Morphological, phenotypic and functional characteristics of a pure population of CD56+ CD16- CD3- large granular lymphocytes generated from human duodenal mucosa

Interleukin-2 (IL-2)-dependent large granular lymphocytes (LGL) with a distinctive surface phenotype were generated from histologically normal duodenal biopsy tissues. Immunoperoxidase staining of the mucosa with an anti-CD56 monoclonal antibody revealed LGL localized in the lamina propria rather than in the epithelium. Light and electron microscopy demonstrated azurophilic and electron-dense cytoplasmic granules. Flow cytometry analysis revealed that these cells express CD45, CD56, CD2, CD7, CD11a, CD18, CD69 and the intermediate affinity (p70) IL-2 receptor (IL-2R) but not CD57, CD16, CD3, CD4, CD5, CD8, CD45RA, CD25, or the high affinity p55 IL-2R. The LGL proliferated when cultured in the presence of human rIL-2 but not in the presence of human rIL-4. Functional studies demonstrated that the LGL had strong cytotoxicity against natural killer (NK) target cells, K562, but not NK-resistant targets such as Colo 205, Melanoma and Epstein-Barr virus (EBV)-transformed B-cell lines. The LGL expressed genes for IL-5, IL-8, granulocyte-macrophage colony-stimulating factor (GM-CSF) and tumour necrosis factor-alpha (TNF-alpha) and the corresponding cytokines were detected in culture supernatant. These results provide evidence for an important role of gut mucosal LGL in the induction and regulation of inflammation and immunity in the gut.

Adaptation of the small intestine in desert-dwelling animals: morphology, ultrastructure and electrolyte transport in the jejunum of rabbits, rats, gerbils and sand rats

1. The aim of this study was to characterize adaptive alterations of the small intestine in desert-dwelling animals by comparing jejunal morphology, ultrastructure and function in mammalian species with or without desert habitat origins. 2. Crypt-villus architecture, brush border surface area, and electrolyte transport were measured and compared in the jejunum of rabbits (Oryctolagus cuniculus), rats (Rattus rattus), gerbils (Meriones unguiculatus) and sand rats (Psammomys obesus). 3. In addition, transport of 3-0-methyl-D-glucose was compared in rats, rabbits and gerbils. 4. Gerbils and sand rats had significantly longer microvilli and villi (P < 0.01), increased brush border surface area (P < 0.01), and greater absorption of Na+ and Cl- (P < 0.05) than rabbits and rats. 5. Absorption of 3-0-methyl-D-glucose was also significantly (P < 0.05) greater in gerbils than in rabbits or rats. 6. The findings demonstrate enhanced small intestinal absorption of electrolytes and nutrients in desert-dwelling animals. 7. This increase was associated with an enlarged mucosal absorptive surface area. 8. The findings suggest that intestinal mucosal adaptation allows desert-dwelling animals to compensate for the limited availability of water and nutrients in an arid environment.

The effect of enterohemorrhagic Escherichia coli O157:H7 on intestinal structure and solute transport in rabbits

BACKGROUND

The effect of enterohemorrhagic Escherichia coli O157:H7 infection on intestinal morphology and solute transport was examined.

METHODS

New Zealand white rabbits, aged 10 days, were infected with E. coli strain EDL933 (O157:H7 containing the 60-megadalton plasmid-encoding adhesion factors VT1 and VT2) and compared with controls. Small and large intestinal histology and solute transport were studied 5 days after inoculation. Ion transport in the distal colon was also examined in animals infected with different strains encoding a combination of pathogenic factors.

RESULTS

Infection with EDL933 induced diarrhea and mucosal disease in the colon, inhibited colonic Na+ absorption, and stimulated of Cl- secretion, but had no impact on the small intestine. Infection with strains A7785-C3A (O157:H7, plasmid-, VT1+, VT2+) and 85-170 (O157:H7, plasmid+, VT-) induced similar transport changes to EDL933. C600/1 (E. coli K-12, plasmid+, VT1+) decreased Na+ and Cl- absorption only.

