Constitutive expression of mouse mast cell protease-1 in normal BALB/c mice and its up-regulation during intestinal nematode infection

The Chymase Mouse Mast Cell Protease-4 Regulates Intestinal Cytokine Expression in Mature Adult Mice Infected with Giardia intestinalis

Mast cells have been shown to affect the control of infections with the protozoan parasite Giardia intestinalis. Recently, we demonstrated that Giardia excretory-secretory proteins inhibited the activity of the connective tissue mast cell-specific protease chymase. To study the potential role of the chymase mouse mast cell protease (mMCP)-4 during infections with Giardia, mMCP-4^+/+ and mMCP-4^−/− littermate mice were gavage-infected with G. intestinalis trophozoites of the human assemblage B isolate GS. No significant changes in weight gain was observed in infected young (≈10 weeks old) mMCP-4^−/− and mMCP-4^+/+ littermate mice. In contrast, infections of mature adult mice (>18 weeks old) caused significant weight loss as compared to uninfected control mice. We detected a more rapid weight loss in mMCP-4^−/− mice as compared to littermate mMCP-4^+/+ mice. Submucosal mast cell and granulocyte counts in jejunum increased in the infected adult mMCP-4^−/− and mMCP-4^+/+ mice. This increase was correlated with an augmented intestinal trypsin-like and chymotrypsin-like activity, but the myeloperoxidase activity was constant. Infected mice showed a significantly lower intestinal neutrophil elastase (NE) activity, and in vitro, soluble Giardia proteins inhibited human recombinant NE. Serum levels of IL-6 were significantly increased eight and 13 days post infection (dpi), while intestinal IL-6 levels showed a trend to significant increase 8 dpi. Strikingly, the lack of mMCP-4 resulted in significantly less intestinal transcriptional upregulation of IL-6, TNF-α, IL-25, CXCL2, IL-2, IL-4, IL-5, and IL-10 in the Giardia-infected mature adult mice, suggesting that chymase may play a regulatory role in intestinal cytokine responses.

Mast cell chymase decreases the severity of group B Streptococcus infections

BACKGROUND

Group B Streptococcus (GBS) or Streptococcus agalactiae are β-hemolytic gram-positive bacteria that colonize the lower genital tracts of women and are frequently associated with infections during pregnancy. Innate immune defenses are critical for controlling GBS dissemination and systemic infection. Mast cells are resident sentinel cells that come into contact with pathogens early during colonization and infection.

OBJECTIVE

We aimed to investigate the contribution of chymase to systemic GBS infection and rates of preterm birth.

METHODS

Pharmacologic and genetic approaches using mice deficient in mast cell protease (MCPT) 4, the mouse functional homologue of human chymase, were used.

RESULTS

Our studies show that mast cells release a protease with chymotrypsin-like cleavage specificity in response to GBS. Additionally, increased GBS systemic infection and preterm births were observed in MCPT4-deficient mice versus MCPT4-sufficient mice. Furthermore, we observed that proteolytic cleavage of the host extracellular matrix protein fibronectin by peritoneal cell-derived mast cell lysates diminished GBS adherence. Consistent with this observation, the increase in GBS dissemination and preterm births observed in MCPT4-deficient mice was abolished when GBS was deficient in expression of the fibronectin-binding protein SfbA.

CONCLUSIONS

Taken together, our results suggest that the protective effect of MCPT4 against GBS dissemination and preterm labor can be attributed in part to MCPT4-mediated proteolysis of fibronectin. Our studies reveal a novel role of mast cells in defense against bacterial infections.

Globule Leukocytes and Other Mast Cells in the Mouse Intestine

Only 2 major mast cell (MC) subtypes are commonly recognized in the mouse: the large connective tissue mast cells (CTMCs) and the mucosal mast cells (MMCs). Interepithelial mucosal inflammatory cells, most commonly identified as globule leukocytes (GLs), represent a third MC subtype in mice, which we term interepithelial mucosal mast cells (ieMMCs). This term clearly distinguishes ieMMCs from lamina proprial MMCs (lpMMCs) while clearly communicating their common MC lineage. Both lpMMCs and ieMMCs are rare in normal mouse intestinal mucosa, but increased numbers of ieMMCs are seen as part of type 2 immune responses to intestinal helminth infections and in food allergies. Interestingly, we found that increased ieMMCs were consistently associated with decreased mucosal inflammation and damage, suggesting that they might have a role in controlling helminth-induced immunopathology. We also found that ieMMC hyperplasia can develop in the absence of helminth infections, for example, in Treg-deficient mice, Arf null mice, some nude mice, and certain graft-vs-host responses. Since tuft cell hyperplasia plays a critical role in type 2 immune responses to intestinal helminths, we looked for (but did not find) any direct relationship between ieMMC and tuft cell numbers in the intestinal mucosa. Much remains to be learned about the differing functions of ieMMCs and lpMMCs in the intestinal mucosa, but an essential step in deciphering their roles in mucosal immune responses will be to apply immunohistochemistry methods to consistently and accurately identify them in tissue sections.

Proteome analysis of mast cell releasates reveals a role for chymase in the regulation of coagulation factor XIIIA levels via proteolytic degradation

BACKGROUND

Mast cells are significantly involved in IgE-mediated allergic reactions; however, their roles in health and disease are incompletely understood.

OBJECTIVE

We aimed to define the proteome contained in mast cell releasates on activation to better understand the factors secreted by mast cells that are relevant to the contribution of mast cells in diseases.

METHODS

Bone marrow-derived cultured mast cells (BMCMCs) and peritoneal cell-derived mast cells were used as "surrogates" for mucosal and connective tissue mast cells, respectively, and their releasate proteomes were analyzed by mass spectrometry.

RESULTS

Our studies showed that BMCMCs and peritoneal cell-derived mast cells produced substantially different releasates following IgE-mediated activation. Moreover, we observed that the transglutaminase coagulation factor XIIIA (FXIIIA) was one of the most abundant proteins contained in the BMCMC releasates. Mast cell-deficient mice exhibited increased FXIIIA plasma and activity levels as well as reduced bleeding times, indicating that mast cells are more efficient in their ability to downregulate FXIIIA than in contributing to its amounts and functions in homeostatic conditions. We found that human chymase and mouse mast cell protease-4 (the mouse homologue of human chymase) had the ability to reduce FXIIIA levels and function via proteolytic degradation. Moreover, we found that chymase deficiency led to increased FXIIIA amounts and activity, as well as reduced bleeding times in homeostatic conditions and during sepsis.

CONCLUSIONS

Our study indicates that the mast cell protease content can shape its releasate proteome. Moreover, we found that chymase plays an important role in the regulation of FXIIIA via proteolytic degradation.

