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Biomedical subjects

A G Cummins

Publications and source records attributed to A G Cummins.

At least 37 records · Page 2Linked to original sources
PubMed1994

Neuropeptide depletion by capsaicin does not prevent mucosal mast cell activation in the rat at weaning.

Substance P release by enteric nerves could be an initiating factor for mucosal mast cell (MMC) activation that is associated with weaning in the rat. Capsaicin, which depletes substance P from enteric nerves, should therefore prevent MMC degranulation. Rat pups received either capsaicin (50 mg/kg) or vehicle control subcutaneous injections at 3 and 6 days of life. Capsaicin-treated and control litters were killed at 16, 18, 20, 22, 24 and 26 days of life. MMC activation was measured by serum levels of rat mast cell protease II (RMCPII). Intestinal development was assessed by microdissection to measure villus area, crypt length and crypt cell production rate. RMCPII levels were similar in capsaicin-treated and control rats and peaked at day 22 of life, and intestinal development was not retarded by capsaicin treatment. We conclude that substance P release is unlikely to be an initiating factor for the MMC activation that is associated with weaning.

Animals↗
PubMed1994

Phenotype of T cells, their soluble receptor levels, and cytokine profile of human breast milk.

Human breast milk has important immunoprotective and immunosuppressive functions for an infant. The purpose of this study was to extend the phenotype of milk cells and to measure soluble T cell receptor levels and cytokines in milk, and to compare these with neonatal and adult blood. Milk T cells had a more equivalent CD4:CD8 ratio than blood; milk CD4 T cells mainly expressed the CD45RO (antigen primed/memory) phenotype; milk CD8 cells had an equivalent CD11b:CD28 suppressor:cytotoxic phenotype; and milk T cells had 2-3-fold higher percentages of activated CD4 IL-2R and CD8 HML-1 or CD8 VLA-1 cells than blood. Soluble IL-2R, CD4 and CD8 concentrations were lower in milk than adult blood, although relatively increased when compared to the lower T cell concentration in milk. Breast milk contained high levels of IFN-gamma but low levels of other measured cytokines compared to blood. These distinct differences of T cells and their soluble products are likely to influence an infant's immune system.

Adult↗
PubMed1991

Phenotype and activation of milk-derived and peripheral blood lymphocytes from normal and coeliac subjects.

The phenotype of milk-derived and peripheral blood lymphocytes from normal and coeliac subjects was assessed for CD3, alpha beta-TcR (T cell receptor), gamma delta-TcR, CD4, CD8, HML-1 (human mucosal lymphocyte) determinants, and activation was measured by interleukin-2 receptor (IL-2R) expression. Milk cells from normal and coeliac subjects were analysed by manual immunofluorescence and milk and blood cells from normal subjects were analysed by flow cytometry. Milk cells from two coeliac subjects were tested for proliferation to gluten antigen. The CD4:CD8 ratio of milk lymphocytes from both normal and coeliac subjects was similar (0.78-1.1), but lower than that present in blood (1.5-2.1). The IL-2R expression of milk lymphocytes from both coeliac and normal subjects was increased by 3-6 times compared with peripheral blood cells. For example, IL-2R was present on 27.3% of milk CD3+ lymphocytes and on 8.0% of blood CD3+ lymphocytes from normal subjects. gamma delta- and HML-1+ T cells were increased 4.2-fold and 12-fold respectively compared with blood lymphocytes. Milk cells from coeliac subjects showed specific proliferation to gluten but not to soya bean antigen. We conclude that milk cells have a 'mucosal' phenotype, with increased gamma delta-TcR, CD8+ and HML-1+ T cells, and have an increased proportion of activated cells. Milk cells from coeliac subjects have no 'toxic' phenotype, but show functional reactivity by specific proliferation to gluten antigen.

Antigens↗
PubMed1991

Mucosal immune activation and maturation of the small intestine at weaning in the hypothymic (nude) rat.

Activation of the mucosal immune system peaks at weaning on days 21 and 22 of life in the rat. We have investigated activation in the gut associated lymphoid tissue and maturation of intestinal mucosa in hypothymic (nude) and in phenotypically normal heterozygous CBH rats at 22 days of life. Intestinal maturation, as assessed by villus area, crypt length, crypt cell production rate and disaccharidase activity, was similar in hypothymic and normal rats, and indices of mucosal immune function were elevated in both groups at this time. The proportion of mononuclear cells from the mesenteric lymph node expressing IL-2R was 11% in heterozygous and 14% in hypothymic rats as determined by flow cytometry. Immunoperoxidase staining of MLN sections confirmed the presence of IL-2R+ cells in the T-dependent interfollicular areas. However, the number of T-cells was considerably depleted in hypothymic rats. Intraepithelial lymphocyte counts and serum rat mucosal mast cell protease II concentrations were similar in the two groups, while counts of jejunal mucosal mast cells and eosinophils were paradoxically increased in hypothymic animals. As T lymphocyte function is thought to be impaired in hypothymic rats, the intact mucosal immune activity in hypothymic rats could be due to activation of intrinsic "thymic independent" T lymphocytes in hypothymic rats, or to engraftment with extrinsic maternal milk-derived lymphocytes and their activation in the infant rat gut.

