Interleukin 25 regulates type 2 cytokine-dependent immunity and limits chronic inflammation in the gastrointestinal tract.

The cytokine interleukin (IL) 25 has been implicated in the initiation of type 2 immunity by driving the expression of type 2 cytokines such as IL-5 and IL-13, although its role in the regulation of immunity and infection-induced inflammation is unknown. Here, we identify a dual function for IL-25: first, in promoting type 2 cytokine-dependent immunity to gastrointestinal helminth infection and, second, in limiting proinflammatory cytokine production and chronic intestinal inflammation. Treatment of genetically susceptible mice with exogenous IL-25 promoted type 2 cytokine responses and immunity to Trichuris. IL-25 was constitutively expressed by CD4+ and CD8+ T cells in the gut of mouse strains that are resistant to Trichuris, and IL-25-deficient mice on a genetically resistant background failed to develop a type 2 immune response or eradicate infection. Furthermore, chronically infected IL-25(-/-) mice developed severe infection-induced intestinal inflammation associated with heightened expression of interferon-gamma and IL-17, identifying a role for IL-25 in limiting pathologic inflammation at mucosal sites. Therefore, IL-25 is not only a critical mediator of type 2 immunity, but is also required for the regulation of inflammation in the gastrointestinal tract.

Leukotriene B4, an activation product of mast cells, is a chemoattractant for their progenitors.

Mast cells are tissue-resident cells with important functions in allergy and inflammation. Pluripotential hematopoietic stem cells in the bone marrow give rise to committed mast cell progenitors that transit via the blood to tissues throughout the body, where they mature. Knowledge is limited about the factors that release mast cell progenitors from the bone marrow or recruit them to remote tissues. Mouse femoral bone marrow cells were cultured with IL-3 for 2 wk and a range of chemotactic agents were tested on the c-kit(+) population. Cells were remarkably refractory and no chemotaxis was induced by any chemokines tested. However, supernatants from activated mature mast cells induced pronounced chemotaxis, with the active principle identified as leukotriene (LT) B(4). Other activation products were inactive. LTB(4) was highly chemotactic for 2-wk-old cells, but not mature cells, correlating with a loss of mRNA for the LTB(4) receptor, BLT1. Immature cells also accumulated in vivo in response to intradermally injected LTB(4). Furthermore, LTB(4) was highly potent in attracting mast cell progenitors from freshly isolated bone marrow cell suspensions. Finally, LTB(4) was a potent chemoattractant for human cord blood-derived immature, but not mature, mast cells. These results suggest an autocrine role for LTB(4) in regulating tissue mast cell numbers.

Novel gene expression responses in the ovine abomasal mucosa to infection with the gastric nematode Teladorsagia circumcincta.

Infection of sheep with the gastric nematode Teladorsagia circumcincta results in distinct Th2-type changes in the mucosa, including mucous neck cell and mast cell hyperplasia, eosinophilia, recruitment of IgA/IgE producing cells and neutrophils, altered T-cell subsets and mucosal hypertrophy. To address the protective mechanisms generated in animals on previous exposure to this parasite, gene expression profiling was carried out using samples of abomasal mucosa collected pre- and post- challenge from animals of differing immune status, using an experimental model of T. circumcincta infection. Recently developed ovine cDNA arrays were used to compare the abomasal responses of sheep immunised by trickle infection with worm-naïve sheep, following a single oral challenge of 50 000 T. circumcincta L3. Key changes were validated using qRT-PCR techniques. Immune animals demonstrated highly significant increases in levels of transcripts normally associated with cytotoxicity such as granulysin and granzymes A, B and H, as well as mucous-cell derived transcripts, predominantly calcium-activated chloride channel 1 (CLCA1). Challenge infection also induced up-regulation of transcripts potentially involved in initiating or modulating the immune response, such as heat shock proteins, complement factors and the chemokine CCL2. In contrast, there was marked infection-associated down-regulation of gene expression of members of the gastric lysozyme family. The changes in gene expression levels described here may reflect roles in direct anti-parasitic effects, immuno-modulation or tissue repair.