Anti-Eimeria activity of berberine and identification of associated gene expression changes in the mouse jejunum infected with Eimeria papillata

Plant-based natural products are promising sources for identifying novel agents with potential anti-Eimeria activity. This study explores possible effects of berberine on Eimeria papillata infections in the jejunum of male Swiss albino mice. Berberine chloride, when daily administered to mice during infection, impairs intracellular development and multiplication of E. papillata, evidenced as 60% reduction of maximal fecal output of oocysts on day 5 p.i. Concomitantly, berberine attenuates the inflammatory response, evidenced as decreased messenger RNA (mRNA) expression of IL-1β, IL-6, TNFα, IFNγ, and iNOS, as well as the oxidative stress response, evidenced as impaired increase in malondialdehyde, nitrate, and H2O2 and as prevented decrease in glutathione and catalase activity. Berberine also alters gene expression in the infected jejunum. On day 5 p.i., mRNA expression of 29 genes with annotated functions is more than 10-fold upregulated and that of 14 genes downregulated. Berberine downregulates the genes Xaf1, Itgb3bp, and Faim3 involved in apoptotic processes and upregulates genes involved in innate immune responses, as e.g., Colec11, Saa2, Klra8, Clec1b, and Crtam, especially the genes Cpa3, Fcer1a, and Mcpt1, Mcpt2, and Mcpt4 involved in mast cell activity. Additionally, 18 noncoding lincRNA species are differentially expressed more than 10-fold under berberine. Our data suggest that berberine induces hosts to exert anti-Eimeria activity by attenuating the inflammatory and oxidative stress response, by impairing apoptotic processes, and by activating local innate immune responses and epigenetic mechanisms in the host jejunum. Berberine has the potential as an anti-Eimeria food additive in animal farming.

An IgE receptor mimetic peptide (PepE) protects mice from IgE mediated anaphylaxis

Crosslinking of receptor-bound Immunoglobulin E (IgE) triggers immediate hypersensitivity reactions including anaphylaxis. Blocking the interaction of IgE with its high-affinity receptor, FcεRI, on mast cells and basophils is an attractive strategy for the treatment of allergies. This approach has seen clinical success using the anti-IgE monoclonal antibody, omalizumab. We recently designed and characterized a novel FcεRI-mimetic peptide (PepE) which contains the two key FcεRI α-chain receptor loops known to interact with the ε-heavy chain of IgE, C'-E and B-C, with an optimized linker for joining them. PepE has high specificity and affinity for IgE, blocks IgE binding to FcεRI and prevents IgE-induced mediator release from RBL2H3 cells. We have now investigated the biological effects of this peptide in vivo using a line of mice (BALB/c Il4raF709) very sensitive to IgE-mediated systemic anaphylaxis. IgE-deficient (IgE-/-) Il4raF709 mice were passively sensitized with the anti-DNP IgE monoclonal antibody (SPE-7) and subsequently challenged i.v. with DNP-BSA. Mice receiving a single dose of PepE prior to sensitization with SPE-7 IgE were fully protected from anaphylaxis while vehicle control-treated mice displayed strong reactions with significant core body temperature drops and elevated levels of mouse mast cell protease-1 (mMCP-1) in the serum. However, PepE had no effect on IgE-mediated anaphylaxis if given after IgE administration in IgE-/- mice, suggesting that PepE can block binding of free IgE to FcεRI but cannot compete with the receptor for already bound IgE in vivo. A single dose of PepE treatment did not protect IgE sufficient mice from IgE mediated anaphylaxis. However, a 3 week long course of PepE treatment protected IgE sufficient Il4raF709 mice from body temperature drops and elevation of serum mMCP-1. Our findings establish the potential of this type of structure for blocking IgE binding to mast cells in vivo and suggest that related peptides might have the potential to attenuate clinical allergic reactions.

Development of mast cells and importance of their tryptase and chymase serine proteases in inflammation and wound healing

Mast cells (MCs) are active participants in blood coagulation and innate and acquired immunity. This review focuses on the development of mouse and human MCs, as well as the involvement of their granule serine proteases in inflammation and the connective tissue remodeling that occurs during the different phases of the healing process of wounded skin and other organs. The accumulated data suggest that MCs, their tryptases, and their chymases play important roles in tissue repair. While MCs initially promote healing, they can be detrimental if they are chronically stimulated or if too many MCs become activated at the same time. The possibility that MCs and their granule serine proteases contribute to the formation of keloid and hypertrophic scars makes them potential targets for therapeutic intervention in the repair of damaged skin.

Mast cell proteases as protective and inflammatory mediators

Proteases are the most abundant class of proteins produced by mast cells. Many of these are stored in membrane-enclosed intracellular granules until liberated by degranulating stimuli, which include cross-linking of high affinity IgE receptor F(c)εRI by IgE bound to multivalent allergen. Understanding and separating the functions of the proteases is important because expression differs among mast cells in different tissue locations. Differences between laboratory animals and humans in protease expression also influence the degree of confidence with which results obtained in animal models of mast cell function can be extrapolated to humans. The inflammatory potential of mast cell proteases was the first aspect of their biology to be explored and has received the most attention, in part because some of them, notably tryptases and chymases, are biomarkers of local and systemic mast cell degranulation and anaphylaxis. Although some of the proteases indeed augment allergic inflammation and are potential targets for inhibition to treat asthma and related allergic disorders, they are protective and even anti-inflammatory in some settings. For example, mast cell tryptases may protect from serious bacterial lung infections and may limit the "rubor" component of inflammation caused by vasodilating neuropeptides in the skin. Chymases help to maintain intestinal barrier function and to expel parasitic worms and may support blood pressure during anaphylaxis by generating angiotensin II. In other life-or-death examples, carboxypeptidase A3 and other mast cell peptidases limit systemic toxicity of endogenous peptideslike endothelin and neurotensin during septic peritonitis and inactivate venom-associated peptides. On the other hand, mast cell peptidase-mediated destruction of protective cytokines, like IL-6, can enhance mortality from sepsis. Peptidases released from mast cells also influence nonmast cell proteases, such as by activating matrix metalloproteinase cascades, which are important in responses to infection and resolution of tissue injury. Overall, mast cell proteases have a variety of roles, inflammatory and anti-inflammatory, protective and deleterious, in keeping with the increasingly well-appreciated contributions of mast cells in allergy, tissue homeostasis and innate immunity.

Mast cells regulate homeostatic intestinal epithelial migration and barrier function by a chymase/Mcpt4-dependent mechanism

Altered intestinal barrier function is postulated to be a central predisposing factor to intestinal diseases, including inflammatory bowel diseases and food allergies. However, the mechanisms involved in maintaining homeostatic intestinal barrier integrity remain undefined. In this study, we demonstrate that mice deficient in mast cells (Kit(W-sh/W-sh) [Wsh]) or mast cell chymase (Mcpt4(-/-)) have significantly decreased basal small intestinal permeability compared with wild-type (WT) mice. Altered intestinal barrier function was linked to decreased intestinal epithelial cell migration along the villus/crypt axis, altered intestinal morphology, and dysregulated claudin-3 crypt expression. Remarkably, engraftment of Wsh mice with WT but not Mcpt4(-/-) mast cells restored intestinal epithelial cell migration, morphology, and intestinal epithelial barrier function. Collectively, these findings identify a mechanism by which mast cells regulate homeostatic intestinal epithelial migration and barrier function.