Animals↗
PubMed1990

Lymphocyte activation as measured by interleukin-2 receptor expression to gluten fraction 111 in coeliac disease.

Lymphocyte activation was examined by interleukin-2 (IL-2) receptor expression on peripheral blood mononuclear cells from coeliac and control subjects. Purified T cells were incubated with gluten fraction 111 (a known toxic peptide for coeliac subjects), soyabean hydrolysate (an unrelated hydrolysed food antigen), and Concanavalin-A (Con-A, a non-specific mitogen). After 1-5 days incubation, expression of IL-2 receptors was assessed using a cellular enzyme-linked immunosorbent assay (ELISA). Gluten fraction 111 induced expression of IL-2 receptors on T lymphocytes from coeliac but not from normal subjects (P = 0.0005), whereas soyabean hydrolysate did not induce IL-2 receptor expression. Lymphocytes from both coeliac and normal subjects had similar increased IL-2 receptor expression after incubation with Con-A. Flow cytometry was also used to confirm specific expression of IL-2 receptor expression of lymphocytes from coeliac subjects. Interleukin-2 receptor expression increased from 0 to 5.4% of cultured mononuclear cells after 7 days incubation with gluten fraction III. These cells were CD3-positive and CD4-positive. We conclude that peripheral blood lymphocytes from coeliac subjects are sensitized specifically to gluten fraction III.

Analysis of Variance↗
PubMed1990

Quantitative histological study of enteropathy associated with HIV infection.

A quantitative histological study was performed on small intestinal biopsies from eight ambulatory patients with HIV infection (AIDS/AIDS-related complex, ARC) and compared with those from 16 normal subjects. Enteropathy was assessed by measurement of villus area, crypt length and mitotic count, as well as duodenal counts of intraepithelial lymphocytes, mucosal mast cells and goblet cells. Enteropathy in subjects with AIDS/ARC was shown by reduced mean villus area of 0.363 (SD 0.081) compared with 0.500 (SD 0.064) mm2 in control subjects (p less than 0.0001), while intestinal crypts were of similar length with 239 (SD 36) compared with 225 (SD 28 microns, but mitotic count was increased to 3.8 (SD 1.2) compared with 2.4 (SD 0.8) (p = 0.01) in the same control subjects. These results indicate villous atrophy with impaired crypt hyperplasia. Duodenal cell counts showed similar numbers of mucosal mast cells, intraepithelial lymphocytes and goblet cells in AIDS/ARC patients and fifteen control subjects.

AIDS-Related Complex↗
PubMed1989

Effect of cyclosporin A treatment on the enteropathy of graft-versus-host reaction in the rat: a quantitative study of intestinal morphology, epithelial cell kinetics and mucosal immune activity.

Mucosal graft-versus-host reaction (GvHR) of the small intestine exemplifies an immunologically mediated enteropathy that is associated with expansion of mucosal mast cells (MMC). Quantitative measures of intestinal morphology, epithelial cell kinetics and mucosal immune activity were used to assess the effect of the immunosuppressive agent, cyclosporin A (CyA), in ameliorating this enteropathy and on increased activity of MMC in the jejunum. GvHR was induced in two groups of PVGU x PVGC rats by irradiation (4.50 Gy) and intravenous injection of PVGC spleen cells (150 x 10(6)). One group remained untreated, while a second group of eight rats was treated with a 50 mg/kg dose of CyA subcutaneously given daily for the first 3 days and then every second day, and which had commenced the day before induction of GvHR. On day 14, all animals were killed. Treatment with CyA prevented intestinal crypt hyperplasia but did not affect villus length, and normalized the crypt cell production rate (CCPR) from 38 to 15 cells/crypt/h (P less than 0.0001). CyA reduced the number of MMC and jejunal content of the MMC associated protease, rat mucosal mast cell protease II (RMCPII). Mean serum RMCPII concentration was reduced from 302 (s.d. = 112) in GvHR animals to 10 (s.d. = 6) ng/mL in GvHR/CyA-treated rats (P less than 0.0001). We conclude that CyA ameliorates the enteropathy of GvHR and depresses the activation of MMC, as evident by the strongly depressed serum RMCPII concentration.