Extended cleavage specificity of mMCP-1, the major mucosal mast cell protease in mouse-high specificity indicates high substrate selectivity.

Mucosal mast cells are in the mouse predominantly found in the epithelium of the gastrointestinal tract. They express the beta-chymases mMCP-1 and mMCP-2. During nematode infections these intraepithelial mast cells increase in numbers and high amounts of mMCP-1 appear in the jejunal lumen and in the circulation. A targeted deletion of this enzyme leads to decreased ability to expel the intraepithelial nematode Trichinella spiralis. A suggested role for mMCP-1 is alteration of epithelial permeability by direct or indirect degradation of epithelial and endothelial targets, however, no such substrates have yet been identified. To enable a screening for natural substrates we performed a detailed analysis of the extended cleavage specificity of mMCP-1, using substrate phage display technology. In positions P1 and P1' distinct preferences for Phe and Ser, respectively, were observed. In position P2 a high selectivity for large hydrophobic amino acids Phe, Trp and Leu was detected, and in position P2' aliphatic amino acids Leu, Val and Ala was preferred. In positions P3 and P4, N-terminal of the cleaved bond, mMCP-1 showed specificity for aliphatic amino acids. The high selectivity in the P2, P1, P1' and P2' positions indicate that mMCP-1 has a relatively narrow set of in vivo substrates. The consensus sequence was used to screen the mouse protein database for potential substrates. A number of mouse extracellular or membrane proteins were identified and cell adhesion and connective tissue components were a dominating subfamily. This information, including the exact position of potential cleavage sites, can now be used in a more focused screening to identify which of these target molecules is/are responsible for the increased intestinal permeability observed in parasite infected mice.

Up-regulation of intelectin in sheep after infection with Teladorsagia circumcincta.

A novel intelectin molecule designated sheep intelectin 2 (sITLN2) was detected in sheep abomasal mucosa. The full sequence shared 76-83% homology with other mammalian intelectins. Intelectins are mucus-associated proteins that have been shown to be up-regulated in gastrointestinal nematode infections in rodents and in human asthma. Expression of sheep abomasal ITLN2 mRNA was significantly up-regulated on day 10 post-challenge of worm-free sheep with Teladorsagia circumcincta and at day 2 in previously infected, immune sheep. Increased expression of ITLN protein following challenge was confirmed by Western blot and was immunolocalised to the mucous neck cells of the abomasal mucosa. Infection with T. circumcincta was also associated with increased levels of abomasal transcripts encoding sheep mast cell protease-1, ovine galectin-14 and IL4, which collectively suggested a Th2 type response. Intelectin may play an important role in the mucosal response to gastrointestinal nematode infections in ruminants.

Trichinella spiralis induces de novo expression of group IVC phospholipase A2 in the intestinal epithelium.

Phospholipase A2 (PLA2) enzymes play a central role in the initiation, propagation and resolution of inflammation. Here, we describe de novo expression of group IVC PLA2 (PLA2g4c) within the intestinal epithelium of Trichinella spiralis parasitised mice. This mouse mast cell protease-1 sensitive, calcium-independent PLA2 is not detectable in the jejunal epithelium of uninfected mice but becomes highly expressed within the epithelial compartment within days of nematode establishment. We propose that epithelial PLA2g4c accounts for the increased lysophospholipase activity observed during intestinal nematodiasis and that it plays a major role in the inflammatory response to nematodes.

Apical junction complex protein expression in the canine colon: differential expression of claudin-2 in the colonic mucosa in dogs with idiopathic colitis.

