Maya Eran

Are Intraepithelial Lymphocytes in Celiac Mucosa Responsible for Inducing Programmed Cell Death (Apoptosis) in Enterocytes? Histochemical Demonstration of Perforins in Cytoplasmic Granules of Intraepithelial Lymphocytes

BACKGROUND Programmed cell death refers to the genetically determined processes by which cells die in response to physiologic extracellular and intracellular signals, morphologically described as apoptosis. In physiologic and pathologic circumstances this process may involve effector and target cells. METHODS To identify serine esterase granules in intraepithelial lymphocytes, fresh-frozen human small intestine mucosal sections from normal and celiac-affected mucosa were incubated with substrate-specific N-alpha-benzyloxy-carbonyl-L-lysine thiobenzyl (BLT) and a chromogen (4 Benzoylamino-2,5-diethoxybenzene-dazonium chloride hemi [zinc chloride] salt as capture agent and were examined by light microscopy. RESULTS Normal mucosa showed an occasional intraepithelial lymphocyte with BLT-positive intracytoplasmic granules. Some large mononuclear cells of the lamina propria were similarly stained. Many more intraepithelial lymphocytes were BLT-positive among the surface enterocytes of untreated celiac mucosa. Lamina propria mononuclear cells close to the basal layer of crypt cells also appeared to be increased. CONCLUSIONS The histochemical identification of BLT-positive esters within intraepithelial lymphocytes suggests their involvement in enterocyte death under physiologic conditions. The increased BLT-positive intraepithelial lymphocytes found in the celiac mucosa may be related to the known increase in cytotoxic intraepithelial lymphocytes in untreated celiac disease.

The Effect of Immediate-Type Gastrointestinal Allergic Reactions on Brush Border Enzymes and Gut Morphology in the Rat

ABSTRACT: The aim of the present study was to create clearly documented immediate-type allergy to food protein in the intestine of rats and to study some pathophysiological phenomena induced by challenge with the allergen. To achieve this, rats were sensitized with ovalbumin. A passive cutaneous anaphylaxis reaction to ovalbumin was negative in all controls and positive in all test animals when Bordetella pertussis was used as adjuvant. Sixty minutes after an intravenous injection of 125I-human serum albumin and 45 min after an ovalbumin challenge, given by gavage, the rats were sacrificed. The intestine was removed and sections taken for morphologic studies. The remainder was rinsed, opened, cut into measured segments, weighed, and the radioactivity was measured. Disaccharidases, alkaline phosphatase, and protein were estimated in homogenates of epithelium. Results in both control and test animals showed that radioactivity decreased as one moved distally along the intestine. However, radioactivity was significantly higher (p < 0.01) in the intestine of test animals than in controls. Radioactivity in liver, kidney, spleen, and lungs was identical in test and control animals. There was significant reduction in levels of alkaline phosphatase (p varied from < 0.05 to < 0.001), maltase (p < 0.05), and sucrase (p < 0.05 to < 0.01). Lactase activity in contrast was significantly raised (p < 0.05). There was no change in intestinal morphology or in the intestinal mast cell count.

Relative expression and localization of the insulin-like growth factor system components in the fetal, child and adult intestine.

Background: The insulin-like growth factors (IGFs) are important in the development and maintenance of the gastrointestinal tract. Objectives: To compare the expression of IGFs and their receptors in the stomach and duodenum of the fetus, the child and the adult. To identify the cells mainly responsible for the production of the members of the IGF system. Methods: Tissue was obtained from fetus after abortion and from children and adults during diagnostic endoscopy and biopsy. The expression of the IGFs and their receptors was estimated by an RNAse protection assay and sections were stained with antisera to the components of IGF system. Results: The tissues from the stomach and the duodenum expressed the two IGFs and their receptors at all stages of life. The fetal IGF receptors I and II, were approximately ten times higher than in the child and IGF-II was five times higher. Immunohistochemical staining showed the components of the IGF system to be localized to the gastric glands and to the basotlateral border of the gastric epithelial cells. In the duodenum, they were concentrated at the apical portion of the epithelial tissue. They could also be identified in ganglion cells and nerves. Conclusions: The IGFs and their receptors in the stomach and duodenum are expressed in all age groups and mostly are highest in the fetus. The IGF system proteins were located in the gastric glands and epithelium and in the apical portion of the villous epithelium of the duodenum.

Substance P Accelerates Secretory Component-Mediated Transcytosis of IgA in the Rat Intestine

We have previously shown that cholecystokinin (CCK) causes secretion of specific IgA antibodies in the rat intestine.1 The objective of the experiments described below was to establish if another gut-brain peptide, substance P (SP), also accelerates secretion of IgA. The reason for choosing this peptide was that SP is functionally similar to CCK, though chemically quite unrelated. Once having established that SP, indeed, causes secretion of IgA specific antibodies, we proceeded to obtain data on the molecular size of the IgA, on its probable mode of transport and on the absolute amounts secreted.

Rise of Prostanoids in Rat Small Intestinal Mucosa following Intestinal Protein Hypersensitivity

ABSTRACT.: The purpose of the present study was to establish whether there is an elevated prostaglandin concentration in the intestinal mucosa in rats suffering from an immediate type hypersensitivity reaction. Rats of the Hooded-Lister strain were sensitized and challenged with ovalbumin. Control rats were given adjuvant only. Prostanoid content of scraped mucosa was determined by radioimmunoassay. It was found that the prostaglandin E2 content in the sensitized intestine was significantly elevated as compared to the controls. There was no significant rise of 6-keto prostaglandin Fα or thromboxane E2 in the sensitized rats. These results show that prostaglandin B2 participates in intestinal immediate type responses and may explain some of the clinical manifestations of food protein allergy.