Animals↗
PubMed1989

Separate effects of irradiation and of graft-versus-host reaction on rat mucosal mast cells.

T cell mediated immune responses in the gut can produce enteropathy and malabsorption. We have investigated the relevance of mucosal mast cells (MMC) to the mechanisms of this enteropathy by using graft-versus-host reaction (GvHR) in the rat as a model of mucosal delayed type hypersensitivity. Measurements of mucosal architecture, intraepithelial lymphocytes (IEL) and MMC counts were performed in control and experimental rats, and release of rat mast cell protease II (RMCPII) into the bloodstream was used as an index of MMC activation. In unirradiated rats, jejunal MMC count was increased on day 14 of the GvHR (mean 272/mm2 v 182 in controls, p less than 0.01), as was serum RMCPII (p less than 0.01). Irradiated rats (4.5 Gy, reconstituted with isogeneic spleen cells) had low counts of IEL and crypt hyperplasia seven to 14 days after irradiation. Irradiated rats with GvHR (induced by ip injection of parental strain spleen cells) and studied on days 7, 10 and 14, had significant enteropathy with longer crypts and higher CCPR than matched irradiated animals (p less than 0.05 on day 14 when compared with irradiation alone). Intraepithelial lymphocytes counts, however, reflected only the effect of radiation. Irradiation, with or without GvHR, led to the virtual disappearance of jejunal MMC, undetectable jejunal RMCPII and very low levels of RMCPII in serum (all p less than 0.01 when compared with unirradiated controls). These experiments show that there is a modest expansion in jejunal MMC in unirradiated rats with semiallogeneic GvHR, whereas irradiation, alone or associated with GvHR, profoundly depletes MMC for at least two weeks. The enteropathy of GvHR can evolve in the virtual absence of MMC.

Animals↗
PubMed1989

The effect of cyclosporin A in delaying maturation of the small intestine during weaning in the rat.

As maturation of the small intestine has similar features to an immunologically mediated reaction, we studied the effect of the immunosuppressive agent, cyclosporin A (CyA), on the development of the small intestine during weaning in the DA x PVG rat. Intestinal development was measured by villus area, crypt length, crypt cell production rate (CCPR), and disaccharidase activity. Rat pups received either cyclosporin A (7.5 mg/kg daily subcutaneously) or polyethoxylated castor oil (Cremophor, drug vehicle) subcutaneously from 12 days of age. Cremophor- and CyA-treated litters were killed at 18, 20, 22, 24, and 26 days of age. CyA-treated animals had retarded weight gain, lower mesenteric lymph node and spleen weights, fewer intraepithelial lymphocytes, and reduced systemic secretion of rat mucosal mast cell protease II. CyA treatment retarded any increase in villus area, crypt length and CCPR until day 26 of age. Lactase activity was retained longer, and sucrase and maltase induction was delayed. We conclude that CyA retarded normal development of the small intestine, but some maturation still occurred at the end of weaning.

Animals↗
PubMed1988

Maturation of the rat small intestine at weaning: changes in epithelial cell kinetics, bacterial flora, and mucosal immune activity.

The relationship between maturation of the small intestine and change in mucosal immune activity was examined in the DA rat during the weaning period from 12 to 30 days. Two stages of jejunal maturation were observed: an initial stage of morphological development and crypt proliferation (days 12 to 22), followed by a period of stabilisation (days 24 to 30). By day 22 of the initial phase, villi increased principally in width but not in length, crypt length increased, and crypt cell production rate increased from 0.5 (day 12) to 11.1 (day 22) cells/crypt/hour. Various measures of mucosal immune activity showed a biphasic response. Up to days 20 to 22, the weight of the mesenteric lymph node increased seven-fold (p less than 0.0001), counts of jejunal eosinophils and goblet cells increased 3- (p less than 0.0001) and 19-fold (p less than 0.0001) respectively, and mean serum rat mucosal mast cell protease II, released from mucosal mast cells, increased from 24 (day 12) to 313 (day 22) ng/ml (p less than 0.0001). After day 22, mesenteric lymph node weight stabilised, eosinophil count stabilised and goblet cells decreased, serum rat mucosal mast cell protease II decreased three-fold (p less than 0.0001), and mean jejunal count of intraepithelial lymphocytes increased from 26 (day 22) to 54 (day 24) cells per mm of muscularis mucosae (p less than 0.0001), before stabilising. These results demonstrated a close association between maturation of the small intestine and change in activity of the mucosal immune system.