Canine idiopathic lymphocytic-plasmacytic colitis (LPC) is a well-recognized clinical and pathological entity in the dog, associated with altered immune cell populations and cytokine expression profiles. Clinical and experimental data indicate that alterations in the permeability of the intestinal epithelium contribute to the pathogenesis of a range of related conditions. The apical junction complex plays a significant role in regulating epithelial paracellular permeability, and we have characterized the distribution of a number of its component tight junction (ZO-1, occludin, claudin-2) and adherens junction (E-cadherin and beta-catenin) proteins in normal colon and colon from dogs with idiopathic LPC. ZO-1, occludin, E-cadherin, and beta-catenin exhibited a distribution in normal canine colon similar to that described previously in humans and rodents. In contrast to the situation in humans, claudin-2-specific labeling was observed in the normal canine colonic crypt epithelium, decreasing in intensity from the distal to the proximal crypt and becoming barely detectable at the luminal surface of the colon. There was little evidence for significant changes in ZO-1, occludin, E-cadherin, or beta-catenin expression in dogs affected by idiopathic LPC. However, claudin-2 expression markedly increased in the proximal crypt and luminal colonic epithelium in affected dogs, suggesting a role in the pathogenesis of canine LPC.

The expression of intelectin in sheep goblet cells and upregulation by interleukin-4.

Upregulation of intelectin (ITLN) transcript and protein has previously been shown in intestinal nematode infections of resistant mice strains with immunolocalisation of protein to goblet cells and paneth cells. In man, intelectin expression has been shown in respiratory tract epithelium, with upregulation occurring in bronchoalveolar lavage fluid of asthmatic individuals. This study describes the expression of intelectin in the respiratory tract of sheep and the immunolocalisation to goblet cells using a novel affinity-purified chicken anti-intelectin peptide antibody. Furthermore we show that when sheep tracheal explants were cultured for 48 h+/- recombinant sheep IL-4, sheep ITLN transcripts were upregulated compared with controls. Putative roles for intelectin have included an antibacterial role and an alteration of the character of mucus. Our data suggest ITLNs may play an important role in the mucosal response in allergy and parasitic infections.

Integrin-alphavbeta6, a putative receptor for foot-and-mouth disease virus, is constitutively expressed in ruminant airways.

Evolved functions of integrin-alpha(v)beta(6) include roles in epithelial cell-extracellular matrix protein interactions and in the binding and activation of latent TGF-beta(1). Integrin-alpha(v)beta(6) is also exploited as a receptor by foot-and-mouth disease virus (FMDV) and may play a significant role in its transmission and pathogenesis. The ovine beta(6) integrin subunit was cloned and sequenced (EMBL accession no. AJ439062). Screening of normal ovine tissues by RT-PCR and immunocytochemistry confirmed that integrin-alphavbeta6 is restricted to sheep epithelial cells. Integrin-alphavbeta6 expression was detected in epithelia of the airways, oral cavity, gastrointestinal tract, kidney, sweat glands, hair follicle sheaths, and the epidermis of pedal coronary band (PB) but not of normal skin. Consistent with FMDV tropism, integrin-alphavbeta6 was detected within the basal layers of the stratified squamous epithelium of the oral mucosa and PB. In addition, integrin-alphavbeta6 appears to be constitutively expressed in the normal airways of both cattle and sheep. The latter finding suggests that ruminant airway epithelium presents a highly accessible target for initiation of infection with FMDV by inhalation.

Primary antibody-Fab fragment complexes: a flexible alternative to traditional direct and indirect immunolabeling techniques.

Immunolabeling with immune complexes of primary and secondary antibodies offers an attractive method for detecting and quantifying specific antigen. Primary antibodies maintain their affinity for specific antigen after labeling with Fab fragments in vitro. Incubation of these immune complexes with excess normal serum from the same species as the primary antibody prevents free Fab fragments from recognizing immunoglobulin. Effectively a hybrid between traditional direct and indirect immunolabeling techniques, this simple technique allows primary antibodies to be non-covalently labeled with a variety of reporter molecules as and when required. Using complexes containing Fab fragments that recognize both the Fc and F(ab')2 regions of IgG, we show that this approach prevents nonspecific labeling of endogenous immunoglobulin, can be used to simultaneously detect multiple antigens with primary antibodies derived from the same species, and allows the same polyclonal antibody to be used for both antigen capture and detection in ELISA.