Cholecystokinin-octapeptide (CCK-OP) and substance P (SP) influence immune response to cholera toxin in live animals.

The immune response in the intestine is initiated by antigen uptake at the level of Peyer’s patches (PP)1 and along the small intestine.2,3 A series of initiating and enhancing signals are required to effect T cell activation by polypeptide antigens. A degree of antigen processing by the antigen-presenting cell (APC) to reveal epitopes reactive with the T cell receptor is usually required.4 Interaction of the processed antigen with the T cell receptor is regulated by products of the major histocompatibility complex residing in the APC surface membrane.5 Release by the APC of the cytokine IL-1 is required to induce the synthesis of receptors for IL-2 on the T cell.6 These processes regulate the subsequent production of specific antibodies by B cells. It may be desirable, in certain circumstances, to enhance the immune response. An obvious example is the administration of oral vaccines. On the other hand, there may be occasions when it is desired to abrogate the immune response, for instance, in order to prevent hypersensitivity responses. One method of enhancing the immune response in the intestine is by the concomitant administration of the antigen with an appropriate adjuvant. In this report, we wish to investigate the potential adjuvant effect of some peptide hormones in regulating the immune response to foreign antigens in the intestine. We chose the peptide hormones, substance P (SP) and cholecystokinin- octapeptide (CCK-OP) as well as their respective antagonists, spantide and L 316,718. In addition, we investigated the effect of capsaicin, which is a toxin to SP containing-nerve fibers.

28. IS IMMUNOGLOBULIN ‘A’ (IgA) RELEASE IN THE INTESTINE CONTROLLED BY A CALCIUM DEPENDENT SECRETORY MECHANISM?

It has previously been shown that cholecystokinin octapeptide (CCK-8)as well as pilocarpine can accelerate the release of IgA in the gastrointestinal tract. The purpose of this study was to ascertain if CCK-8-induced IgA release involves calcium-coupled secretory mechanisms in the intestine. Hooded Lister rats were immunized with ovalbumin and Freunds complete adjuvant and a booster injection given 14 days later. On the 21st day a 10 cm. long segment of intestine was isolated 10 cm. distal to the pylorus. This was perfused with saline 0.5 ml/2.5minutes. After a flush out period of 30 mins. aliquots were collected every 2.5 mins. After 10 minutes 1 u CCK was given I.V.(group 1). A second group of animals received a calcium channel blocker Verapramil I.V. at a rate of 2 mcg/min. for 20 minutes. After the first 10 mins. 20 ng CCk-8 were administered I.V. Group 3 was given Verapramil only as above.Results: following CCK-8 there was a significant rise of IgA into the intestinal fluid which began at 2.5 minutes and persisted for 10 minutes. Prior administration of Verapramil completely inhibited the CCK-8-induced release of IgA. Conclusion: it is suggested that CCK-8-induced release of IgA into the gastrointestinal tract is related to calcium dependent secretory mechanisms.

73. LEUKOTRIENE B4 (LTB4) CONTENT OF SMALL INTESTINAL MUCOSA IN RAT MODEL OF PREOTEIN HYPERSENSITIVITY

Both prostanoids and leukotrienes are metabolic products of arachidonate via separate enzymatic pathways. We have previously shown that prostaglandin E2 content in small intestinal mucosa from ovalbumin (OA) sensitized rats is elevated as compared to controls. The purpose of this investigation was to establish whether there is an elevated LTB4 content in the intestinal mucosa in rats suffering from an immediate type gastrointestinal allergic reaction. 8 rats of the Hooded-Lister strain were sensitized with 250 μg OA IP together with B. Pertussis adjuvant. On the 14th day a booster of 2.5 μg OA was given IP. 8 control rats were given adjuvant only. 5 days after the booster the test and control rats were challenged with 25 mg OA intragastrically and 45 minutes later the rats were sacrificed and 5 cm of proximal small intestine removed. LTB4 content of scraped mucosa was determined by radioimmnunoassay. It was found that the LTB4 content in the sensitized intestine was 50±9 pg/mg tissue as compared to a level of 38.7±8.8 pg/mg tissue in controls. This difference was significant (p< 0.025). We conclude that LTB4 may participate in intestinal immediate type responses and may explain some of the clinical manifestations of food protein allergy.

PROSTANOID CONTENT OF SMALL INTESTINAL MUCOSA IN RAT MODEL OF PROTEIN HYPERSENSITIVITY

The purpose of this investigation was to establish whether there is an elevated prostanoid content in the intestinal mucosa in rats suffering from an immediate type gastrointestinal allergic reaction. Ten rats of the Hooded-Lister strain were sensitized with 250 μg/0.5 ml ovalbumin(OA) intraperitoneally (i.p.) together with B. Pertussis adjuvant. On the 14th day a booster of 2.5 μg OA/0.5 ml was given i.p. This procedure has previously been shown by us to produce local intestinal hypersensitivity. Control rats were given adjuvant only. The challenge procedure was identical in test and controls. Five days after the booster the rats were challenged with OA. Twenty-five mg. OA was introduced intragastrically and 45 minutes later the rats were sacrificed and 5 cm. of proximal small intestine removed. Prostanoid content of scraped mucosa was determined by radioimmunoassay. It was found that the PGE2 content in the sensitized intestine was 691±310 pg/mg protein as compared to a level of 424±155 pg/mg protein in controls This difference was significant (p < 0.05). There was no significant rise of 6-Keto PGF1α or TXB2 in the sensitized rats. These results show that PGE2 participates in intestinal immediate type responses and may explain some of the clinical manifestations of food protein allergy.