Animals↗
PubMed1988

Effect of cyclosporin A on rat mucosal mast cells and the associated protease RMCPII.

The effects of Cyclosporin A (CyA) on rat mucosal mast cells (MMC) have been investigated by cell counts in the jejunal mucosa and assays of the MMC-specific granule protease RMCPII in tissues and serum. CyA was administered by subcutaneous injection; for the majority of experiments the rats received 50 mg/kg daily for 3 days as a loading dose, then 50 mg/kg on alternate days. Treatment with this drug has two actions on MMC, a gradual reduction in the number of MMC and in the tissue content of RMCPII in the jejunum; and a rapid fall in the serum concentration of RMCPII, detectable 3 h after i.v. administration of CyA, 50 mg/kg. These phenomena were demonstrated in normal rats and in animals with an expanded jejunal MMC population due to graft vs host reaction or recent helminth infection. The functional relevance of the MMC depletion was demonstrated in immune rats given CyA for 3 days prior to induction of systemic anaphylaxis; intestinal permeability to i.v. Evan's blue was significantly reduced by CyA treatment. We suggest that CyA depletes intestinal MMC by suppression of T-cell-mediated regulatory stimuli to proliferation of mast cell precursors and/or their migration. The effects of the drug on serum RMCPII, evident before there were changes in the number of intestinal MMC, indicate that it also suppresses the secretion of granule mediators by MMC, probably indirectly via effects on mucosal T cells.

Anaphylaxis↗
PubMed1987

The effect of protein deficiency on systemic release of rat mucosal mast cell protease II during Nippostrongylus brasiliensis infection and following systemic anaphylaxis.

Serum rat mucosal mast cell protease II (RMCPII) was measured in protein-deficient rats to assess mucosal mast cell (MMC) activation during primary infection with the nematode, Nippostrongylus brasiliensis, and during systemic anaphylaxis produced by Nippostrongylus antigen in immune animals. In the first study, serum RMCPII increased 4-fold by day 15 after infection. By day 20, serum RMCPII continued to rise in protein-deficient animals, but decreased in nutritionally normal animals. This was associated with impaired worm rejection in protein-deficient rats. During systemic anaphylaxis, serum RMCPII was elevated in three groups of protein-deficient rats on 6%, 8% and 10% low protein diets and in nutritionally normal rats. All protein-deficient rats exhibited 3 to 7-fold less mucosal permeability of the small intestine to Evan's blue dye injected intravenously compared to nutritionally normal animals following anaphylactic stimulation. These results demonstrated that MMC are activated during infection in protein deficiency, and suggest that reduced MMC function does not explain delay in worm expulsion. Impaired mucosal anaphylaxis in protein deficiency could not be attributed to a failure of MMC response.

Anaphylaxis↗
PubMed1987

Roles of mucosal mast cells in intestinal cell-mediated immunity.

Mucosal mast cells in rats with GvHR have been studied by cell counts, tissue levels of the specific protease RMCPII, and, as an index of MMC activation, serum RMCPII. In semi-allogeneic GvHR without host irradiation, GvHR produced modest increases in these three indices. In contrast, irradiation profoundly depleted MMC even though enteropathy was more severe than in non-irradiated hosts. We suggest that enteropathy is not dependent on the presence of MMC. In rats given cyclosporin A, lesions of GvHR were mild and numbers of MMC were low.

Animals↗
PubMed1986

Blood loss during Nippostrongylus brasiliensis infection in the rat.

Faecal blood loss was measured during Nippostrongylus brasiliensis infection in the DA rat using 51Cr-labelled red blood cells (r.b.c.s). In an initial study, faecal blood loss was measured on day 7 of primary infection with 3000 larvae administered subcutaneously (s.c.), and found to be 0.03 ml/24 h in uninfected animals and 0.14 ml/24 h in infected animals. In a further experiment, blood loss was measured on the day before infection and for 13 days after primary s.c. infection with 5000 larvae. Faecal blood loss was 0.05 ml/24 h or less until day 3, began to rise from day 5, reached a peak of 0.51 ml/24 h on day 8, and fell until day 13. This was closely associated with the rise and fall of the pooled faecal egg count. Direct worm count confirmed a high worm burden on day 7 and expulsion by day 14. The effect of the worm burden on the haemoglobin concentration (Hb) was measured in a further experiment and showed a fall in Hb with a mean worm burden of 726 compared to that of 47 or 284 worms. The study concluded that there is minimal background blood loss in uninfected rats but that infection with N. brasiliensis is a cause of intestinal blood loss and this is associated with a fall in Hb concentration that is dependent on the worm burden.

Analysis of Variance↗