Intestinal Immunoglobulin A Levels Research Articles

Lactobacillus rhamnosus alters intestinal IgA levels and IgA–microbiota interactions in healthy mice in a strain-specific manner

Immunoglobulin A (IgA), a mucosal immune antibody, exhibits different degrees of affinity to intestinal bacteria and performs a diverse range of immune functions. IgA secretion is closely related to microbial stimulation. The stimulation pathways and effects of pathogenic intestinal bacteria and probiotics are reported to be different. However, it is unclear whether the mode of action between probiotics, gut microbiota, and IgA in healthy hosts varies depending on strain differences. In this study, six different strains of Lactobacillus rhamnosus from humans were used to investigate the differences in their effects on IgA levels and the gut microbiota affinitive to IgA in the intestines of healthy mice. It was found that six strains of L. rhamnosus exerted different effects on IgA levels and IgA-coated bacteria in the intestines of healthy mice. Short-term administration of L. rhamnosus CCFM1228, 28L2 and W6L1 improved the secretion of intestinal IgA and the IgA index values for Escherichia–Shigella, Pseudomonas, and other potential pathogens. However, for other species in the intestinal, L. rhamnosus strains showed different trends in their regulatory effects. L. rhamnosus CCFM1228 decreased the affinity of IgA for Enterococcus and increased the IgA index values for Alistipes and Alloprevotella. But L. rhamnosus 66L1 and W6L1 significantly increased the affinity of IgA for Pseudomona. However, this change was not significantly correlated with caecal SCFA levels or colonic inflammatory factors. Finally, only L. rhamnosus 66L1, CCFM1228, and W6L1, which enhanced 1 week faecal IgA concentration, promoted the transcription level of ACIDA. This study helps to provide new insights into the effect of L. rhamnosus on the intestinal IgA level and IgA–microbiota interactions in the gut of healthy hosts, thus supporting the individualized selection of probiotics for immune intervention.

Probiotics induce intestinal IgA secretion in weanling mice potentially through promoting intestinal APRIL expression and modulating the gut microbiota composition.

Intestinal infections are strongly associated with infant mortality, and intestinal immunoglobulin A (IgA) is important to protect infants from intestinal infections after weaning. This study aims to screen probiotics that can promote the production of intestinal IgA after weaning and further explore their potential mechanisms of action. In this study, probiotics promoting intestinal IgA production were screened in weanling mouse models. The results showed that oral administration of Bifidobacterium bifidum (B. bifidum) FL228.1 and Bifidobacterium bifidum (B. bifidum) FL276.1 significantly enhanced IgA levels in the small intestine and upregulated the expression of a proliferation-inducing ligand (APRIL) and its upstream regulatory factor toll-like receptor 4 (TLR4). Furthermore, B. bifidum FL228.1 upregulated the relative abundance of Lactobacillus, while B. bifidum FL276.1 increased the relative abundance of Marvinbryantia and decreased Mucispirillum, further elevating intestinal IgA levels. In summary, B. bifidum FL228.1 and B. bifidum FL276.1 can induce IgA production in the intestinal tract of weanling mice by promoting intestinal APRIL expression and mediating changes in the gut microbiota, thus playing a significant role in enhancing local intestinal immunity in infants.

Phenotypic and genomic characterisation of performance of tropically adapted chickens raised in smallholder farm conditions in Ethiopia.