Serglycin proteoglycan: regulating the storage and activities of hematopoietic proteases

Serglycin (SG), like all other proteoglycans, consists of a protein "core" to which sulfated and thereby negatively charged polysaccharide chains of glycosaminoglycan type are attached. The recent generation of mice lacking a functional SG gene has revealed a number of biological functions of SG. In particular, it has been shown that SG has a key role in promoting the storage and in regulating the activities of a number of proteases expressed in hematopoietic cell types, most notably various mast cell proteases. In this review, we summarize the recent development in our understanding of the biological function of SG, in particular by focusing on the novel insight provided through analysis of the SG-deficient mouse strain.

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.

Mast cell production of IL-4 and TNF may be required for protective and pathological responses in gastrointestinal helminth infection

Expulsion of the gastrointestinal nematode Trichinella spiralis is associated with Th2 responses and intestinal inflammation, which correlate with a marked mast cell (MC) response. To address the role of MC-derived cytokines in the induction of protective responses, WBB6F1-KitW/KitW-v (W/W(v)) mice were reconstituted with wild-type, tumor necrosis factor (TNF)-alpha(-/-), or interleukin (IL)-4(-/-) bone marrow (BM) prior to infection with T. spiralis. W/W(v) mice reconstituted with TNF-alpha(-/-) or IL-4(-/-) BM expelled the parasite less efficiently and showed diminished enteropathy, whereas protective responses were normal in W/W(v) mice reconstituted with wild-type BM and were accompanied by intestinal pathology. MC responses were reduced in W/W(v) mice reconstituted with IL-4(-/-) BM and to a lesser extent when reconstituted with TNF-alpha(-/-). These results suggest that MC-derived IL-4 and TNF may regulate the induction of protective Th2 responses and intestinal inflammation associated with the expulsion of T. spiralis. Significantly, these studies suggest a role for MC-derived cytokines as autocrine growth factors.

Serglycin proteoglycan is required for secretory granule integrity in mucosal mast cells

SG (serglycin) PGs (proteoglycans) are strongly implicated in the assembly of MC (mast cell) granules. However, this notion has mainly been on the basis of studies of MCs of the connective tissue subtype, whereas the role of SG PG in mucosal MCs has not been explored. In the present study, we have addressed the latter issue by using mice with an inactivated SG gene. Bone marrow cells were differentiated in vitro into the mucosal MC phenotype, expressing the markers mMCP (mouse MC protease) -1 and -2. Biosynthetic labelling experiments performed on these cells revealed an approximately 80% reduction of 35SO4(2-) incorporation into PGs recovered from SG-/- cells as compared with SG+/+ counterparts, indicating that SG is the dominating cell-associated PG of mucosal MCs. Moreover, the absence of SG led to defective metachromatic staining of mucosal MCs, both in vivo and in the in vitro-derived mucosal MCs. Ultrastructural analysis showed that granules were present in similar numbers in SG+/+ and SG-/- cells, but that their morphology was markedly affected by the absence of SG, e.g. with electron-dense core formation only seen in SG+/+ granules. Analysis of the MC-specific proteases showed that mMCP-1 and mMCP-7 were completely independent of SG for storage, whereas mMCP-2 showed a partial dependence. In contrast, mMCP-4 and -6, and carboxypeptidase A were strongly dependent on SG for storage. Together, our data indicate that SG PG is of crucial importance for assembly of mature mucosal MC granules, but that the specific dependence on SG for storage varies between individual granule constituents.

Progress in the molecular biology of malaria and the immunology of nematode infections

Japan is one of a small number of countries to have successfully controlled or eliminated major parasitic diseases, including malaria, filariasis, schistosomiasis and enteric parasitoses. Of particular importance in this success was a close collaboration between primary research and public health efforts. Many Japanese researchers continue to study malaria, particularly the areas of genetics and immunology, and this should contribute to global parasite eradication strategies. Furthermore, studies of immunoregulation of nematode infection using the interleukin-18 pathway, most of which have been conducted in Japan, are helping to improve researchers' understanding of human immune mechanisms and host-parasite interactions.

Proteinase inhibitors and helminth parasite infection

The concept that parasites may utilize proteinase inhibitors to survive within the host has been with us for 100 years. Given that we now know that proteinases are involved in key areas of the host anti-parasite immune response including antigen presentation, effector cell function and tissue dissolution and remodelling, it is somewhat surprising that the proteinase inhibitors of parasite origin have not generally been the subject of intense research effort. There is now substantial evidence to show that nematode parasites utilize these inhibitors to protect themselves from degradation by host proteinases, to facilitate feeding and to manipulate the host response to the parasite. The diversity of the parasite-derived inhibitors is also being revealed and they target the four major proteinase classes, namely serine, cysteine, aspartic and metallo-proteinases. This review summarizes the information available on nematode-derived proteinase inhibitors and what is known of their putative functions. Their potential as targets for immunological control is also addressed.

Evaluating the effectiveness of a Mexican strain ofDuddingtonia flagransas a biological control agent against gastrointestinal nematodes in goat faeces

The use ofDuddingtonia flagransin the control of goat nematodes was investigated. Initially, the time of passage of chlamydospores through the digestive tract of goats was evaluated. Two groups of seven parasite-free kids were formed. Group A received a single dose of 3.5×106D. flagranschlamydospores (FTHO-8 strain) per kg of live weight. Group B did not receive any chlamydospores. Faeces were obtained from each kid daily from day 4 prior to inoculation until day 5 post-inoculation (PI) and were placed in Petri dishes containing water agar. Gastrointestinal nematode infective larvae were added to each Petri dish and incubated at 25°C for 7 days. Petri dishes were examined to detect the fungus and trapped nematodes. A second trial evaluated the effect ofD. flagranson the number of gastrointestinal nematode larvae harvested from goat faecal cultures in naturally infected goats. Two groups of seven goats were formed. The treated group received a single dose of 3.5×106D. flagranschlamydospores per kg of liveweight. The control group did not receive any chlamydospores. Faeces were obtained twice daily from each kid. Two faecal cultures were made for each kid. One was incubated for 7 days and the other for 14 days. Gastrointestinal nematode larvae were recovered from each culture and counted. Percentage of larval development reduction was determined using a ratio of larvae/eggs deposited in the control and treated groups.Duddingtonia flagranssurvived the digestive process of goats, and maintained its predatory activity, being observed from 21 to 81 h PI (3 to 4 days). A reduction in the infective larvae population in the treated group compared to the non-treated group was observed in both incubation periods (7 days: 5.3–36.0%; 14 days: 0–52.8%,P>0.05). Although a single inoculation ofD. flagranscan induce a reduction of infective larvae collected from faeces, a different scheme of dosing may be needed to enhance the efficacy ofD. flagransin goats.

