host's intestine. This report examines the resolution of both tapeworm-induced mastocytosis and tissue changes during the period following removal of the tapeworm with Praziquantel (PZQ). The dynamics of the mucosal mast cell (MMC) population following removal of the tapeworms was assessed by histochemical identification of MMC and morphometric techniques. As a possible mechanism of MMC population regulation, MMC apoptosis was examined over the same experimental period using the in situ nick end labeling of fragmented DNA (TUNEL). Shifts in MMC numbers were correlated with functional and morphological changes of the intestine following removal of the adult-stage tapeworm. Ileal tissues from rats infected 32 days with H. diminuta (the beginning of plateau phase of tapeworm-induced chronic mastocytosis) were harvested 1, 2, 3, and 4 weeks after the PZQ treatment. Control ilea were obtained either from rats which were never infected and never treated with PZQ or from rats infected with H. diminuta for 32 days but not treated with PZQ. In order to detect MMC and apoptosis, tissue sections of ileum were doubled stained sequentially with Astra blue for MMC granules followed by a modification of the TUNEL technique. No alteration in MMC numbers were observed in PZQ-treated animals until 3 weeks after the removal of the tapeworms. The decline of MMC occurred in the mucosa and submucosa. MMC numbers first approached uninfected control levels at 4 weeks posttreatment. Coincident with the decline in mucosal MMC numbers, the rate of MMC entering apoptosis also declined. Simultaneously, ileal smooth muscle layers, hypertrophied by infection, and mucosal structures began the process of involution and atrophy. Apoptosis of MMC in the submucosa and muscularis mucosa was not detected. In conclusion, H. diminuta-elicited mastocytosis and increased thickness of both mucosa and muscularis externa do not begin a decline toward control values until 3 weeks after the parasites are gone and normal intestinal motility is restored. These data are consistent with the lack of MMC mediation of altered motility, and the decline in the rate of MMC apoptosis at 3 weeks post-PZQ suggests that apoptosis may play an important role in the involution of tapeworm-induced mastocytosis.

Cutaneous and gastrointestinal mastocytosis associated with cerebral toxoplasmosis

A patient with systemic cutaneous and gastrointestinal mastocytosis and associated meningoencephalitic toxoplasmosis is reported. The simultaneous occurrence of the two conditions and their regression after treatment of the toxoplasmosis suggest a possible relationship between the mast cell proliferation and the parasitic infection. Mast cell activation and stimulation may be transitory in response to a stimulus, causing reactional mastocytosis.

CD40-mediated stimulation contributes to lymphocyte proliferation, antibody production, eosinophilia, and mastocytosis during an in vivo type 2 response, but is not required for T cell IL-4 production

CD40/CD40 ligand interactions are required for the development of T cell-dependent Ab responses in vivo. The role of these cell surface molecules in contributing to T cell cytokine production and the development of effector populations other than B cells and T cells is, however, less well defined. We have examined the in vivo effects of blocking CD40/CD40 ligand interactions on the type 2 mucosal immune response that follows oral inoculation of mice with the nematode parasite, Heligmosomoides polygyrus. Administration of anti-gp39 (CD40L) mAb (MR1) blocked H. polygyrus-induced elevations in serum IgG1 levels and inhibited elevations in blood eosinophils and mucosal mast cells at day 14 after inoculation. Anti-gp39 mAb markedly inhibited B cell blastogenesis 8 days after H. polygyrus inoculation but did not inhibit elevations in B cell class II MHC expression. Maximal elevations in B7-2 expression required signaling through both CD40 and the IL-4R. Elevations in T cell cytokine gene expression and elevations in the number of IL-4-secreting cells were unaffected by treatment with anti-gp39 mAb, although IL-4 production was inhibited by anti-IL-4R mAb. These results suggest that CD40/CD40L interactions are not required to activate T cells to produce cytokines but are required for the activation and proliferation of other effector cells associated with the type 2 response.

cDNA sequencing of mouse alpha 1-microglobulin/inter-alpha-trypsin inhibitor light chain and its expression in acute inflammation

A cDNA encoding alpha 1-microglobulin (alpha 1mG)/inter-alpha-trypsin inhibitor light chain (ITI-LC) was cloned from mouse liver by reverse transcription-polymerase chain reaction and rapid amplification of cDNA ends. Sequence analysis of the cDNA showed that the basic molecular structure of the proprotein was similar to that in other animals, so that two mature proteins, alpha 1mG and ITI-LC, could be produced from the proprotein translated from the mRNA. Since ITI-LC is known as a positive acute phase reactant and since ITI-LC is genetically identical with mast cell proteinase inhibitor, trypstatin, we examined the mRNA level in the liver of parasite-infected mice showing extensive mastocytosis. The mRNA level was, however, not significantly changed during inflammatory processes, except for a slight increase on day 8 post-infection.