In sub-Saharan Africa, 80% of poultry production is on smallholder village farms, where chickens are typically reared outdoors in free-ranging conditions. There is limited knowledge on chickens' phenotypic characteristics and genetics under these conditions. The present is a large-scale study set out to phenotypically characterise the performance of tropically adapted commercial chickens in typical smallholder farm conditions, and to examine the genetic profile of chicken phenotypes associated with growth, meat production, immunity, and survival. A total of 2,573 T451A dual-purpose Sasso chickens kept outdoors in emulated free-ranging conditions at the poultry facility of the International Livestock Research Institute in Addis Ababa, Ethiopia, were included in the study. The chickens were raised in five equally sized batches and were individually monitored and phenotyped from the age of 56days for 8weeks. Individual chicken data collected included weekly body weight, growth rate, body and breast meat weight at slaughter, Newcastle Disease Virus (NDV) titres and intestinal Immunoglobulin A (IgA) levels recorded at the beginning and the end of the period of study, and survival rate during the same period. Genotyping by sequencing was performed on all chickens using a low-coverage and imputation approach. Chicken phenotypes and genotypes were combined in genomic association analyses. We discovered that the chickens were phenotypically diverse, with extensive variance levels observed in all traits. Batch number and sex of the chicken significantly affected the studied phenotypes. Following quality assurance, genotypes consisted of 2.9 million Single Nucleotide Polymorphism markers that were used in the genomic analyses. Results revealed a largely polygenic mode of genetic control of all phenotypic traits. Nevertheless, 15 distinct markers were identified that were significantly associated with growth, carcass traits, NDV titres, IgA levels, and chicken survival. These markers were located in regions harbouring relevant annotated genes. Results suggest that performance of chickens raised under smallholder farm conditions is amenable to genetic improvement and may inform selective breeding programmes for enhanced chicken productivity in sub-Saharan Africa.

Oxidative stress-related markers as prognostic factors for patients with primary sclerosing cholangitis in Japan.

Primary sclerosing cholangitis (PSC) is a rare chronic liver disease. The mechanisms and prediction of PSC progression are unclear. Recent investigations have shown that general conditions, such as oxidative stress, affect the course of chronic diseases. We investigated the clinical course and oxidative stress-related condition of PSC to determine prognostic factors. We recruited 58 patients with PSC (mean age; 37.4years, mean observation period; 1382days) who visited our department from 2003 to 2021. Clinical characteristics were investigated to define prognostic factors. Oxidative stress status was evaluated using two types of markers: an oxidative stress marker (serum reactive oxygen metabolite; dROM) and an antioxidant marker (serum OXY adsorbent test; OXY). The revised Mayo risk, Child-Pugh, model for end-stage liver disease-sodium (MELD-Na) scores or fibrosis-related FIB-4 index significantly predicted poor overall survival. High intestinal immunoglobulin A (IgA) levels predicted poor survival. Among patients with high and intermediate revised Mayo risk scores, those with physiologically high dROM levels showed better survival than those with lower dROM levels. In this population, dROM was negatively correlated with AST and IgA, which are both correlated with survival. High and intermediate revised Mayo risk score group predicted a poor clinical course in PSC. Additionally, the Child-Pugh score, MELD-Na score, FIB-4 index, and serum IgA were significantly correlated with survival. In patients with high and intermediate revised Mayo risk scores, physiologically high oxidative stress status correlated with low IgA levels and a good prognosis.

Dietary supplement of mushrooms promotes SCFA production and moderately associates with IgA production: A pilot clinical study.

Mushrooms are rich in dietary fiber, and fiber intake has been reported to increase the levels of short-chain fatty acids (SCFAs). It has also been reported that SCFAs promote immunoglobulin A (IgA) production, indicating involvement in systemic immunity. The objective of this study was to evaluate the effects of mushroom consumption on the amount of intestinal IgA. We also aimed to comprehensively evaluate the gut microbiota and intestinal metabolome and to conduct an exploratory analysis of their relationship with IgA. Healthy adults (n = 80) were enrolled in a parallel group trial. Participants consumed a diet with mushrooms or a placebo diet once daily for 4 weeks. Gut microbiota profiles were assessed by sequencing the bacterial 16S ribosomal RNA-encoding gene. Intestinal metabolome profiles were analyzed using capillary electrophoresis-time of flight mass spectrometry (CE-TOFMS). Mushroom consumption tended to increase IgA levels at 4 weeks of consumption compared to those in the control group (p = 0.0807; Hedges' g = 0.480). The mushroom group had significantly higher levels of intestinal SCFAs, such as butyrate and propionate, than the control group (p = 0.001 and 0.020; Hedges' g = 0.824 and 0.474, respectively). Correlation analysis between the changes in the amount of intestinal IgA and the baseline features of the intestinal environment showed that the increasing amount of intestinal IgA was positively correlated with the baseline levels of SCFAs (Spearman's R = 0.559 and 0.419 for butyrate and propionate, respectively). Consumption of mushrooms significantly increased the intestinal SCFAs and IgA in some subjects. The increase in intestinal IgA levels was more prominent in subjects with higher SCFA levels at baseline. This finding provides evidence that mushroom alters the intestinal environment, but the intensity of the effect still depends on the baseline intestinal environment. This trial was registered at www.umin.ac.jp as UMIN000043979.

