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T T MacDonald

Publications and source records attributed to T T MacDonald.

At least 109 records · Page 6Linked to original sources
PubMed1994

Ontogeny of the gut-associated lymphoid system in man.

Immunoperoxidase histochemistry using monoclonal antibodies to lymphoid/myeloid cells has been used to study the development of the human mucosal immune system in frozen sections of foetal human intestine at different ages. A steady progression of development was seen between 11 and 19 weeks' gestation. At 11 weeks, Peyer's patches were identifiable only as aggregates of strongly HLA-DR+ cells. By 16 weeks these aggregates became colonized with T and B cells, without distinct cellular zonation. By 19 weeks primary B-cell follicles were seen and T cells occupied the inter-follicular zones. There was also a steady increase in the numbers of lamina propria and epithelial T cells between 11 and 19 weeks' gestation. As in postnatal bowel, CD8+ cells predominated in the epithelium and CD4+ cells predominated in the lamina propria. Thus the important T- and B-cell compartments of the mucosal immune system are well established in the human foetal intestine by mid-gestation.

Fetus↗
PubMed1994

Cyclosporin as initial treatment for Crohn's disease.

Childhood Crohn's disease may cause significant morbidity. T cell activation is considered to be central to Crohn's disease pathology, and as cyclosporin is a powerful inhibitor of T cell activation, and has been used in adult Crohn's disease with encouraging results, it may offer the prospect of remission if given early in the course of disease. Children with newly diagnosed Crohn's disease or those relapsing off treatment were therefore given cyclosporin or conventional treatment (enteral nutrition or corticosteroids) by random allocation. Evaluation was performed initially and at two months. Twenty four children were studied (10 on cyclosporin and 14 on conventional treatment; one child on cyclosporin withdrew). Significant clinical improvement occurred in the group on conventional treatment, but not in the cyclosporin group. Colonoscopic improvement was noted in 5/9 on cyclosporin and 8/14 on conventional treatment, but neither group produced a significant fall in median colonoscopic index. Histological improvement was seen in 7/8 on cyclosporin and 8/13 on conventional treatment, but cyclosporin was not significantly better. Cyclosporin produced improved clinical and histological appearance without matched improvement in blood disease indices. It was not better than conventional treatment, and simple oral administration is probably not suitable for newly diagnosed patients with Crohn's disease.

Adolescent↗
PubMed1994

Decreased mucosal interleukin-4 (IL-4) production in gut inflammation.

AIMS: To determine the prevalence of cells secreting interleukin-4 (IL-4) in the gut mucosa of children with chronic inflammatory bowel disease. METHODS: Mononuclear cells were isolated from intestinal biopsy specimens from control children (n = 10) and children with active inflammatory bowel disease (Crohn's disease n = 15, ulcerative colitis n = 9, indeterminate colitis n = 3). Spontaneous IL-4 production was then measured by SPOT-enzyme linked immunosorbant assay (ELISA) using a pair of non-competing anti-IL-4 monoclonal antibodies. The percentage of T cells in the isolated cells were also determined and the prevalence of IL-4 secreting cells calculated per 10,000 T cells. RESULTS: In control children the mean number of IL-4 secreting cells was 15.1 per 10,000 T cells. In Crohn's disease and ulcerative colitis the means were 5.3 and 5.2, respectively. In two children with indeterminate colitis numbers were also low. There was no difference in the percentage of T cells in the cell preparations isolated from each patient group. The reduction of IL-4 secreting cells in patients with Crohn's disease was not caused by steroids. CONCLUSIONS: In idiopathic inflammatory bowel disease IL-4 secreting cells are reduced in diseased mucosa.

Adolescent↗
PubMed1994

HIV infection of human fetal intestinal explant cultures induces epithelial cell proliferation.