Mast Cell Proteases

Mast cells (MCs) are traditionally thought of as a nuisance for its host, for example, by causing many of the symptoms associated with allergic reactions. In addition, recent research has put focus on MCs for displaying harmful effects during various autoimmune disorders. On the other hand, MCs can also be beneficial for its host, for example, by contributing to the defense against insults such as bacteria, parasites, and snake venom toxins. When the MC is challenged by an external stimulus, it may respond by degranulation. In this process, a number of powerful preformed inflammatory "mediators" are released, including cytokines, histamine, serglycin proteoglycans, and several MC-specific proteases: chymases, tryptases, and carboxypeptidase A. Although the exact effector mechanism(s) by which MCs carry out their either beneficial or harmful effects in vivo are in large parts unknown, it is reasonable to assume that these mediators may contribute in profound ways. Among the various MC mediators, the exact biological function of the MC proteases has for a long time been relatively obscure. However, recent progress involving successful genetic targeting of several MC protease genes has generated powerful tools, which will enable us to unravel the role of the MC proteases both in normal physiology as well as in pathological settings. This chapter summarizes the current knowledge of the biology of the MC proteases.

Screening for immunomodulatory proteins of the intestinal parasitic nematode Heligmosomoides polygyrus

Parasitic nematodes are constantly exposed to the immune effector mechanisms of their hosts. One strategy of the worms to cope with these defence reactions is the secretion of modulatory proteins that down-regulate cell-mediated immune responses. We analysed the proliferation of mesenteric lymph node cells of mice infected with Heligmosomoides polygyrus and showed that cellular proliferation was strongly suppressed in the chronic phase of infection. To identify proteins of H. polygyrus that are involved in parasite-induced immunomodulation, worm extract and culture supernatant of adult H. polygyrus were fractionated by gel chromatography and activity of each fraction was determined. One of the fractions (fraction 9) of worm extract as well as worm secretory products inhibited the antigen-specific cellular proliferation by about 40%. This reduced cellular reactivity coincided with a down-regulation of inducible nitric oxide production of mouse macrophages by 57%. Furthermore, fraction 9 contained antigens that were recognized by IgE antibodies of H. polygyrus-infected mice and induced degranulation of an IgE-sensitized basophil cell line. Single proteins of fraction 9 were analysed by mass spectrometry. These data suggest that antigens that are recognised by IgE antibodies might play an important role in immunomodulation exerted by nematode infections.

Roles of IL-18 in basophils and mast cells

Basophils and mast cells are effecter cells in allergen/IgE-mediated immune responses. They induce type 1 immediate immune response in airway or other organ, resulting in bronchial asthma and other allergic diseases. However, they also play a critical role in host defense against infection with helminthes. Upon linkage of FcepsilonRI with a complex of allergen and IgE, basophils and mast cells release a large amount of Th2 cytokines and chemical mediators. Therefore these responses are "acquired allergic responses" and induce allergic diseases, such as bronchial asthma. However, basophils and mast cells derived from cultured bone marrow cells with IL-3 for 10 days express IL-18Ralpha chain and produce Th2 cytokines in response to the stimulation with IL-3 and IL-18 without FcepsilonRI cross-linkage. Furthermore, they produce Th2 cytokines upon stimulation with several TLR ligands, such as LPS. This finding may suggest the presence of allergen/IgE-independent allergic responses, which we would like to designate as "innate allergic response". However, in vivo treatment with IL-18 and IL-2 protects against gastrointestinal nematode infection by activating intestinal mucosal mast cells in STAT6-independent manner, suggesting the importance of innate allergic response against helminth infection. Here we discuss the functional role of IL-18-induced "innate allergic response" in disease and host defense.

Rapidly changing perspectives about mast cells at mucosal surfaces

Mast cells (MCs) are major effector cells of immunoglobulin E (IgE)-mediated allergic inflammation. However, it has become increasingly clear that they also play important roles in diverse physiological and pathological processes. Recent advances have focused on the importance of MCs in both innate and adaptive immune responses and have fostered studies of MCs beyond the myopic focus on allergic reactions. MCs possess a variety of surface receptors and may be activated by inflammatory mediators, IgE, IgG, light chains, complement fragments, proteases, hormones, neuropeptides, and microbial products. Following activation, they produce a plethora of pro-inflammatory mediators and participate in inflammatory reactions in many organs. This review focuses on the role of MCs in inflammatory reactions in mucosal surfaces with particular emphasis on their role in respiratory and gastrointestinal inflammatory conditions.

IL-18 with IL-2 protects against Strongyloides venezuelensis infection by activating mucosal mast cell-dependent type 2 innate immunity

C57BL/6 (B6) and B6 background STAT6^−/− mice pretreated with IL-18 plus IL-2 showed prominent intestinal mastocytosis and rapidly expelled implanted adult worms of the gastrointestinal nematode Strongyloides venezuelensis. In contrast, identically pretreated mast cell–deficient W/W^v mice failed to do so. Thus, activated mucosal mast cells (MMC) are crucial for parasite expulsion. B6 mice infected with S. venezuelensis third-stage larvae (L3) completed parasite expulsion by day 12 after infection, whereas IL-18^−/− or IL-18Rα^−/− B6 mice exhibited marked impairment in parasite expulsion, suggesting a substantial contribution of IL-18–dependent MMC activation to parasite expulsion. Compared with IL-18^−/− or IL-18Rα^−/− mice, S. venezuelensis L3–infected STAT6^−/− mice have poorly activated MMC and sustained infection; although their IL-18 production is normal. Neutralization of IL-18 and IL-2 further reduces expulsion in infected STAT6^−/− mice. These results suggest that collaboration between IL-18–dependent and Th2 cell–dependent mastocytosis is important for prompt parasite expulsion.

Innate BALB/c Enteric Epithelial Responses to Trichinella spiralis: Inducible Expression of a Novel Goblet Cell Lectin, Intelectin-2, and Its Natural Deletion in C57BL/10 Mice

Infection of mice with the nematode parasite Trichinella spiralis induces changes in the proteome of the jejunal epithelium, including substantial up-regulation of a novel variant of interlectin. In this study we sequence this novel lectin, termed intelectin-2, and compare expression levels during T. spiralis infection of resistant (BALB/c) with susceptible (C57BL/10) mouse strains. Intelectin-2 was cloned and sequenced from BALB/c mRNA extracted on day 14 of infection, and was found to have 91% amino acid identity with intelectin (within our study termed intelectin-1). Intelectin-2 transcripts were up-regulated early (day 3) during infection with T. spiralis in BALB/c mice, suggesting an innate response, and levels remained high through to day 14 (time of parasite rejection). Immunohistochemistry of jejunal sections with a rabbit polyclonal Ab to Xenopus laevis 35-kDa cortical granule lectin (XL35; 68% identity with intelectin-2) followed a similar pattern, with intense labeling of goblet and Paneth cells at day 14. However, intelectin-2 transcripts and protein were absent, and immunohistochemistry negative when C57BL/10 mice were infected with T. spiralis. Genomic PCR and Southern blotting confirmed that the intelectin-2 gene is absent from the C57BL/10 genome. The presence of intelectin-2 in resistant BALB/c mice, its absence from the susceptible C57BL/10 strain and the kinetics of its up-regulation during T. spiralis infection suggest that this novel lectin may serve a protective role in the innate immune response to parasite infection.