The role of retinoic acid in the production of immunoglobulin A.

Vitamin A and its derivative retinoic acid (RA) play important roles in the regulation of mucosal immunity. The effect of vitamin A metabolism on T lymphocyte immunity has been well documented, but its role in mucosal B lymphocyte regulation is less well described. Intestinal immunoglobulin A (IgA) is key in orchestrating a balanced gut microbiota composition. Here, we describe the contribution of RA to IgA class switching in tissues including the lamina propria, mesenteric lymph nodes, Peyer's patches and isolated lymphoid follicles. RA can either indirectly skew T cells or directly affect B cell differentiation. IgA levels in healthy individuals are under the control of the metabolism of vitamin A, providing a steady supply of RA. However, IgA levels are altered in inflammatory bowel disease patients, making control of the metabolism of vitamin A a potential therapeutic target. Thus, dietary vitamin A is a key player in regulating IgA production within the intestine, acting via multiple immunological pathways.

Evaluation of intestinal microbiota, short-chain fatty acids, and immunoglobulin a in diversion colitis

It is reported that an increase in aerobic bacteria, a lack of short-chain fatty acids (SCFAs), and immune disorders in the diverted colon are major causes of diversion colitis. However, the precise pathogenesis of this condition remains unclear. The aim of the present study was to examine the microbiota, intestinal SCFAs, and immunoglobulin A (IgA) in the diverted colon. Eight patients underwent operative procedures for colostomies. We assessed the diverted colon using endoscopy and obtained intestinal samples from the diverted colon and oral colon in these patients. We analyzed the microbiota and SCFAs of the intestinal samples. The bacterial communities were investigated using a 16S rRNA gene sequencing method. The microbiota demonstrated a change in the proportion of some species, especially Lactobacillus, which significantly decreased in the diverted colon at the genus level. We also showed that intestinal SCFA values were significantly decreased in the diverted colon. Furthermore, intestinal IgA levels were significantly increased in the diverted colon. This study was the first to show that intestinal SCFAs were significantly decreased and intestinal IgA was significantly increased in the diverted colon. Our data suggest that SCFAs affect the microbiota and may play an immunological role in diversion colitis.

Interleukin (IL)-21 promotes intestinal IgA response to microbiota.

Commensal microbiota-specific Th17 cells are enriched in the intestines, which can convert into Tfh in Peyer’s patches, and are crucial for production of intestinal IgA against microbiota, however, the role of Th17 and Tfh cytokines in regulating the mucosal IgA response to enteric microbiota is still not completely known. In this study, we found that intestinal IgA was impaired in mice deficient in IL-17 or IL-21 signaling. IL-21, but not IL-17, is able to augment B cell differentiation to IgA+ cells as mediated by TGFβ1, and accelerate IgA class switch recombination (CSR). IL-21 and retinoic acid (RA) induce IgA+ B cell development and IgA production, and drives autocrine TGFβ1 production to initiate IgA CSR. Repletion of T cell-deficient TCRβxδ−/− mice with Th17 cells specific for commensal bacterial antigen, increased levels of IgA+ B cells and IgA production in the intestine, which was blocked by neutralizing IL-21. Thus, IL-21 functions to strongly augment IgA production under intestinal environment. Furthermore, IL-21 promotes intestinal B cell homing through α4β7 expression, alone or with TGFβ and RA. Together, IL-21 from microbiota-specific Th17 and/or Tfh cells contributes to robust intestinal IgA levels by enhancing IgA+ CSR, IgA production, and B cell trafficking into the intestine.