Evaluation of Th1, Th2 and immunosuppressive cytokine mRNA expression within the colonic mucosa of dogs with idiopathic lymphocytic-plasmacytic colitis.

The objective of this study was to evaluate the expression of the immunoregulatory and pro-inflammatory cytokines interleukin (IL)-2, IL-4, IL-6, IL-12p35, IL-12p40, interferon-gamma (IFN-gamma), and tumour necrosis factor-alpha (TNF-alpha), and the expression of the predominantly immunosuppressive cytokines transforming growth factor-beta (TGF-beta) and IL-10 in canine idiopathic lymphocytic-plasmacytic colitis (LPC). Semi-quantitative reverse transcriptase-polymerase chain reactions were performed using specific primers on RNA isolated from the colonic mucosa of healthy dogs, dogs with clinical signs of large intestinal disease but normal histopathology of the colon, and dogs with LPC. Canine LPC was associated with over-expression of IL-2 compared to healthy colonic mucosa (p<0.01) and the mucosa of dogs with large intestinal diarrhoea but normal histopathology (p<0.05). Higher levels of TNF-alpha mRNA were also seen in LPC compared to healthy mucosa (p<0.05). These results indicate that LPC is associated with activation of CD4+ T-helper lymphocytes and increased production of T-helper-1-type cytokines.

Expression of three intelectins in sheep and response to a Th2 environment.

Sheep intelectin1 and sheep intelectin3 (sITLN1 and sITLN3) were cloned and sequenced. The amino acid sequences of sITLN1 and sITLN3 shared 86% and 91% homology with the previously cloned sheep intelectin2 (sITLN2), respectively. Expression of sITLN1 and sITLN3 transcript was demonstrated in abomasum, lung, colon and gastric lymph node, terminal rectum, skin, jejunum, mesenteric lymph node, ileal peyer's patches, brain, kidney, liver, spleen, skin, ear pinna, heart and ovary in normal sheep tissues. sITLN2 transcript expression was restricted to the abomasal mucosa in normal sheep tissues. Using a non selective chicken anti-intelectin antibody, tissue intelectin protein was demonstrated in mucus neck cells in the abomasum, mucus cells in the colon, free mucus in ileum, goblet cells in the lung, small intestinal epithelium and brush border, epidermal layer of the skin and skin sebaceous glands. The expression of the three sITLN transcripts was examined in two nematode infections in sheep known to induce a Th2 response; a Teladorsagia circumcincta challenge infection model and a Dictyocaulus filaria natural infection. The three sITLN were absent in unchallenged naïve lambs and present in the abomasal mucosa of both naïve and immune lambs following T. circumcincta challenge infection. Upregulation of sITLN2 and sITLN3 was shown in sheep lung following D. filaria natural infection. Intelectins may play an important role in the mucosal response to nematode infections in ruminants.

Proteomic approach to identify candidate effector molecules during the in vitro immune exclusion of infective Teladorsagia circumcincta in the abomasum of sheep.

