| The gastrointestinal tract is exposed to countless numbers of microorganisms including bacteria, fungi, yeasts and parasites etc. The normal intestinal microflora has been involved with the process of physiology, biochemistry and pathology, it constitutes an important barrier of immunology, protects the host from the invasion and breeding of pathogen. Antibiotic peptide or protein (AMPs) was secreted by enterocyte and immunocyte, which including mucin, intelectin, lysozyme and defensin etc, shows very strong and important effect on defend the host and maintain the stabilization of internal environment. Autophage is the most important research area in life science recently, it is a progress of cytoplasmic degradation by lysosome in all types of eukaryotic cells, which plays an important role in growth, development and disease process, especially in the accommodation of the natural immunity and adaptive immunity. Recently, people have focused on the alteration of antibiotic peptide expression in the intestine which is infected by bacteria, Too little is known about the alteration of AMPs whether or not it could induce autophage, and alteration of intestinal microflora during the interaction between gut epithelial cells and invaded parasites, such as Trichina spiralis. Therefore, the aim of this study was to investigate the immune response after BALB/c mouse infected by T. spiralis ISS534, including the alteration of cytokine, antibiotic peptide, autophage and microflora etc.6-8 wk BALB/c mice were gavaged with 300 muscle larvae per mouse and killed on day 7 and 14. Jejunum and colon were collected for tissue culture in vitro. Spontaneous IL-10, IL-12, IL-6, IL-17, IFN-γand TNF-αproteins in gut fragment cultures were assayed by ELISA. The result showed that IL-10 secretion was highly increased in jejunal fragments cultures at 14d postinfection (PI) (1375.49±160.62 vs. 20.13±16.86 pg/ml, p<0.01). But low level of IL-6, IL-12 and IL-17 expression was assayed, especially IL-6 secretion was highly decreased at 7d PI (121.35±102.50 pg/mL vs 770.42±99.08 pg/mL, p<0.01). In colon, the expression of IL-6, IL-10 and IL-17 was decreased, among of them IL-10 production was low versus control mice (17.93±3.27 vs 60.17±8.96 pg/mL, p<0.01). But IL-12 secretion was increased to 302.79±29.04 pg/mL, then reduced to the level of control group. The expression of IFN-γand TNF-αwere increased on day 7 and 14. The result showed that IFN-γsecretion was highly increased in colon at 14d postinfection (PI) (≈400 pg/mL, p<0.01). In jejunum, the expression of TNF-αwas highly increased on day 14 (11.41±1.26 pg/mL vs 0.09±0.86 pg/mL, p<0.01). And TNF-αproduction in colon on day 7 was also highly increased versus control mice (8.33±1.31 pg/mL vs 1.04±0.80 pg/mL, p<0.01). The result indicated humoral immunity and cellular immunity were involved with the immunological reaction induced by T. spiralis infection, which provokes Th2 responses in an infected host.AMPs is micromolecule polypeptide, which takes part in the inflammatory reaction, function as barrier in the host defense on the pathogenic microorganism. The small intestine is consisted of enterocyte, goblet cell, enteroendocrine cell and paneth cell. Goblet cell secretes mucin and intelectin, lysozyme and defensin (cryptdin) are secreated by paneth cell. Through the histological observation, the number of goblet cell increased as BALB/c mice were infected by T. spiralis. Intelectin and Mucinl mRNA expression level was elevated by Real-time PCR assay, but mRNA level of Mucin2 was low versus control mice, maybe it is induced by the alteration of function of goblet cell during T. spiralis infection. Increases of lysozyme andβ-defensinl mRNA level was observed, which were secreted by paneth cell, especially marked highβ-defensinl mRNA expression (foldΔ:382.68±0.42, p<0.01) was observed in mouse jejunum at 14d PI versus uninfected mice. It was demonstrated that antibiotic peptide was important for the immune response during T. spiralis infection.The major method for detecting autophage is to observe the ultrastructure by transmission electron microscope (TEM), or measure the autophagosomal structural protein LC3. Swelling of endoplasmic reticulum, eosinophilia was observed in mouse jejunum at 7d PI, the appearance of autophagosome, the number of intermediate cell increased, mitochondrial swelling and eosinophilia at 14d PI. Meanwhile, LC3B protein expression level in jejunum and colon was elevated throughout 7d and 14d PI, and marked high LC3B protein expression was detected by Western blot, it illustrated that autophage also takes part in the immune response after parasitic infection.As a complex and delicately balanced ecosystem, intestinal normal flora associated closely with animal physiological and immune function. To analyze the variation of intestinal microflora in mice with T. spiralis infection by real-time PCR, the genome of murine feces was extracted, and a set of 16S rRNA gene group of species-specific primers for Bifidobacterium spp., Lactobacillus sp., Enterococcus and Fusobacterium spp. were designed, then the plasmid was constructed as control. The result showed that the number of Lactobacillus sp. and Bifidobacterium spp. decreased after infection, and Lactobacillus sp. recoverd as control at 14d PI. The quantity of Enterococcus and Fusobacterium spp. increased, and marked Fusobacterium spp. quantity (2.83×1018 CFU/g, p<0.01) was observed in murine feces at 14d PI versus uninfected mice (7.74×1010 CFU/g). It proved that there was alteration of intestinal flora as T. spiralis infection.In a word, it suggests cytokine, antimicrobial peptides, autophage and intestinal normal flora may involve in mediating host defense to T. spiralis infections, which located in jejunum. The results mentioned above will establish foundation for the mechanism of intestinal immune response of mice infected by T. spiralis.
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