Parenteral glutamine supplementation in combination with enteral nutrition improves intestinal immunity in septic rats

ObjectivesThe gut-associated lymphoid tissue is continuously exposed to antigens in the gut lumen and becomes the first line of defense against enteric bacteria and associated toxin. The aim of this study was to investigate the effects of parenteral glutamine (GLN) supplementation in combination with enteral nutrition (EN) on intestinal mucosal immunity in septic rats by cecal ligation and puncture (CLP). MethodsMale Sprague-Dawley rats were randomly assigned into four groups: A sham CLP + EN + saline group (n = 10), a sham CLP + EN + GLN group (n = 10), a CLP + EN + saline group (n = 10), and a CLP + EN + GLN group (n = 10). At 2 h after CLP or sham CLP, all rats in each of the four groups received an identical enteral nutrition solution as their base formula. Then, the rats in the sham CLP + EN + GLN group and CLP + EN + GLN group were given 0.35 g GLN/kg body weight daily for 7 d, all at the same time, via a tail vein injection; whereas those in the sham CLP + EN + saline group and CLP + EN + saline group were daily administered isovolumic sterile 0.9% saline for comparison. All rats in each of the four groups were given 290 kcal/kg body wt/d for 7 d. At the end of the seventh day after the nutritional program was finished, all rats were euthanized and the entire intestine was collected. Total Peyer's patches (PP) cell yield was counted by a hemocytometer. The percentage of PP lymphocyte subsets was analyzed by flow cytometry. The number of intestinal lamina propria IgA plasma cells was determined by the immunohistochemistry technique. The intestinal immunoglobulin A (IgA) levels were assessed by ELISA. PP apoptosis was evaluated by terminal deoxyuridine nick-end labeling. ResultsThe results revealed total PP cell yield, the numbers of PP lymphocyte subsets, intestinal lamina propria IgA plasma cells, and intestinal IgA levels in the CLP + EN + GLN group were significantly increased when compared with the CLP + EN + saline group (P < 0.05). On the other hand, the number of TUNEL-stained cells within PPs in the CLP + EN + GLN group was markedly decreased as compared with the CLP + EN + saline group (P < 0.05). ConclusionThe results of this study show that parenteral glutamine supplementation in combination with enteral nutrition may attenuate PP apoptosis, increase PP cell yield and intestinal lamina propria IgA plasma cells, and subsequently improve intestinal mucosal immunity. Clinically, these results suggest therapeutic efforts at improving intestinal immunity may contribute to the prevention and treatment of sepsis.

Decreased serum and mucosa immunoglobulin A levels in vitamin Aand zinc-deficient mice.

Simultaneous zinc and vitamin A deficiency are common health problems in developing countries. The objective of this study was to assess the effect of vitamin A- and zinc-deficient diet on immunoglobulin A (IgA) response. Six-week-old mice were assigned into two groups receiving a normal vitamin A and zinc or low vitamin A and zinc diet for five months. Serum and intestinal mucosa IgA levels were determined by the enzyme-linked immunosorbent assay method. The concentration of zinc in serum was determined using an inductively coupled plasma mass spectrometer. Vitamin A measurement in serum was carried out by high performance liquid chromatography. Mice maintained on a low vitamin A and zinc diet showed significantly greater food intake but lower production of IgA both in serum and mucosa. A mucosa IgA level was significantly higher in both control and deficient groups than the serum IgA level. Results indicated that zinc and vitamin A deficiency is associated with a lower production of IgA. Micronutrient intervention strategies addressing IgA-related gastrointestinal infections are needed.

Effects of Adding Butyric Acid to PN on Gut‐Associated Lymphoid Tissue and Mucosal Immunoglobulin A Levels

Parenteral nutrition (PN) causes intestinal mucosal atrophy, gut-associated lymphoid tissue (GALT) atrophy and dysfunction, leading to impaired mucosal immunity and increased susceptibility to infectious complications. Therefore, new PN formulations are needed to maintain mucosal immunity. Short-chain fatty acids have been demonstrated to exert beneficial effects on the intestinal mucosa. We examined the effects of adding butyric acid to PN on GALT lymphocyte numbers, phenotypes, mucosal immunoglobulin A (IgA) levels, and intestinal morphology in mice. Male Institute of Cancer Research mice (n = 103) were randomized to receive either standard PN (S-PN), butyric acid-supplemented PN (Bu-PN), or ad libitum chow (control) groups. The mice were fed these respective diets for 5 days. In experiment 1, cells were isolated from Peyer's patches (PPs) to determine lymphocyte numbers and phenotypes (αβTCR(+), γδTCR(+), CD4(+), CD8(+), B220(+) cells). IgA levels in small intestinal washings were also measured. In experiment 2, IgA levels in respiratory tract (bronchoalveolar and nasal) washings were measured. In experiment 3, small intestinal morphology was evaluated. Lymphocyte yields from PPs and small intestinal, bronchoalveolar, and nasal washing IgA levels were all significantly lower in the S-PN group than in the control group. Bu-PN moderately, but significantly, restored PP lymphocyte numbers, as well as intestinal and bronchoalveolar IgA levels, as compared with S-PN. Villous height and crypt depth in the small intestine were significantly decreased in the S-PN group vs the control group, however Bu-PN restored intestinal morphology. A new PN formula containing butyric acid is feasible and would ameliorate PN-induced impairment of mucosal immunity.