CONCLUSIONS

Abnormalities of colonic structure and ion transport could account for diarrhea production, but pathogenic factors other than the 60-megadalton plasmid-encoding adhesion factor and verotoxins appear to be involved in enterohemorrhagic E. coli infection.

Effector mechanisms of intestinally induced immunity to Pseudomonas aeruginosa in the rat lung: role of neutrophils and leukotriene B4

This paper investigates the effector mechanisms of immune clearance in the lungs of rats immunized against mucoid Pseudomonas aeruginosa. After the gut-associated lymphoid tissue was primed and after a subsequent pulmonary challenge with live bacteria, significantly accelerated bacterial clearances from the lung and raised levels of anti-P. aeruginosa antibodies in sera (immunoglobulin G [IgG], IgA, and IgM) and bronchoalveolar lavages (IgG and IgA) were observed for all immune animals. These changes were associated with enhanced recruitment, chemotaxis, chemokinesis, phagocytic indices, and chemiluminescence of pulmonary polymorphonuclear neutrophils (PMN). In the alveolar spaces of immune animals, an increase in the level of PMN recruitment was not associated with higher levels of leukotriene B4 (LTB4). In contrast, in nonimmune animals that were intratracheally infected with P. aeruginosa, the levels of recruitment and activity of alveolar PMN were lower than those in immune rats but PMN infiltration correlated with a significant increase in the synthesis of LTB4 in the alveolar space. In pulmonary tissue, LTB4 synthesis for both groups was elevated. These findings suggest that accelerated clearance of mucoid P. aeruginosa from the lungs of intestinally immunized rats is due at least in part to factors that induce the enhancement of PMN recruitment and activity in the alveolar space. The mediators that regulate this enhanced response remain unknown but do not seem to include LTB4. The high levels of LTB4 measured in the bronchoalveolar lavages and pulmonary tissues from nonimmune animals infected with live bacteria implicate LTB4 as an important amplifier of the inflammatory response during acute pulmonary infections with mucoid P. aeruginosa in unimmunized hosts.

Effect of epidermal growth factor on enterocyte brush-border surface area

The effect of acute in vivo epidermal growth factor (EGF) exposure on intestinal absorptive surface area was examined in blind jejunal loops in New Zealand White rabbits (500-900 g). Brush-border surface area was assessed by electron microscopy at 30 and 120 min, and total surface area was assessed by the fluorophore 1-[4-(trimethylamino)phenyl)]-6-phenylhexatriene (TMA-DPH) at 10 and 60 min after EGF exposure. Mucosa obtained at 120 min was also used for morphometrics and analysis of membrane composition and fluidity. Brush-border surface area was significantly increased in EGF-treated tissue after 30 (42%) and 120 min (60%). Total absorptive surface area measured by TMA-DPH was increased more than twofold after 10 and 60 min EGF exposure. The increase in absorptive surface area was abolished by pretreatment with intravenous verapamil. Mucosal morphometrics and membrane sucrase activity, total phospholipids, cholesterol content, cholesterol-to-phospholipid ratio, phospholipid species (wt%), phospholipid fatty acid composition, and fluidity did not differ between control and EGF-treated tissue. These findings indicate that EGF can rapidly increase brush-border surface area by a mechanism that appears to be due to a redistribution of existing performed microvillus plasma membrane.

Pathophysiology of small intestinal malabsorption in gerbils infected with Giardia lamblia

Mongolian gerbils were infected with a human pathogenic Giardia lamblia strain and compared with sham-treated control animals 6 days after inoculation. Infection resulted in crypt hyperplasia associated with an increased enterocyte migration rate. Villus height was decreased in the duodenum, unchanged in the jejunum, and increased in the ileum of infected animals. Epithelial microvilli were markedly shortened, and brush border surface area decreased in the jejunum and ileum of infected animals. Thymidine kinase activity was increased in isolated duodenal villus enterocytes but did not differ in the jejunum and ileum. In vitro and in vivo experiments showed that the infection resulted in decreased jejunal glucose-stimulated electrolyte, water, and 3-O-methyl-D-glucose absorption, whereas in the ileum in vitro electrolyte and 3-O-methyl-D-glucose absorption was similar in infected and control animals. Thus, in the jejunum infection causes electrolyte, solute, and fluid malabsorption associated with decreased brush border surface area. The results indicate that the diarrhea associated with giardiasis is caused by malabsorption rather than active secretion.