Expulsion of Hymenolepis nana from mice with congenital deficiencies of IgE production or of mast cell development

The roles of IgE and mast cells on expulsion of adult Hymenolepis nana from the intestine were examined in mice. IgE-dependency was determined by comparing congenitally IgE-deficient SJA/9 and IgE-producing SJL/J mice infected with 50 H. nana eggs. Anti-H. nana IgE antibody was detected at three weeks post infection (p.i.) in SJL but not in SJA mice. The number of adult worms in the intestines of SJA and of SJL mice were similar at two weeks, but significantly more were found in SJA mice at three weeks p.i. Treatment of mice with anti-epsilon antibody also resulted in an increased worm burden at three weeks, suggesting participation of IgE in expulsion of H. nana. Intestinal mastocytosis was induced by infection regardless of the IgE status of the mice. Mast cell-dependency was tested in mast cell-deficient W/Wv and in normal littermate +/+ mice infected with 100 H. nana eggs. Anti-H. nana antibody was detected in both groups of mice at three weeks p.i. Worm expulsion seemed to be mast cell dependent because expulsion was less complete in W/Wv mice at three weeks p.i. Peripheral blood eosinophilia was comparable at three weeks p.i. in both IgE and mast cell sufficient and deficient mice. These results suggest that IgE and mast cells participate in the expulsion of H. nana adults from intestine in mice.

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.

Mucosal mast cells and the expulsive mechanisms of mice against Strongyloides venezuelensis

The possible importance of mucosal mast cells in the expulsive mechanisms of mice against Strongyloides venezuelensis was examined. After a primary infection by subcutaneous inoculation with various doses into C57BL/6 mice, about 50% of the initial dose of infective larvae (L3) became adult worms and, regardless of the dose of infection, they were completely expelled by Day 12 with similar kinetics. Intestinal mastocytosis at the time of expulsion was comparable among groups given different doses of infection. A kinetic study after infection with 2000 L3 in C57BL/6 mice revealed that mastocytosis started from Day 8, rapidly reached a peak on Day 12, and then gradually decreased. The strongest mastocytosis was observed in the upper one sixth of the small intestine where the majority of adult worms parasitized. Over 80% of mast cells induced by the infection were located in the intestinal epithelial layer. When mast cell-deficient W/Wv and their normal littermate +/+ mice were infected with 1000 L3, expulsion was significantly delayed in W/Wv mice, though adult worms were eventually expelled by Day 18 in W/Wv mice. Delayed expulsion as well as defective mast cell responses of W/Wv mice were completely restored by bone marrow grafting 10 weeks prior to infection. These results show that, like S. ratti infection, intestinal mucosal mast cells are important in causing expulsion of S. venezuelensis.

Influence of variation in host strain and parasite isolate on inflammatory and antibody responses to Trichinella spiralis in mice

Variation in the immunogenicity of 3 isolates of Trichinella spiralis was assessed by the parameters of adult worm recovery, mast cell, eosinophil and antibody responses in mice of defined response phenotype. The levels of the protective, inflammatory and immune responses induced by infection differed between the isolates. Isolates showed considerable variation in the capacity to elicit mast cell and eosinophil responses. All induced increases in parasite-specific antibody, levels of total (IgGAM) antibody and of IgM and IgG isotypes rose steadily after infection, but there were significant differences in levels of response. The IgGAM response was correlated with the number of worms present, i.e. the greatest response was seen in low responder (C57BL/10) mice infected with the longest-surviving isolates. All isolates elicited specific IgG1 and IgG2a antibodies after infection, although, again, there were isolate-specific differences in the levels and kinetics of response. Levels of these isotypes were always higher, although not significantly so, in high-responder NIH mice. Low-responder mice showed higher IgE serum levels than high-responder mice after infection, one isolate giving much higher IgE values than the other two.

The in vivo role of stem cell factor (c-kit ligand) on mastocytosis and host protective immunity to the intestinal nematode Trichinella spiralis in mice

The role of stem cell factor (SCF) in the generation of intestinal mast cell hyperplasia and host protective immunity following helminth infection was investigated using the Trichinella spiralis/mouse model. In vivo administration of a monoclonal antibody specific for the receptor for SCF (c-kit) was found to completely prevent the generation of intestinal mastocytosis normally observed following T. spiralis infection. This was reflected by markedly reduced intestinal mast cell protease (IMCP) levels in both tissue and serum. Moreover, animals treated with anti-c-kit antibody failed to show any evidence of worm expulsion from the gut. The data demonstrate for the first time, a critical role for the SCF in the generation of mucosal mastocytosis and host protective immunity following an intestinal helminth infection.