Effects of early enteral nutrition supplemented with arginine on intestinal mucosal immunity in severely burned mice

To investigate the effects of early enteral nutrition (EN) supplemented with Arginine (Arg) on intestinal mucosal immunity in severely burned mice. Forty-four mice were randomly assigned into four groups: a sham injury+EN group (n=10), a sham injury+EN+Arg group (n=10), a burn+EN group (n=12), and a burn+EN+Arg group (n=12) and the mice in two experimental groups received a 20% total body surface area (TBSA), full-thickness scald burn on the back. Then, the burned mice were given a 175 kcal/kg body wt/day of conventional enteral nutrition or an isonitrogenous and isocaloric enteral nutrition supplemented with Arg by gastric gavage for 7 days. There was isonitrogenous and isocaloric intake in two experimental groups. The mice in two control groups received the same procedures as above, except for burn injury. On day 7 after injury, all mice among four groups were euthanized and the entire intestine was harvested. Intestinal immunoglobulin A (IgA) levels, total lymphocyte yield, and lymphocyte subpopulations in Peyer's patches were analyzed. Levels of IFN-gamma, IL-2, IL-4 and IL-10 in gut homogenates were also measured by ELISA. Total lymphocyte yield, numbers of lymphocyte subpopulations, and intestinal IgA levels in the EN+ARG group were higher than those in the EN group (p<0.05). Levels of gut tissue cytokines were significantly altered with enteral Arg supplementation: levels of IL-4 and IL-10 were increased, and levels of IFN-gamma and IL-2 declined, when compared with the EN-fed mice (p<0.05). The results of this study suggested that enteral nutrition supplemented with Arg has changed the cytokine concentrations in intestinal homogenates from a pro- to an anti-inflammatory profile, increased sIgA levels and changed lymphocytes in severely burned mice.

The influence of Peyer's patch apoptosis on intestinal mucosal immunity in burned mice

The aim of this study was to investigate the influence of apoptosis on Peyer's patches and the intestinal immunoglobulin A (IgA) response in burned mice. Sixty male Balb/c mice were randomly assigned into the sham-burn (control) group ( n = 30) and the burn group ( n = 30). The mice in the burn group received a full-thickness scald burn over 20% of the total body surface area (TBSA), on the back. At 12, 24 and 72 h, respectively, after injury, the burned mice ( n = 10, at every time point) were anaesthetised and their entire intestines were collected. The mice in the sham-burn group were treated with the same procedure as above, except for the burn injury. The number of Peyer's patches on every entire intestine and the total Peyer's patches cell yield were counted. The changes of lymphocyte subpopulations in Peyer's patches were measured by flow cytometry (FCM). And the levels of intestinal IgA were examined by enzyme-linked immunosorbent assay (ELISA). Fluoresceinisothiocyanate (FITC)-conjugated Annexin-τ and propiddium iodide (PI) double-staining cells were analysed by FCM for apoptotic ratio in Peyer's patches. The results showed that the total Peyer's patch cell yield and the numbers of CD3, CD4, CD8 and CD19 cells were significantly decreased at 12, 24 and 72 h after injury ( P < 0.05), and that the intestinal IgA levels were markedly reduced at 24 and 72 h ( P < 0.05). On the other hand, total apoptotic ratio and all cell subpopulation apoptosis in Peyer's patches were dramatically increased at 12, 24 and 72 h after injury ( P < 0.05). These results indicated that severe burns led to a significant decrease in the number of Peyer's patch cells and in intestinal IgA levels, which was closely associated with strongly increased apoptosis in Peyer's patches.