Effects of Yersinia enterocolitica infection on rabbit intestinal and colonic goblet cells and mucin: morphometrics, histochemistry, and biochemistry

The effects of Yersinia enterocolitica on intestinal goblet cells were investigated in New Zealand white rabbits. Animals infected with Y enterocolitica were compared with weight matched and pair fed controls. Goblet cell hyperplasia developed in the distal small intestine of infected rabbits on day 1, in the mid small intestine on day 3, and in the upper small intestine on day 6. In all regions hyperplasia persisted throughout the 14 day study. The degree of hyperplasia was greater in the distal small intestine than the upper and mid regions. Goblet cells in the proximal colon of infected animals seemed to respond as those in the distal small intestine. Thus goblet cell hyperplasia developed more rapidly and to a greater extent in the ileocaecal region where mucosal injury was most severe. These changes resulted directly from Y enterocolitica infection since goblet cell numbers did not increase in pair fed controls. Histochemically, goblet cell mucins from infected rabbits were unchanged at either six or 14 days. Biochemical analysis, however, established that purified mucins from animals on day 6 after infection were less sialylated (in the small intestine) and more sulphated (in the small intestine and proximal colon). In addition, mucins from the distal small intestine and the proximal colon seemed to contain fewer but longer oligosaccharide chains.

An in vivo model to study the pathobiology of infectious biofilms on biomaterial surfaces

This study examines the morphology, ultrastructure, and microbiology of the intact biofilm developing on an implant surface. Silastic subdermal implant material was colonized with P. aeruginosa and surgically inserted into the peritoneal cavity of adult rabbits. After 4, 8, 28, and 42 days implants were recovered and the intact biofilms examined. P. aeruginosa colonized the implant throughout the entire experimental time. Microcolonies of glycocalyx-coated bacteria were observed within the biofilm. However, the bulk of the biofilm was host-generated and typically contained phagocytes trapped within a thick mesh of fibrin. Polymorphonuclear neutrophils were the predominant cell type. Isolated erythrocytes, macrophages, and fibroblasts were also observed. By day 28, the biofilm was enclosed in a fibrous capsule of vascularized connective tissue. The low numbers of neutrophils seen in biofilms from sterile Silastic sheets implanted into control animals suggested that neutrophilia may represent a specific cellular response to the bacterial colonization. The results indicate that the cell-mediated immune response provides for most of the biofilm mass on colonized implant surfaces. Inactivated phagocytes trapped in fibrin may "wall-off" the embedded bacterial microcolonies and thus shield them from live phagocytic leucocytes. Such a mechanism may play an important role in the pathogenesis of prosthetic device infections.

Axenic isolation of viable Giardia muris trophozoites

Large numbers of viable Giardia muris trophozoites were isolated from the duodenum of experimentally infected mice 6 days after inoculation with 1,000 G. muris cysts. A series of shaking, incubation, and washing steps in the presence of the broad-spectrum antibiotic piperacillin readily provided 4.9 +/- 1.5 x 10(5) G. muris trophozoites per mouse, free of detectable contaminant organisms. Anaerobic and microaerophilic culturing and scanning electron microscopy demonstrated axenic status and high purity of the isolates. The viability of trophozoites was 98 +/- 2%. Application of this technique should permit novel immunological and epidemiological analyses of G. muris infection and biochemical investigations of this protozoan parasite.