In the present study we have employed an in vitro organ challenge model to study the post-challenge responses in parasite naïve and immune gastric tissue of sheep, in an attempt to identify the host derived factors involved in immune exclusion of Teladorsagia circumcincta larvae. Proteins present in the epithelial cells and mucus from ovine abomasa following parasite challenge in previously naïve and immune animals were analysed through Matrix Assisted Laser Desorption/Ionization-Time of Flight (MALDI-Tof)-MS and shotgun proteomics. MALDI-ToF analysis of epithelial cell lysates revealed that a number of proteins identified were differentially expressed in naïve and immune cells. These included intelectin and lysozymes, which were present at higher levels in epithelial cell lysates derived from immune samples. A large number of proteins were identified in the mucosal wash from immune tissue which were not present in the mucosal wash of the naïve tissue. Some of these proteins were present in washes of immune tissue prior to the parasite challenge including immunoglobulin A, galectin 14 and 15 and sheep mast cell protease 1. However, other proteins, such as calcium activated chloride channel and intelectin were only detected in the washings from the challenged tissue. The latter may be related to an enhanced mucus release, which may result in entrapment of infective larvae and thus reduced establishment in tissue that has been previously challenged with the parasite. In conclusion, several proteins have been identified which may be involved, either directly or indirectly, in the exclusion and immune elimination of incoming infective larvae. In the present study, the usefulness of the in vitro model has been confirmed, and the global proteomic approach has identified proteins that had not previously been associated with parasite exclusion from abomasal mucosa, such as the calcium activated chloride channel.

Aberrant mucosal mast cell protease expression in the enteric epithelium of nematode-infected mice lacking the integrin alphavbeta6, a transforming growth factor-beta1 activator.

Infection of mice with the nematode Trichinella spiralis triggers recruitment and differentiation of intraepithelial intestinal mucosal mast cells expressing mouse mast cell protease 1 (Mcpt-1), which contributes to expulsion of the parasite. Expression of Mcpt-1 is transforming growth factor (TGF)-beta1-dependent in vitro. TGF-beta1, which is secreted within tissues as a biologically inactive complex with latency-associated peptide, requires extracellular modification to become functionally active. The integrin-alpha(nu)beta(6) mediates local activation of TGF-beta(1) in association with epithelia. Using T. spiralis-infected beta(6)(-/-) mice, we show accumulation of mucosal mast cells in the lamina propria of the small intestine with minimal recruitment into the epithelial compartment. This was accompanied by a coordinate reduction in expression of both Mcpt-1 and -2 in the jejunum and increased tryptase expression, whereas Mcpt-9 became completely undetectable. In contrast, the cytokine stem cell factor, a regulator of mast cell differentiation and survival, was significantly up-regulated in T. spiralis-infected beta(6)(-/-) mice compared with infected beta(6)(+/+) controls. Despite these changes, beta(6)(-/-) mice still appeared to expel the worms normally. We postulate that compromised TGF-beta(1) activation within the gastrointestinal epithelial compartment is a major, but not the only, contributing factor to the observed changes in mucosal mast cell protease and epithelial cytokine expression in beta(6)(-/-) mice.

Anaphylactic release of mucosal mast cell granule proteases: role of serpins in the differential clearance of mouse mast cell proteases-1 and -2.

The granule-derived mouse mast cell proteases-1 and -2 (mMCP-1 and -2) colocalize in similar quantities in mucosal mast cells but micrograms of mMCP-1 compared with nanograms of mMCP-2 are detected in peripheral blood during intestinal nematode infection. This differential systemic response was investigated both in vitro and in vivo. Bone marrow-derived mucosal mast cell homologs released similar quantities of mMCP-1 and-2 concomitantly with beta-hexosaminidase in response to calcium ionophore ( approximately 60% release) or IgE/DNP (25% release). In contrast, serum from mice sensitized by infection with Nippostrongylus brasiliensis 10 days earlier contained >1500-fold more mMCP-1 (10,130 +/- 1,609 ng/ml) than mMCP-2 (6.4 +/- 1 ng/ml), but, in gut lumen, the difference was approximately 8-fold. After OVA sensitization, >600-fold more mMCP-1 (7,861 +/- 2,209 ng/ml) than mMCP-2 (12.8 +/- 4.7 ng/ml) was present in blood 1 h after challenge, but, in gut lumen, there were relatively comparable levels of mMCP-1 and -2. To estimate the rates of systemic accumulation and clearance, 10 microg of mMCP-1 or -2 was injected i.p. Plasma levels of injected mMCP-2 peaked (1%) at 15 min then declined, whereas levels of mMCP-1 were maximal (approximately 25%) at 3 h. Inactivation of mMCP-1 with PMSF before injection resulted in mMCP-2-like kinetics, but inhibition of mMCP-1 by serum gave kinetics similar to that of native mMCP-1. mMCP-1 isolated from serum is complexed with serpins and we conclude that both the accumulation and the longevity of mMCP-1 in blood is due to complex formation, protecting it from a pathway that rapidly clears mMCP-2, which is unable to form complexes with serpins.