Mouse mast cell protease-1 is required for the enteropathy induced by gastrointestinal helminth infection in the mouse

BACKGROUND & AIMS

The relationship between intestinal pathology and immune expulsion of gastrointestinal nematodes remains controversial. Immune expulsion of gastrointestinal helminth parasites is usually associated with Th2 responses, but the effector mechanisms directly responsible for parasite loss have not been elucidated. Mast cell hyperplasia is a hallmark of infection with gastrointestinal nematodes, in particular Trichinella spiralis. Although the precise mechanism by which mast cells induce expulsion of these parasites has not been elucidated, it has been proposed that mast cell mediators, including cytokines and granule chymases, act to create an environment inhospitable to the parasite, part of this being the induction of intestinal inflammation. Therefore, the aims of this study were to dissect the role of mast cells and mast cell proteases in the induction of parasite-induced enteropathy.

METHODS

Mast cell-deficient W/Wv and mouse mast cell protease-1 (mMCP-1)-deficient mice were infected with T. spiralis, and parasite expulsion, enteropathy, and Th2 responses were determined.

RESULTS

Expulsion of the parasite was delayed in both strains of mice compared with wild-type controls; additionally, in both cases, the enteropathy was significantly ameliorated. Although Th2 responses were significantly reduced in mast cell-deficient W/Wv mice, those from mMCP-1-deficient mice were similar to wild-type mice. Additionally, levels of TNF-alpha and nitric oxide were significantly reduced in both W/Wv and mMCP-1 deficient mice.

CONCLUSIONS

These results imply that mast cells may contribute to the induction of protective Th2 responses and, importantly, that the intestinal inflammation associated with gastrointestinal helminths is partly mediated by mMCP-1.

Purification and characterization of mouse mast cell proteinase-2 and the differential expression and release of mouse mast cell proteinase-1 and -2 in vivo

BACKGROUND

Gastrointestinal nematode infection is associated with mucosal mast cell (MMC) hyperplasia. In the mouse, this is accompanied by the release of substantial quantities of the chymase mouse mast cell proteinase-1 (mMCP-1) into the gut lumen and peripheral bloodstream. Expression of mMCP-1 is largely restricted to intraepithelial MMC and is thought to play a role in the regulation of epithelial permeability. MMCs also express mouse mast cell proteinase-2 (mMCP-2), but less is known about the expression or biological function of this proteinase.

OBJECTIVES

(1) To purify and characterize mMCP-2. (2) To compare the expression and release of mMCP-2 and mMCP-1 in vivo using specific antibodies.

METHODS

Bone marrow-derived mast cells (mBMMCs) were generated from mMCP-1(-/-) BALB/c mice. mMCP-2 was purified, characterized and used to generate rat and sheep polyclonal antibodies. The expression and systemic release of mMCP-1 and -2 were compared in vivo by immunohistochemistry and ELISA.

RESULTS

mMCP-2 was successfully purified from mMCP-1(-/-) mBMMC and its identity confirmed by N-terminal amino acid sequencing. mMCP-2 bound [3H]-labelled DFP, indicating the presence of an active serine proteinase catalytic site, but showed little evidence of chymotryptic activity. MMC expressed comparable levels of mMCP-1 and -2 in the jejunum but not in the gastric mucosa, where mMCP-2 was more abundant. Expression of both proteinases increased substantially during primary Nippostrongylus brasiliensis infection and this was accompanied by a substantial increase in peripheral blood levels of mMCP-1 (70 microg/mL on day 12). By contrast, mMCP-2 was not detected in the serum of uninfected mice and only increased to approximately 25 ng/mL on day 12.

CONCLUSION

As in the case of mMCP-1, mMCP-2 expression is restricted to MMC. However, mMCP-2 lacks chymase activity, is expressed at higher levels in gastric MMC and appears to be differentially released into the peripheral bloodstream.

Mucosal mast cells and nematode infection: strain-specific differences in mast cell precursor frequency revisited

Mucosal mast cells (MMC) play an important role in the immune response against selected species of intestinal nematode. The kinetics with which different strains of inbred mice resolve infection with Trichinella spiralis correlates with their ability to mount MMC responses in the intestinal mucosa. Homologues of MMC that express and constitutively secrete abundant amounts of the granule chymase, mouse mast cell protease-1 (mMCP-1), can be generated in vitro from bone marrow cultures supplemented with interleukins-3 and -9, stem cell factor and transforming growth factor-beta1. Using the enhanced growth characteristics of these MMC homologues, a novel limiting dilution assay for mast cell precursor (MCp) frequency has been developed. The assay is highly specific, in that cultures containing mast cells are identified with mMCP-1 specific antibody, and almost three-fold more sensitive than previously published systems. MCp frequencies were compared in BALB/c and C57/BL10 strains of mice that, respectively, respond rapidly and slowly to infection with T. spiralis. MCp frequency (1/378 bone marrow cells) was significantly greater in BALB/c than C57/BL10 mice (frequency: 1/751). Similarly the rate of growth of MMC homologues and the production of mMCP-1 was significantly greater in BALB/c than in C57/BL10 bone marrow cultures.

Mouse mast cell protease-1 cleaves angiotensin I to form angiotensin II

The ability to convert angiotensin (Ang) I to Ang II was compared between human alpha-chymase and two mouse beta-chymases, mouse mast cell protease (mMCP)-1 and mMCP-4. Human chymase hydrolyzed Ang I to produce Ang II without further degradation. mMCP-1 similarly generated Ang II from Ang I in a time-dependent manner and the formation of the fragment other than Ang II was marginal. In contrast, mMCP-4 hydrolyzed Ang I at two sites, Tyr(4)-Ile(5) and Phe(8)-His(9), with Ang II formation being tentative. Consistently, mMCP-4 but not human chymase hydrolyzed Ang II and mMCP-1 showed little hydrolytic activity against Ang II. These data suggest that not only human chymase but also mMCP-1 might possess a physiological role in Ang II formation. Our findings also imply that the Ang-converting activity of chymase may not be related to the categorization of chymase into alpha- or beta-type based on their primary structure.

Constitutive secretion of the granule chymase mouse mast cell protease-1 and the chemokine, CCL2, by mucosal mast cell homologues

BACKGROUND

The mucosal mast cell (MMC) granule-specific beta-chymase, mouse mast cell protease-1 (mMCP-1), is released systemically into the bloodstream early in nematode infection before parasite-specific IgE responses develop and TGF-beta1 induces constitutive release of mMCP-1 by homologues of MMC in vitro. Intraepithelial MMC may also express the chemokine CCL2 (monocyte chemotactic protein-1) during nematode infection but the expression of this chemokine by MMC homologues has not been investigated.