Growth, activities of enzymes in the small intestine, and ultrastructure of microvillous border in gerbils infected with Giardia duodenalis

The aim of this study was to assess and correlate changes in weight gain, food intake, small intestinal disaccharidase activities and microvillous border surface area over the course of a primary Giardia duodenalis infection in weanling Mongolian gerbils (Meriones unguiculatus). Weight gain in infected animals was significantly impaired between days 8 and 20 postinoculation when compared to age- and weight-matched controls. No difference in food intake was observed between groups. Trophozoite population in the small intestine was maximal on day 4 and 6 of infection, and colonization persisted in the duodenum throughout the experiment (30 days). In infected gerbils, mucosal sucrase and maltase activities were significantly depressed in the duodenum and jejunum on day 4 and in all areas of the small intestine by day 6. Eight and 25 days postinoculation, disaccharidase activities had recovered in the jejunum and distal small intestine but remained depressed in the duodenum, the area where trophozoite colonization persisted. Diffuse loss of microvillous border surface area was observed in the duodenum and jejunum after 6 days of infection. Eight days postinoculation, microvillus surface area had returned to normal in the jejunum, but not in the duodenum. Our findings demonstrate that acute giardiasis in weanling gerbils impairs weight gain, depresses disaccharidase activities, and diffusely reduces mucosal microvillous border surface area.(ABSTRACT TRUNCATED AT 250 WORDS)

Intestinal protozoa and epithelial cell kinetics, structure and function

Intestinal protozoa are not only common enteric pathogens in the tropics but also the high incidence of infection among immunocompromised patients in northern countries has evoked an increased interest in these parasites. Although enteric protozoa are a major cause of diarrhea and malabsorption in humans and other animals, the pathophysiology of gut disturbances caused by them remains poorly understood. Clinical signs related to enteric protozoan disease commonly involve malabsorption, diarrhea, weight loss or retarded weight gain and anorexua. Since these infections are most prevalent and most severe in the young, this may translate into considerable illness among children and significant loss to the agricultural economy where domestic animals are prone to infection. In this review we describe the effects of intestinal protozoan diseases on the structure, kinetics and function of absorptive intestinal cells and other epithelial cells, and correlate morphological injury with physiological alterations in the parasitized gut. Some of the interactions between immune responses and pathophysiology will be discussed, but in-depth discussion of intestinal immunity has recently been undertaken by other authors.

Zoonotic potential of giardiasis in domestic ruminants

This study was conducted to assess the prevalence and zoonotic potential of giardiasis in domestic ruminants. Prevalence of infection was 17.7% in sheep and 10.4% in cattle and was significantly higher in lambs and calves (35.6% and 27.7%, respectively). Naturally infected lambs released cysts intermittently for months. Giardia trophozoites from sheep had typical claw hammer-shaped median bodies and were successfully cultured in TYI-S-33 medium, and cytosolic, cytoskeletal, and membrane fractions exhibited protein profiles similar to human isolates (WB). Immunoblotting showed that sera from infected sheep recognized human Giardia, sera from patients with giardiasis recognized Giardia from sheep, and in both cases recognition involved antigenic proteins of similar molecular weight. Cyst output and clinical signs in ovine infection resemble human disease and the organisms infecting humans and ruminants are morphologically and antigenically similar. It is postulated that domestic ruminants may be a reservoir for human infection and vice versa, thus classifying giardiasis as a zooanthroponotic disease.

Effect of acute Yersinia enterocolitica infection on small intestinal ultrastructure

The purpose of this study was to assess the jejunal and ileal brush border injury caused by Yersinia enterocolitica and to correlate these alterations with functional abnormalities. Weanling rabbits infected with 10(10) organisms of a human pathogenic Y. enterocolitica strain were compared with control and pair-fed, sham-treated animals. On day 6, infection resulted in a diffuse decrease in brush border enzyme activities in the small intestine and villus atrophy and crypt hyperplasia in the ileum. By day 14, ileal architecture and jejunal disaccharidases had returned to normal, but enzyme abnormalities persisted in the ileum. Ultrastructural studies showed decreased brush border surface area in the jejunum and ileum on day 6 and in the ileum on day 14 of infection. Abnormalities of brush border function caused by infection correlated with the changes in microvillus surface area. In pair-fed animals on day 6, brush border surface area was slightly decreased in the ileum but increased in the jejunum, suggesting that the brush border injury resulted from infection rather than from malnutrition alone. The findings indicate that Y. enterocolitica inflicts a diffuse brush border injury that is in keeping with the generalized defect in brush border enzyme activity and transport function.