OBJECTIVE: The concept that HIV infection per se alters small intestinal mucosal structure and function (HIV enteropathy) remains controversial and in this study we report in vitro experiments designed to elucidate the matter. METHODS: Twenty pairs of human fetal intestinal tissue explants were maintained in vitro for up to 14 days; one explant of each pair was incubated and infected with HIV, and the other served as a matched uninfected control. At various times after infection, explant culture fluid and tissue were removed, p24 concentration was measured and tissue formalin fixed. Explant tissue was embedded in paraffin wax and sections stained by an immunoperoxidase method directed against proliferating cell nuclear antigen (PCNA). The percentage of proliferating crypt and villous epithelial cells, stained by PCNA, was calculated in paired samples. The difference between the percentage for paired samples was designated delta crypt proliferation (delta CP) and delta villous proliferation (delta VP), respectively. Epithelial cell proliferation was deemed to be enhanced if the percentage of PCNA-stained cells was greater in the HIV-infected than in the control tissue. RESULTS: Explant culture fluid from tissue exposed to HIV showed a progressive rise in p24 antigen (Ag) level, indicating HIV infection of these explants. Fifteen pairs of explants showed progressively positive delta CP with time (P < 0.01) indicating crypt hyperplasia and all 20 pairs of explants showed positive delta VP, indicating hyperplasia of villous epithelial cells. CONCLUSIONS: This study provides direct evidence that HIV stimulates epithelial cell proliferation in intestinal mucosa. HIV-infected human intestinal explants provide a model of crypt hyperplastic villous atrophy previously described as HIV enteropathy and detected in clinical biopsy specimens from HIV-infected patients.

Atrophy↗
PubMed1994

Immune mechanisms in chronic inflammatory bowel disease.

Crohn's disease and ulcerative colitis are chronic inflammatory bowel diseases of unknown etiology. However, there is circumstantial evidence that immune mechanisms play an important role in the pathogenesis of the intestinal lesion, and cytokines produced by lymphoid cells may be critical for the extraintestinal sequelae of the disease. In both Crohn's disease and ulcerative colitis, activation of macrophages seems to be a key feature. Increased production of the macrophage derived cytokines TNF-alpha, IL-1 and IL-6 have been reported in both diseases. Additionally in Crohn's disease, large numbers of activated T lymphocytes can be detected in the lamina propria and the T lymphocyte derived cytokines IL-2 and IFN-gamma are secreted by a higher number of lamina propria T lymphocytes in active Crohn's disease. However, this is not the case in ulcerative colitis. The increased number of activated T lymphocytes secreting IFN-gamma may be responsible for granuloma formation in Crohn's disease, as well as for MHC class II antigen expression on colonic epithelial cells. Lamina propria T lymphocytes seem to have lost their physiological unresponsiveness to several microbial antigens. All these observations suggest that Crohn's disease may be caused by hyperreaction of the local cellular immune system to numerous microbial and nutritional antigens normally present in the intestine. The factor inducing this immune dysregulation remains unknown. Cell-mediated immunity seems to be less important in ulcerative colitis, as activated T lymphocytes are only sparse within the inflamed mucosa, and the T lymphocyte derived cytokines IL-2 and IFN-gamma cannot be detected in the gut lesion or in the serum.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibody Formation↗
PubMed1993

Disruption of sulphated glycosaminoglycans in intestinal inflammation.

We have studied the distribution and nature of sulphated glycosaminoglycans (GAGs) within normal and inflamed intestine. There is increasing evidence that these negatively charged polysaccharides, which both regulate the ability of albumin to leave the vasculature and inhibit thrombosis, may be affected by inflammatory cells and their products. We obtained samples of freshly resected intestinal tissue from eight controls, eleven patients with Crohn's disease, and six with ulcerative colitis. Sulphated GAGs were detected by means of a gold-conjugated poly-L-lysine probe, and the tissue density of anionic sites was assessed semiquantitatively by means of a Lennox graticule. In normal intestine there was staining in the vascular endothelium and the subepithelial basal lamina and throughout the extracellular matrix of the lamina propria and submucosa. Tissue from the patients with inflammatory bowel disease showed inflammation macroscopically and on histology. There were profound abnormalities of extracellular matrix GAGs, limited to the mucosa in ulcerative colitis and greatest in the submucosa in Crohn's disease. There was also substantial loss of GAGs from the subepithelial basal lamina in both disorders and from the vascular endothelium in submucosa in Crohn's disease. The extent of local GAG disruption was associated with the distribution of macrophages immunoreactive for tumour necrosis factor alpha and the activation marker RM 3/1. We suggest that inflammatory disruption of vascular and connective tissue GAGs may be an important pathogenetic mechanism, contributing to the leakage of protein and fluid, thrombosis, and tissue remodelling seen in inflammatory bowel disease.