OBJECTIVE

To investigate the expression and to compare the mechanisms of constitutive release of the chymase, mMCP-1, and the chemokine, CCL2.

METHODS

MMC homologues were generated by culturing bone marrow cells in the presence of TGF-beta1, IL-3, IL-9 and stem cell factor (SCF). The intracellular distribution of mMCP-1 and CCL2 was examined by confocal microscopy. The involvement of the Golgi complex and of protein synthesis in the constitutive release of mMCP-1 and CCL2 was investigated using the Golgi-disrupting agent brefeldin A and cycloheximide to block protein synthesis. Secreted analytes were quantified by ELISA.

RESULTS

mMCP-1 colocalized with Golgi matrix protein 130 but was most abundant in the granules, whereas CCL2 was not found in the granules but appeared to be located uniquely in the Golgi complex. Extracellular release of mMCP-1 was significantly inhibited ( approximately 40%) by cycloheximide and by the Golgi-disrupting agent brefeldin A, indicating both continuous protein synthesis and transportation via the Golgi complex are required for optimal mMCP-1 secretion. A similar but more marked inhibitory effect with both compounds was demonstrated on the constitutive secretion of CCL2.

CONCLUSION

The culture conditions that promote mMCP-1 expression and release by MMC homologues also promote the expression and release of CCL2. Constitutive release involves de novo protein synthesis and requires a functional Golgi complex, suggesting that similar mechanisms of extracellular secretion operate for both mediators.

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.

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.

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.

Transforming growth factor-beta1 mediates coexpression of the integrin subunit alphaE and the chymase mouse mast cell protease-1 during the early differentiation of bone marrow-derived mucosal mast cell homologues

BACKGROUND

Mucosal mast cells (MMC) play a central role in gut hypersensitivities and inflammation. They are morphologically, biochemically and functionally distinct from their connective tissue counterparts. Massive hyperplasia of MMC occurs 7-10 days after intestinal infection with nematodes but it has never been possible to replicate this phenomenon in vitro.

OBJECTIVE

(1) To determine whether mouse bone marrow-derived mast cells (mBMMC) grown in the presence of transforming growth factor (TGF)-beta1 could develop over the same time frame (7-10 days) as MMC in parasitized mice. (2) To compare the early expression of surface receptors (integrins alphaE and beta7, c-kit and FcepsilonR) with that of the MMC-specific granule chymase mouse mast cell protease-1 (mMCP-1).

METHODS

Mouse bone marrow cells were cultured in the presence of IL-9, IL-3 and Stem Cell Factor (SCF) with or without TGF-beta1. mBMMC were quantified after toluidine blue or Leishmans' staining. Expression of MMC-specific mouse mast cell proteases was analysed by ELISA, immunohistochemistry and RT-PCR. Surface antigen expression was characterized by flow cytometry and confocal microscopy.

RESULTS

TGF-beta1 promotes the development of abundant MMC-like mBMMC from bone marrow progenitor cells with kinetics, which closely parallel that seen in vivo. mRNA transcripts encoding mMCP-1 and -2 are readily detectable by day 4 ex vivo in cultures grown in the presence of TGF-beta1. Between 30 and 40% and 75-90% of the cells in these cultures on days 4 and 7, respectively, have typical mast cell morphology, are c-kit+, FcepsilonR+, integrin alphaEbeta7+, and express and secrete abundant mMCP-1. The integrin alphaE subunit is coexpressed with mMCP-1.

CONCLUSION

The kinetics of mMCP-1+/alphaE+ mBMMC development, regulated by TGF-beta1, are consistent with that seen in vivo in the parasitized intestine. The normally down-regulatory functions of TGF-beta1 in haematopoiesis are superseded in this culture system by its ability to promote the early expression of alphaE and mMCP-1.

Gastrointestinal nematodes, nutrition and immunity: breaking the negative spiral

Nutritionists have long understood that intestinal nematode parasites have deleterious effects on host nutritional status, but only recently has the importance of malnutrition as a predisposing factor to intestinal nematodes been recognized. Here we review experimental and field studies on the effects of protein, energy, zinc, vitamin A, and iron deficiencies on gastrointestinal (GI) nematodes of humans, livestock, and laboratory rodents, and draw certain conclusions about the state of our current understanding. In general, malnutrition promotes the establishment, survival, and fecundity of these parasites, but the magnitude of the effect depends on factors such as host species, parasite species, particular infection protocol used, magnitude of the infection, severity of the nutritional deficiency, and presence of single or multiple infections and single or multiple nutritional deficiencies. We highlight the Th2 arm of the immune system as a component of primary importance in the association between malnutrition and GI nematode infections. We summarize what is known about underlying mechanisms that may account for the observed patterns. Finally, we suggest future research directions.

Delayed expulsion of the nematode Trichinella spiralis in mice lacking the mucosal mast cell-specific granule chymase, mouse mast cell protease-1

Expulsion of gastrointestinal nematodes is associated with pronounced mucosal mast cell (MMC) hyperplasia, differentiation, and activation, accompanied by the systemic release of MMC granule chymases (chymotrypsin-like serine proteases). The beta-chymase mouse mast cell protease-1 (mMCP-1) is expressed predominantly by intraepithelial MMCs, and levels in the bloodstream and intestinal lumen are maximal at the time of worm expulsion in parasitized mice. To address the in vivo functions of MMC-specific beta-chymases, we have generated transgenic mice that lack the mMCP-1 gene. They were backcrossed onto a congenic BALB/c background to investigate the response to nematode infection. The deletion of the mMCP-1 gene is associated with significantly delayed expulsion of Trichinella spiralis and increased deposition of muscle larvae in BALB/c mice despite the presence of normal and sometimes increased numbers of MMCs. Neither worm fecundity nor worm burdens were altered in Nippostrongylus-infected mMCP-1(-/)- BALB/c mice. These data demonstrate, for the first time, that the ablation of an MMC-derived effector molecule compromises the expulsion process.

Immunoglobulin E and mast cell responses are related to worm biomass but not expulsion of Hymenolepis diminuta during low dose infection in rats

It is well known that the destrobilation and later expulsion are characteristics of multiple Hymenolepis diminuta infections in rats. This process is suggested to be mediated by a variety of host cellular responses. It has also been suggested that immunoglobulin (Ig) E may have a beneficial role for some cestodes including H. diminuta. We examined the intestinal mast cell and serum IgE responses to a 10-H. diminuta infection in three different rat strains. Tapeworm infection induced no increased mast cell and IgE responses in F344 rats in which neither worm biomass nor worm burden decreased during 6 weeks of observation. The number of mast cells and amounts of serum rat mast cell protease (RMCP) II and IgE markedly increased from 3 weeks postinfection (p.i.) in BN rats. The worm biomass in BN rats was significantly lower than that in F344 rats, but worm burden was not different from that in F344 rats at 3 or 6 weeks p.i. In DA rats, the number of mast cells and levels of serum RMCP II and IgE increased at 6 weeks but not at 3 weeks p.i. Although numbers of mast cells and serum RMCP II and IgE levels were lower in DA rats than in BN rats, smaller and fewer worms were recovered in DA rats than in F344 and BN rats at from 3 and 6 weeks p.i. Worms were recovered from all of F344 and BN rats, while only 40% of DA rats harboured worms at 6 weeks p.i. These results suggested that the worm biomass was related to mast cell and IgE responses, but these responses were not required for worm expulsion during low dose H. diminuta infection in rats.