The proteome of mouse mucosal mast cell homologues: the role of transforming growth factor beta1.

Mast cells migrate to the mucosal epithelium during intestinal nematode infections in mice, where they express abundant mucosal mast cell-specific proteases, mouse mast cell protease-1 and -2 (MCPT1 and MCPT2). Expression of these proteases is strictly controlled by transforming growth factor-beta1 (TGF-beta1) in the epithelium. In vitro homologues of mucosal mast cells are generated by culturing bone marrow-derived mast cells (BMMC) in the presence of TGF-beta1. We examined the proteome of BMMC cultured either in the presence of TGF-beta1 (n = 5) or of a neutralising anti-TGF-beta1 antibody (n = 5). Cell extracts were examined by 2-DE, and changes in expression levels of protein spots were determined by densitometry. Spots of interest were identified by tryptic peptide mapping. In addition to the up-regulation of MCPT1 and MCPT2, which accounted for approximately 40% of all soluble protein in the TGF-beta1 treated cells, MCPT7 was modestly up-regulated by TGF-beta1, and calnexin was up-regulated fivefold. A 7.6-fold down-regulation of galectin-1 was verified by Western blotting and FACS analysis. Galectin-1 is located on the cell surface where it mediates cellular adhesion to basement membranes. Regulation of its expression by TGF-beta1 may be of relevance to mast cell adhesion within the epithelium.

Lymphocyte-independent connective tissue mast cells populate murine synovium.

OBJECTIVE: Mast cells (MCs) are a heterogeneous population of tissue-resident bone marrow-derived cells; distinct MC subpopulations are situated at specific microanatomic locations. The phenotype of the murine synovial MC remains undefined. Since MCs have been implicated in the pathogenesis of inflammatory arthritis, we sought to define the phenotype of the murine synovial MC population in normal and arthritic joints. We also examined the contribution of lymphocytes to synovial MC physiology. METHODS: The MC phenotype in healthy and K/BxN serum transfer-induced arthritic synovial tissue was defined using immunohistochemical staining of prototypic MC-specific proteases (murine MC proteases [mMCP] 1, 2, 4, 5, 6, and 7) (chymases and tryptases). MC numbers and density were determined by histomorphometry in healthy and arthritic synovia. The lymphocyte contribution to MC populations was assessed using RAG-null mice. RESULTS: We found that synovial MCs display a connective tissue mast cell (CTMC) phenotype in both normal and arthritic synovial tissue, which expresses mMCP-4, -5, -6, and -7, but not mMCP-1 or mMCP-2. In addition, MC hyperplasia was seen in the arthritic synovium. In RAG-null mice, the phenotype and degree of MC hyperplasia were identical to those observed in normal mice with and without arthritis. Furthermore, in contrast to skin CTMCs, all synovial MCs expressed mMCP-6, demonstrating discrete differences between synovial CTMCs and other anatomic CTMC populations. CONCLUSION: Our findings demonstrate that the murine synovial MC population is composed of lymphocyte-independent CTMCs and identify arthritic synovium as a model system by which to gain insight into the poorly understood physiology of CTMCs in chronic inflammation.

Tissue-specific expression of mast cell granule serine proteinases and their role in inflammation in the lung and gut.