Adolescent↗
PubMed1993

Activation of mucosal V beta 3+ T cells and tissue damage in human small intestine by the bacterial superantigen, Staphylococcus aureus enterotoxin B.

Staphylococcus aureus enterotoxin B (SEB) was added to explants of fetal human intestine in organ culture or administered into the lumen of fetal small intestine prior to culture. Both routes produced a massive increase in lamina propria T cells expressing V beta 3, and to a lesser extent, those expressing V beta 5 and V beta 12. SEB-activated lamina propria T cells produced interleukin-2 and interferon-gamma and T cell activation was accompanied by tissue damage, which was inhibited by FK506.

Antigens, Bacterial↗
PubMed1993

Cyclosporin A enhances T cell-mediated induction of E-selectin.

In a fetal intestinal organ culture model of intestinal inflammation, activation of T cells by a lectin, superantigen or anti-CD3 antibodies induces E-selectin expression which peaks 6-10 h after activation and disappears by 24 h. We now show that addition of cyclosporin A (Cys A) increases the number of E-selectin-expressing endothelial cells and the intensity of expression, and it prolongs expression up to at least 60 h after stimulation. The dynamics of E-selectin expression on tumor necrosis factor activated human umbilical vein endothelial cell cultures is not affected by Cys A. Furthermore, other immunosuppressive agents FK506 and dexamethasone inhibit E-selectin expression, indicating that the enhancement observed in the presence of Cys A is not a consequence of general immunosuppression.

Cell Adhesion Molecules↗
PubMed1993

T-cell activation can induce either mucosal destruction or adaptation in cultured human fetal small intestine.

BACKGROUND: T-cell hypersensitivity is implicated in the tissue damage in a variety of gastrointestinal diseases. The aim of this study was to characterize the spectrum of pathological changes induced by T-cell activation in explants of fetal human small intestine, to modulate the pathology by immunological intervention, and to define the cellular pathways in intestinal damage. METHODS: Explants of fetal human small intestine were cultured with pokeweed mitogen in the presence or absence of dexamethasone or FK506. Pathological changes were then assessed by morphology or on frozen sections. RESULTS: Activation of lamina propria T cells produced variable mucosal damage that could be classified into two main types. Some explants showed villous atrophy and crypt hyperplasia whereas in others there was almost total mucosal destruction. This latter appearance predominated in explants from older specimens. Explants that were destroyed contained high numbers of T cells and activated macrophages. FK506 could completely inhibit mucosal damage, especially in younger specimens, whereas dexamethasone, even at high doses, prevented mucosal destruction, but individual explants continued to show villus atrophy and crypt hyperplasia. CONCLUSIONS: These results indicate that there is a quantitative relationship between mucosal cell-mediated immunity and the pathological outcome and that large numbers of activated macrophages in the mucosa can result in tissue destruction.

Adaptation, Physiological↗
PubMed1993

Diarrhoeal disease: current concepts and future challenges. Intestinal cytokines in inflammatory bowel disease and invasive diarrhoea.

In the intestine large numbers of bacteria and their products are separated by a single epithelial layer from resident inflammatory cells (macrophages and lymphocytes). Many of these bacterial products, such as lipopolysaccharides and peptidoglycans, are potent stimulators of free radical and inflammatory cytokine production by macrophages. This can occur in vivo in response to mucosal invasion by enteropathogenic bacteria or because of inappropriate activation of these cells, as in chronic inflammatory bowel disease. In this review we present evidence for production of cytokines in normal intestine and in intestinal inflammatory conditions. The adverse effects of cytokine production upon intestinal homeostasis, in particular disruption of epithelial integrity and prothrombotic changes in the vascular endothelium, are also discussed.

Cytokines↗
PubMed1993

Urinary growth hormone in growth-impaired children with chronic inflammatory bowel disease.