Effects of enteral nutrition supplemented with glutamine on intestinal mucosal immunity in burned mice

Objective The aim of this study was to investigate the effects of enteral nutrition (EN) supplemented with glutamine (GLN) on Peyer's patches and intestinal immunoglobulin A (IgA) response in burned mice. Methods Thirty-four mice were randomly assigned to a normal control group ( n = 10), an EN group (n = 12), and an EN supplemented with GLN (EN + GLN) group (n = 12) and mice in the EN and EN + GLN groups received a 20% total body surface area, full-thickness scald burn on the back. Then the burned mice were fed with conventional EN or EN + GLN for 7 d. There was isonitrogenous and isocaloric intake in the EN and EN + GLN groups. On day 7 after injury, entire intestines were collected and intestinal IgA levels, total lymphocyte yield, lymphocyte subpopulations, and total apoptotic ratio in Peyer's patches were analyzed. Results Total lymphocyte yield, numbers of lymphocyte subpopulations, and intestinal IgA levels in the EN + GLN group were significantly higher than those in the EN group ( P < 0.05). The total apoptotic ratio in Peyer's patches was markedly decreased in the EN + GLN group compared with that in the EN group ( P < 0.05). Conclusion The results indicated that EN supplemented with GLN is superior to conventional EN with respect to improvement of intestinal immunity in burned mice.

Influence of Adding Fish Oil to Parenteral Nutrition on Gut‐Associated Lymphoid Tissue

Lack of enteral nutrition reduces gut-associated lymphoid tissue (GALT) mass and function, a mechanism underlying the increased morbidity of infectious complications in severely injured or critically ill patients. Strategies to restore parenteral nutrition (PN)-induced changes of GALT mass and function have been pursued. However, the influences of adding fish oil to PN on gut immunity remain to be clarified. Male Institute of Cancer Research (ICR) mice (n = 50) were randomized to 4 groups: ad libitum chow (chow), fat free PN (fat (-)-PN), PN + fish oil (FO-PN), and PN + safflower oil (SO-PN). The PN groups were given isocaloric and isonitrogenous PN solutions. The FO- and SO-PN groups received 20% of total calories from fat emulsions. After 5 days of feeding, lymphocytes from Peyer's patches (PPs), the intraepithelial space (IE), and the lamina propria (LP) of the entire small intestine were isolated. GALT lymphocyte numbers and phenotypes (CD4+, CD8+, alphabetaTCR+, gammadeltaTCR+, B220+ cells) were determined. Immunoglobulin A (IgA) levels of small intestinal washings were also measured by enzyme-linked immunosorbent assay. Another set of mice (n = 24) was used to determine plasma fatty acid compositions after feeding. Lymphocyte numbers from PPs and the LP and intestinal IgA levels were significantly lower in the PN groups than in the chow group, with no significant differences between any 2 PN groups. The FO- and SO-PN groups showed moderate recovery of IE cell numbers compared with the fat (-)-PN group. Omega-3 and omega-6 fatty acid levels were increased with fish and safflower oil additions, respectively, compared with the fat (-)-PN group. Adding fish oil to PN does not exacerbate PN-induced GALT changes but rather partially reverses these changes, with increased plasma omega-3 fatty acid levels.

Intestinal Polymeric Immunoglobulin Receptor Is Affected by Type and Route of Nutrition

Secretory immunoglobulin A (SIgA) prevents adherence of pathogens at mucosal surfaces to prevent invasive infection. Polymeric immunoglobulin receptor (pIgR) is located on the basolateral surface of epithelial cells and binds dimeric immunoglobulin A (IgA) produced by plasma cells in the lamina propria. This IgA-pIgR complex is transported apically, where IgA is exocytosed as SIgA to the mucosal surface. Our prior work shows that mice fed intragastric (IG, an elemental diet model) and IV parenteral nutrition (PN) solution have reduced intestinal T and B cells, SIgA, and interleukin-4 (IL-4) compared with mice fed chow or a complex enteral diet (CED). Prior work also demonstrates a reduction in IgA transport to mucosal surfaces in IV PN-fed mice. Because IL-4 up-regulates pIgR production, this work studies the effects of these diets on intestinal pIgR. Male Institute of Cancer Research (ICR) mice were randomized to chow (n = 11) with IV catheter, CED (n = 10) or IG PN (n = 11) via gastrostomy and IV PN (n = 12) for 5 days. CED and PN were isocaloric and isonitrogenous. Small intestine was harvested for pIgR and IL-4 assays after mucosal washing for IgA. IgA and IL-4 levels were analyzed by enzyme-linked immunosorbent assay and pIgR by Western blot. Small intestinal pIgR expression, IgA levels, and IL-4 levels decreased significantly in IV PN and IG PN groups. Lack of enteral stimulation affects multiple mechanisms responsible for decreased intestinal SIgA levels, including reduced T and B cells in the lamina propria, reduced Th-2 IgA-stimulating cytokines, and impaired expression of the IgA transport protein, pIgR.