Mucosal defense against gastrointestinal nematodes: responses of mucosal mast cells and mouse mast cell protease 1 during primary strongyloides venezuelensis infection in FcRgamma-knockout mice

A possible role for the gamma subunit of immunoglobulin Fc receptors (FcR) in mucosal defenses against intestinal nematode parasites was studied using age-matched FcRgamma-knockout (FcRgamma(-/-)) and wild-type (FcRgamma(+/+)) C57BL/6 mice. Mice were infected subcutaneously with 3,000 infective larvae of Strongyloides venezuelensis, and the degree of infection was monitored by daily fecal egg counts and adult worm recovery on days 8 and 13 postinfection. Mucosal mast cell (MMC) responses were assayed by in situ intestinal mast cell counts in stained histological sections of the jejunum and by measuring mouse mast cell protease 1 (MMCP-1) release in serum using sandwich enzyme-linked immunosorbent assay. FcRgamma(-/-) mice had significantly higher egg counts (P<0.01) and numbers of adult worms (P<0.05) than FcRgamma(+/+) mice, but mastocytosis and serum MMCP-1 release were comparable. It was concluded that MMCP-1 release may be spontaneous, does not depend on mast cell degranulation via the FcRgamma signaling system, and appears to play no role in the expulsion of S. venezuelensis. The delay in worm expulsion in the FcRgamma(-/-) mice might be related to inability of the MMC to degranulate and release effector molecules other than MMCP-1, since FcRgamma deletion abrogates mast cell degranulative responses.

Suppressed T helper 2 immunity and prolonged survival of a nematode parasite in protein-malnourished mice

Protein malnutrition may increase susceptibility to gastrointestinal parasitic infections, possibly as a result of impaired intestinal and/or systemic T helper 2 (Th2) effector responses induced by down-regulation of Th2 cytokines and/or up-regulation of Th1 cytokines. To test this hypothesis, female BALB/c mice (n = 18/diet) were fed a control (24%), marginal (7%), or deficient (3%) protein diet and given a challenge infection with Heligmosomoides polygyrus. The 3% mice had higher worm burdens at 1, 2, and 4 weeks postchallenge infection (pci), lower increases in serum IgE, reduced intestinal eosinophilia, and depressed mucosal mast cell proliferation and activation at 1-2 weeks pci. To determine whether these suppressed effector responses resulted from altered spleen and mesenteric lymph node (MLN) cytokine production, cells were restimulated in vitro with parasite antigen and cytokine concentrations were measured. Deficient MLN cells secreted significantly less IL-4 and more IFN-gamma at 1-2 weeks pci than did control MLN cells. Deficient spleen cells also secreted more IFN-gamma at 2 weeks pci compared with control spleen cells. From reverse transcription-PCR analyses, the 3% mice also had lower IL-4 mRNA level in spleen and MLN at 1-2 weeks pci. Our study supports the hypothesis that protein malnutrition increases the survival of a nematode parasite by decreasing gut-associated IL-4 (Th2) and increasing IFN-gamma (Th1) within 2 weeks pci, leading to reduced intestinal and systemic Th2 effector responses.

Zinc deficiency impairs immune responses against parasitic nematode infections at intestinal and systemic sites

Research on the complex interactions among host nutritional status, parasitic infection and immune responsiveness has focused on the detrimental consequences of parasitic infections on host nutritional status and on mechanisms by which malnutrition impairs immunocompetence. Curiously, relatively few studies have examined the effects of malnutrition on the immune response in the parasite-infected host, and even fewer have considered the events occurring at the intestinal level, where absorption of nutrients occurs, intestinal parasites reside, and the gastrointestinal-associated lymphoid tissues play a role in directing both the local and the more systemic immune responses. Our work using a zinc-deficient nematode-infected mouse model reveals that parasites are better able to survive in the zinc-deficient hosts than in well-nourished hosts; that the production of interleukin-4 in the spleen of zinc-deficient mice is depressed, leading to depressed levels of IgE, IgG(1) and eosinophils; and that the function of T cells and antigen-presenting cells is impaired by zinc deficiency as well as by energy restriction. Given the paramount role of the gastrointestinal-associated lymphoid tissues in inducing and regulating immune responses to intestinal parasites and in orchestrating responses in the spleen and peripheral circulation, we conclude that zinc deficiency (in association with energy restriction) exerts profound effects on the gut mucosal immune system, leading to changes in systemically disseminated immune responses and, importantly, to prolonged parasite survival.

Trichuris suis: a secretory chymotrypsin/elastase inhibitor with potential as an immunomodulator

A serine protease inhibitor, termed TsCEI, was purified from adult-stage Trichuris suis by acid precipitation, affinity chromatography (elastase-agarose), and reverse-phase HPLC. The molecular weight of TsCEI was estimated at 6.437 kDa by laser desorption mass spectrometry. TsCEI potently inhibited both chymotrypsin (K(i) = 33.4 pM) and pancreatic elastase (K(i) = 8.32 nM). Neutrophil elastase, chymase (mouse mast cell protease-1, mMCP-1), and cathepsin G were also inhibited by TsCEI, whereas trypsin, thrombin, and factor Xa were not. The cDNA-derived amino acid sequence of the mature TsCEI consisted of 58 residues including 9 cysteine residues with a molecular mass of 6.196 kDa. TsCEI displayed 48% sequence identity to a previously characterized trypsin/chymotrypsin inhibitor of T. suis, TsTCI. TsCEI showed 36% sequence identity to a protease inhibitor from the hemolymph of the honeybee Apis mellifera. Sequence similarity was also detected with the trypsin/thrombin inhibitor of the European frog Bombina bombina, the elastase isoinhibitors of the nematode Anisakis simplex, and the chymotrypsin/elastase and trypsin inhibitors of the nematode Ascaris suum. The inhibitors of T. suis, an intestinal parasite of swine, may function as components of a parasite defense mechanism by modulating intestinal mucosal mast cell-associated, protease-mediated, host immune responses.