Growth impairment of undefined aetiology occurs in approximately 30% of children with chronic inflammatory bowel disease. We measured urinary growth hormone concentrations in 36 children with chronic inflammatory bowel disease and 51 normal controls. The median urinary concentration of growth hormone in the stunted children with chronic inflammatory bowel disease was 15.8 ng/g creatinine (range 4.3-32.6), compared with 11.7 ng/g creatinine (range 4.1-35.9) in those with normal growth. The difference was statistically not significant (p = 0.15). Moreover, there was no significant difference between the patients and the control group. One stunted patient had a urinary growth hormone (UGH) concentration below the normal range, whereas four patients with normal height were also below the normal range. Four of these five patients (80%) were on corticosteroid treatment at the time of urinary collection, whereas only 26% of the patients with normal UGH were also on corticosteroid treatment. We conclude that growth retardation in children with chronic inflammatory bowel disease is probably not related to growth hormone deficiency but must involve other mechanisms.

Adolescent↗
PubMed1993

Ontogeny and induction of adhesion molecule expression in human fetal intestine.

In this study we examined the distribution of the adhesion molecules ICAM-1, VCAM-1 and E-selectin in human fetal intestine, to determine whether they may have a role in the development of gut-associated lymphoid tissue. Secondly, we studied the tempo of induction of these molecules after T cell activation in explants of human fetal intestine cultured in vitro. In the fetus from 11 to 20 weeks gestation, endothelial expression of ICAM-1 and diffuse staining of VCAM-1 was observed in the lamina propria. In contrast, there was intense expression of ICAM-1 and VCAM-1 in the developing Peyer's patches, suggesting that these molecules may be involved in the accumulation or organization of lymphoid tissue in the gut. After T cell activation in fetal intestinal explants, the expression of ICAM-1 and VCAM-1 was increased on most endothelial cells, leucocytes, and stromal cells in the lamina propria. Expression was maintained for at least 4 days. In contrast, the induction of E-selectin was rapid, and the expression was transient, despite the continuing presence of activated T cells and macrophages. This suggests that other factors are required to prevent the down-regulation of E-selectin to maintain the sustained expression sometimes observed in vivo.

Antibodies, Monoclonal↗
PubMed1993

Location of tumour necrosis factor alpha by immunohistochemistry in chronic inflammatory bowel disease.

This study determined the location and tissue density of cells immunoreactive for tumour necrosis factor alpha (TNF alpha) in intestinal specimens from 24 patients with chronic inflammatory bowel disease (15 with Crohn's disease, nine with ulcerative colitis) and 11 controls. There was significantly increased density of TNF alpha immunoreactive cells in the lamina propria of both ulcerative colitis and Crohn's disease specimens, although the distribution of these cells differed in the two conditions. In ulcerative colitis most of the TNF alpha immunoreactivity was seen in the subepithelial macrophages, with comparatively less in the deep lamina propria, while in Crohn's disease immunoreactive cells were distributed evenly throughout the lamina propria. Increased submucosal immunoreactivity was found only in Crohn's disease, in which TNF alpha positive macrophages tended to cluster around arterioles and venules, often infiltrating and disrupting vascular endothelium. It is suggested that this degree of TNF alpha production probably contributes significantly to the pathogenesis of both Crohn's disease and ulcerative colitis, by impairing the integrity of epithelial and endothelial membranes, increasing inflammatory cell recruitment, and by prothrombotic effects on the vascular endothelium.

Adolescent↗
PubMed1993

Cytokines in stools of children with inflammatory bowel disease or infective diarrhoea.

AIMS: To determine the concentrations of interleukin-6 (IL-6) and tumour necrosis factor alpha (TNF alpha) in stools from children. METHODS: Stool samples from 14 healthy children, 32 children with inflammatory bowel disease, and 23 children with acute diarrhoea were emulsified in an equal volume of phosphate buffered saline and then centrifuged to produce a clear supernatant fluid. IL-6 and TNF alpha were measured by enzyme linked immunosorbent assay (ELISA). RESULTS: TNF alpha was detected in the stools of all 14 healthy children (12-130 pg/g stool), but IL-6 was detected only in three. Similar results were seen in children with inactive inflammatory bowel disease. Stool TNF alpha concentrations were raised in samples from children with active inflammatory bowel disease, but in most (11/18) of these samples IL-6 was undetectable. Stool samples contained a heat-labile factor which rapidly destroyed IL-6 immunoreactivity. Most children with diarrhoea had TNF alpha concentrations similar to those of healthy controls and most were also negative for IL-6. Three children with Shigella flexneri infection had extraordinarily high concentrations of both TNF alpha and IL-6 in their stools. CONCLUSIONS: There is constant low grade production of TNF alpha in the intestine of healthy people. Raised values are indicative of mucosal inflammation, but are not specific. Stool IL-6 is of little use in assessing mucosal inflammation because immunoreactivity is rapidly lost in stool samples.