Serine proteinases with trypsin-like (tryptase) and chymotrypsin-like (chymase) properties are major constituents of mast cell granules. Several tetrameric tryptases with differing specificities have been characterized in humans, but only a single chymase. In other species there are larger families of chymases with distinct and narrow proteolytic specificities. Expression of chymases and tryptases varies between tissues. Human pulmonary and gastrointestinal mast cells express chymase at lower levels than tryptase, whereas rodent and ruminant gastrointestinal mast cells express uniquely mucosa-specific chymases. Local and systemic release of chymases and tryptases can be quantified by immunoassay, providing highly specific markers of mast cell activation. The expression and constitutive extracellular secretion of the mucosa-specific chymase, mouse mast cell proteinase-1 (mMCP-1), is regulated by transforming growth factor-beta1 (TGF-beta1) in vitro, but it is not clear how the differential expression of chymases and tryptases is regulated in other species. Few native inhibitors have been identified for tryptases but the tetramers dissociate into inactive subunits in the absence of heparin. Chymases are variably inhibited by plasma proteinase inhibitors and by secretory leucocyte protease inhibitor (SLPI) that is expressed in the airways. Tryptases and chymases promote vascular permeability via indirect and possibly direct mechanisms. They contribute to tissue remodelling through selective proteolysis of matrix proteins and through activation of proteinase-activated receptors and of matrix metalloproteinases. Chymase may modulate vascular tissues through its ability to process angiotensin-I to angiotensin-II. Mucosa-specific chymases promote epithelial permeability and are involved in the immune expulsion of intestinal nematodes. Importantly, granule proteinases released extracellularly contribute to the recruitment of inflammatory cells and may thus be involved in innate responses to infection.

Proteomic analysis of mouse jejunal epithelium and its response to infection with the intestinal nematode, Trichinella spiralis.

Infection with the intestinal nematode Trichinella spiralis induces profound, but stereotypic pathological changes to the epithelium, which are common to many nematode infections. This study describes changes in jejunal epithelial protein expression that reflect these stereotypic responses. Adult male BALB/c mice were infected with T. spiralis, and groups (n = 4) examined on day 14/15 (time of worm rejection) were compared with uninfected controls (n = 4). Jejunal epithelium was harvested and extracted for two-dimensional gel electrophoresis. Tryptic peptide mass fingerprinting was used to create a reference map consisting of a total of 52 landmark spots. Of these, 16 were observed to change in intensity during infection. The changes observed at day 14/15 were of relevance to such mechanisms as lipid utilization and transport (increase in triacylglycerol lipase, and reduction in intestinal fatty acid binding protein) and innate immunity (appearance of intelectin-2). As a result, candidate molecules have been identified for further focused studies on their role in the host response to intestinal nematode infection.

Enteric expression of the integrin alpha(v)beta(6) is essential for nematode-induced mucosal mast cell hyperplasia and expression of the granule chymase, mouse mast cell protease-1.

The immunoregulatory cytokine transforming growth factor (TGF)-beta(1) is secreted as a biologically inactive complex with latency-associated peptide, which must be modified by local factors to expose the functionally active cytokine. The epithelial integrin alpha(v)beta(6) mediates local activation of TGF-beta(1) in the lung and beta(6)(-/-) mice exhibit exaggerated pulmonary inflammation, but their response to inflammatory stimuli in the gut has not been investigated. We found that both beta(6) and TGF-beta(1) are constitutively expressed in the jejunal epithelial compartment in uninfected mice and during infection with the intestinal nematode Nippostrongylus brasiliensis. We also present data showing that beta(6)(-/-) mice are seriously compromised in their ability to mount a mucosal mast cell response after infection, and there is a significant reduction in the expression and systemic release of the granule chymase, mouse mast cell protease-1. Because in vitro expression of this chymase is regulated by TGF-beta(1), these data indicate that in the absence of alpha(v)beta(6) epithelially expressed TGF-beta(1) may not be activated, with a consequent absence of expression of mouse mast cell protease-1 and down-regulation of the mucosal mast cell response.