Immunology of helminth infections, with special reference to immunopathology

Immune responses resulting in immunity to infection or disease, share the same basic humoral and cellular mechanisms. While immunity to helminth infection has evolved to mediate rapid elimination of the parasite, the strategies evolved by the parasites themselves aim to delay this rejection process and ensure the survival and distribution of their progeny. Ineffective or incomplete immunity results in persistence of parasites or their products within the host tissues, inappropriate or chronic stimulation by parasite antigens, hyper-reactivity and tissue damage or immunopathology. A long standing classification by Gell and Coombs identifies four major types of hypersensitivity responses accounting for most of the immunopathogenesis, three of which are mediated by antibody and one, delayed type hypersensitivity (DTH), by T cells. This paper aims to give a short review of these four classical hypersensitivity reactions with particular reference to infections of large animals with helminth parasites. In addition, in view of the functionally different helper T cell subsets now identified, the existing DTH response is redefined as DTH Type 1 (Th-1 mediated) and two new classes of T cell-dependent DTH responses are proposed; DTH Type II, associated with the Th-2 type cytokines IL-4 and IL-5 and eosinophilic granuloma formation, and DTH Type III, associated with IL-4 and TGF-beta and fibrosis. Finally, some implications of immunopathology on parasite control strategies are discussed.

Inflammatory mast cells up-regulate angiogenesis during squamous epithelial carcinogenesis

Expression of HPV16 early region genes in basal keratinocytes of transgenic mice elicits a multistage pathway to squamous carcinoma. We report that infiltration by mast cells and activation of the matrix metalloproteinase MMP-9/gelatinase B coincides with the angiogenic switch in premalignant lesions. Mast cells infiltrate hyperplasias, dysplasias, and invasive fronts of carcinomas, but not the core of solid tumors, where they degranulate in close apposition to capillaries and epithelial basement membranes, releasing mast-cell-specific serine proteases MCP-4 (chymase) and MCP-6 (tryptase). MCP-6 is shown to be a mitogen for dermal fibroblasts that proliferate in the reactive stroma, whereas MCP-4 can activate progelatinase B and induce hyperplastic skin to become angiogenic in an in vitro bioassay. Notably, premalignant angiogenesis is abated in a mast-cell-deficient (KITW/KITWWv) HPV16 transgenic mouse. The data indicate that neoplastic progression in this model involves exploitation of an inflammatory response to tissue abnormality. Thus, regulation of angiogenesis during squamous carcinogenesis is biphasic: In hyperplasias, dysplasias, and invading cancer fronts, inflammatory mast cells are conscripted to reorganize stromal architecture and hyperactivate angiogenesis; within the cancer core, upregulation of angiogenesis factors in tumor cells apparently renders them self-sufficient at sustaining neovascularization.

A Novel Function for Transforming Growth Factor-β1: Upregulation of the Expression and the IgE-Independent Extracellular Release of a Mucosal Mast Cell Granule-Specific β-Chymase, Mouse Mast Cell Protease-1

Intestinal mucosal mast cells (IMMC) express granule neutral proteases that are regulated by T-cell–derived cytokines, including interleukin-3 (IL-3) and IL-9, and by stem cell factor (SCF). The IMMC-specific chymase, mouse mast cell protease-1 (mMCP-1), is released in substantial quantities into the blood stream during gastrointestinal allergic responses. We used cultured bone marrow-derived mast cells (mBMMC) to identify cytokines that regulate the expression and extracellular release of mMCP-1. When grown in IL-3–rich WEHI (15% vol/vol) and 50 ng/mL recombinant rat SCF (rrSCF) bone marrow cells supplemented with IL-9 (5 ng/mL) differentiated into mBMMC that expressed a maximum of less than 250 ng mMCP-1/106 cells and 189 ng mMCP-1/mL of culture supernatant. Supplementation of the same three cytokines with transforming growth factor-β1(TGF-β1; 1 ng/mL) resulted in substantially enhanced expression (6 μg/106 mBMMC) and extracellular release (2 μg/mL of culture supernatant) of mMCP-1. The response to TGF-β1 was dose-dependent, with maximal effect at 1 ng/mL, and was associated with immunohistochemical and ultrastructural changes in the secretory granules. IL-9–induced expression of mMCP-1 may be due to endogenously expressed TGF-β1, because it was blocked by anti–TGF-β antibodies. In conclusion, the expression and extracellular release of the IMMC-specific chymase, mMCP-1, is strictly regulated by TGF-β1.

Mucosal mast cell responses and release of mast cell protease-I in infections of mice with Hymenolepis diminuta and H. microstoma: modulation by cyclosporin A

The dynamics of intestinal mucosal mast cells and the major mucosal mast cell protease were followed during the course of laboratory infections of mice with Hymenolepis diminuta and H. microstoma. The effects of the drug cyclosporin A (CsA), which is both immunosuppressive and selectively anthelmintic depending upon dose regime, were determined. In H. diminuta infections worm expulsion occurred around day 9 and coincided with peak mastocytosis and peak mMCP-I concentrations in tissues and serum. Immunosuppressive treatment with CsA prevented worm expulsion, permitting some individuals to reach maturity, and abrogated mast cell proliferation and mMCP-I production and release. By contrast, H. microstoma infections persisted for 64 days in spite of a considerable mastocyosis in both intestine and bile duct tissues accompanied by a high level of mMCP-I in tissues and serum. A subimmunosuppressive regime of CsA had only limited effects on worms and mast cell numbers and activity. Together these data shed light on the variable mast cell response to gastrointestinal infections and on the potential significance of parasite location in evasion of mast cell action. Use of CsA reveals the contributions of both T cell-dependent mechanisms, including mast cell proliferation and activation, and T cell-independent events in regulating intestinal helminth infections.

Histochemical and ultrastructural modification of mucosal mast cell granules in parasitized mice lacking the beta-chymase, mouse mast cell protease-1

The soluble beta-chymases mouse mast cell protease-1 (mMCP-1) and rat mast cell protease-II are predominantly expressed by intestinal mucosal mast cells (IMMCs) and may promote mucosal epithelial permeability when released during intestinal allergic hypersensitivity responses. To study the function of these chymases, we generated mice with a homozygous null mutation of the mMCP-1 gene and investigated their response to infection with the intestinal nematode Nippostrongylus brasiliensis. Whereas mMCP-2, -4, and -5 were transcribed normally, there was no transcription of the mMCP-1 gene in null (-/-) mice, nor was mature mMCP-1 protein detected in (-/-) jejunal mucosa. In contrast, levels of mMCP-1 in wild-type (+/+) jejunal mucosa increased 200- to 350-fold from 0.66 microg mMCP-1/g wet weight in uninfected mice to 129 and 229 microg/g wet weight on days 8 and 10 of infection, respectively. The kinetics of IMMC recruitment differed in -/- mice compared with +/+ controls on days 8 (P < 0.05) and 10 (P < 0.03) of infection. The IMMCs in infected -/- mice stained poorly, if at all, for esterase with naphthol AS-D chloroacetate compared with the intense staining observed in +/+ controls. Ultrastructurally, the prominent crystal intragranular structures that are found in intraepithelial +/+ IMMCs were absent from -/- IMMCs. These data show that disruption of the mMCP-1 gene leads to profound histochemical and ultrastructural changes in IMMC granules.