Adolescent↗
PubMed1993

Interleukin-2- and interferon-gamma-secreting T cells in normal and diseased human intestinal mucosa.

A sensitive reverse haemolytic plaque assay to detect lymphokine-secreting T cells, and Northern blot analysis to detect expression of lymphokine messenger RNA (mRNA) were used to study interferon-gamma (IFN-gamma) and interleukin-2 (IL-2) production in the mucosa of children with Crohn's disease or ulcerative colitis (UC), and in histologically normal mucosa from patients without inflammatory bowel disease. In the mucosa of most patients with UC and control patients, IL-2- and IFN-gamma-secreting cells were absent or were present at only low levels. In contrast, in mucosa from patients with Crohn's disease, lymphokine-secreting cells were readily detectable (3-18%). IFN-gamma mRNA was detected by Northern blot analysis in 5/6 Crohn's tissues, but only in 1/5 UC samples and none of nine samples of control mucosa. These studies reveal an ongoing cell-mediated immune response in the mucosa in Crohn's disease.

Adolescent↗
PubMed1992

High endothelin-1 immunoreactivity in Crohn's disease and ulcerative colitis.

Both immunological hypersensitivity and vascular abnormalities have been implicated in the pathogenesis of inflammatory bowel disease. In an attempt to link the two hypotheses, we sought evidence of local production of endothelin-1, a potent vasoconstrictor, in patients with Crohn's disease and ulcerative colitis. An immunohistochemical method was used to detect endothelin-1 in tissue samples from sixteen Crohn's disease patients, nine ulcerative colitis patients, and thirteen controls. In the controls, positively staining cells were infrequent in both lamina propria (mean 0.9% of total cells, 95% confidence interval 0.1-1.7%) and submucosa (2.3%, 0.4-4.1%). The percentage of endothelin-immunoreactive cells was significantly higher in the two disease groups than in the controls. Among the Crohn's disease patients, there were more immunoreactive cells in the submucosa than in the lamina propria (19.1%, 15.2-22.1% vs 12.3%, 8.1-16.5%; p less than 0.001), whereas the converse was true for the ulcerative colitis group (8.6%, 1.1-16.1% vs 24.4%, 14.1-34.6%; p less than 0.001). Immunoreactive macrophage aggregates around submucosal blood vessels were common in samples from Crohn's disease patients. Endothelin concentrations, measured by radioimmunoassay, in supernatants of homogenised tissue samples were significantly higher in Crohn's disease and ulcerative colitis than in controls. We suggest that local endothelin production by inflammatory cells may contribute to vasculitis in chronic inflammatory bowel disease by inducing intestinal ischaemia through vasoconstriction.

Adolescent↗
PubMed1992

Tumour necrosis factor alpha in stool as a marker of intestinal inflammation.

Measurement of disease activity in patients with inflammatory bowel disease is difficult. The best available methods are complex and time consuming, but it may be possible to use tumour necrosis factor alpha (TNF alpha) concentration in stool as a marker of disease activity. We measured TNF alpha concentrations in stool samples from normal children, infants with diarrhoea, and children with inflammatory bowel disease in active and inactive phases of the disease. In 10 normal children and 14 children with diarrhoea, median stool TNF alpha concentrations were 58 and 45 pg/g stool, respectively. Compared with diarrhoeal controls, stool TNF alpha concentrations were significantly increased in children with active Crohn's disease (n = 13, median 994 pg/g, p less than 0.0002) and active ulcerative colitis (n = 4, range 276-5982 pg/g, p less than 0.003). In patients with inactive disease, either as a result of surgery or treatment with steroids, the concentration of stool TNF alpha fell to those of controls. Measurement of stool TNF alpha concentrations may provide a simple way to monitor disease activity in inflammatory bowel disease.

Adolescent↗