Effects of murine giardiasis on growth, intestinal morphology , and disaccharidase activity

The aim of this study was to assess the effects of Giardia muris on host growth and food intake, small intestinal morphometrics, mucosal enzyme activities, and brush border ultrastructure. Weanling mice infected with 1,000 G. muris cysts were compared to control and pair-fed sham-treated animals. Infection with G. muris resulted in decreased food intake and retarded growth. In infected animals, villus atrophy was observed in the duodenum throughout the study period and in the jejunum on days 8 and 50. On day 30, whereas jejunal architecture returned to normal in infected animals, malnourished pair-fed animals exhibited a compensatory increase in villus height. Sucrase and maltase were depressed in infected animals on days 2-24. On day 8 jejunal disaccharidases in pair-fed animals were also decreased but to a lesser extent than in infected animals. On day 24, disaccharidase values for control and infected mice were similar, whereas values in pair-fed animals were increased. On day 8, jejunal microvilli were shorter in infected animals than in control and pair-fed animals. This brush border injury was present throughout the jejunum and was also observed in pair-fed animals, but to a lesser extent. These findings suggest that G. muris retards growth in weanling mice, results in small intestinal injury, and interferes with the compensatory response to malnutrition of the infected host. Villus atrophy and brush border enzyme deficiencies associated with the disease mainly occur in the duodenum and jejunum, where trophozoites are most numerous. In infected and in pair-fed animals, the decrease in jejunal disaccharidase activities correlated with a diffuse shortening of brush border microvilli.

Intestinal anaphylaxis: in vivo and in vitro studies of the rat proximal colon

The response of the rat proximal colon to an immunoglobulin E (IgE)-mediated hypersensitivity reaction was examined. Rats were sensitized to egg albumin (EA) by intraperitoneal injection, and serum titers of specific anti-EA IgE were measured at 14 days. Sensitized animals had titers of greater than or equal to 1:64, whereas no anti-EA IgE antibodies were detected in controls. Water and electrolyte absorption in the proximal colon, before and during antigen challenge, was measured by in vivo marker perfusion. Antigen challenge resulted in significant inhibition of water, Na+, Cl-, and K+ absorption in vivo. Proximal colonic tissue from sensitized and control animals was studied in Ussing chambers under short-circuited conditions. Antigen challenge of sensitized tissue resulted in significant increases in short-circuit current due to the induction of active Cl- secretion. No such changes were seen in control tissue. The abnormalities induced by antigen challenge in tissue from sensitized animals was blocked by doxantrazole (10(-3) M), a mast cell stabilizer. The findings indicate that IgE-mediated reactions in rat proximal colon to a food protein cause pertubations in water and electrolyte transport secondary to active Cl- secretion and these abnormalities appear to be due to mast cell degranulation.

Mast cell protease release and mucosal ultrastructure during intestinal anaphylaxis in the rat

Intestinal anaphylaxis is associated with disturbances in gut function that are antigen-specific and dependent on mast cell degranulation. Using an animal model of intestinal anaphylaxis, we have correlated alterations in water and electrolyte transport, associated with intraluminal challenge, with specific intestinal mucosal mast cell degranulation by following systemic as well as local release of rat mast cell protease II. This protease is specific for intestinal mucosal mast cells and is known to selectively attack type IV collagen, which is found in basement membranes. Intraluminal antigen challenge in sensitized animals dramatically increased serum and intraluminal levels of rat mast cell protease II. Serum levels continued to rise throughout the duration of antigen challenge. Although light microscopy of challenged intestine demonstrated little distortion of mucosal architecture, ultrastructural examination revealed significant disruption to the basement membrane and underlying collagenous matrix of the intestinal mucosa. Our findings indicate that during mucosal immunoglobulin E-mediated reactions, rat mast cell protease II is released and is associated with ultrastructural changes in the intestinal mucosa. The systemic appearance of this specific protease provides a serum marker of intestinal anaphylaxis.