Interleukin‐7 Dose‐Dependently Restores Parenteral Nutrition–Induced Gut‐Associated Lymphoid Tissue Cell Loss but Does Not Improve Intestinal Immunoglobulin A Levels

Without enteral nutrition, the mass and function of gut-associated lymphoid tissue (GALT), a center of systemic mucosal immunity, are reduced. Therefore, new therapeutic methods, designed to preserve mucosal immunity during parenteral nutrition (PN), are needed. Our recent study revealed that exogenous interleukin-7 (IL-7; 1 microg/kg twice a day) restores the GALT cell mass lost during intravenous (IV) PN but does not improve secretory immunoglobulin A (IgA) levels. Herein, we studied the IL-7 dose response to determine the optimal IL-7 dose for recovery of GALT mass and function during IV PN. We hypothesized that a high dose of IL-7 would increase intestinal IgA levels, as well as GALT cell numbers. Male mice (n = 42) were randomized to chow, IL-7-0, IL-7-0.1, IL-7-0.33, IL-7-1 and IL-7-3.3 groups and underwent jugular vein catheter insertion. The IL-7 groups were fed a standard PN solution and received IV injections of normal saline (IL-7-0), 0.1, 0.33, 1, or 3.3 microg/kg of IL-7 twice a day. The chow group was fed chow ad libitum. After 5 days of treatment, the entire small intestine was harvested and lymphocytes were isolated from Peyer's patches (PPs), intraepithelial (IE) spaces, and the lamina propria (LP). The lymphocytes were counted and phenotypes determined by flow cytometry (alphabetaTCR, gammadeltaTCR, CD4, CD8, B cell). IgA levels of small intestinal washings were also examined using ELISA (enzyme-linked immunoabsorbent assay). IL-7 dose-dependently increased total lymphocyte numbers in PPs and the LP. The number of lymphocytes harvested from IE spaces reached a plateau at 1 microg/kg of IL-7. There were no significant differences in any phenotype percentages at any GALT sites among the groups. IgA levels of intestinal washings were significantly higher in the chow group than in any of the IL-7 groups, with similar levels in all IL-7 groups. Exogenous IL-7 dose-dependently reverses PN-induced GALT cell loss, with no major changes in small intestinal IgA levels. IL-7 treatment during PN appears to have beneficial effects on gut immunity, but other therapeutic methods are needed to restore secretory IgA levels.

5‐Fluorouracil Infusion Reduces Gut‐Associated Lymphoid Tissue Cell Number and Mucosal Immunoglobulin A Levels

Anticancer drugs have been demonstrated to affect gut mucosal morphology and cause gastrointestinal symptoms. We hypothesized that even small doses of 5-fluorouracil (5-FU) would reduce gut-associated lymphoid tissue (GALT) mass and function. Mice underwent IV cannulation and received continuous infusion of normal saline or 10 mg/kg of 5-FU for 5 days. GALT cell numbers, phenotypes, and mucosal immunoglobulin A (IgA) levels were measured. During the infusion, there were no significant differences in food intake or body weight change between the 2 groups. Cell yields from the intraepithelial space and lamina propria of the small intestine were lower in the 5-FU than the control group. The lamina propria CD4/CD8 ratio was reduced in the 5-FU compared with the control group. Intestinal and respiratory tract IgA levels were lower in the 5-FU than in the control group. A small dose of 5-FU reduces GALT cell number and mucosal IgA levels, regardless of food intake.

The C‐Terminal Heptapeptide of Bombesin Reduces the Deleterious Effect of Total Parenteral Nutrition (TPN) on Gut‐Associated Lymphoid Tissue (GALT) Mass but Not Intestinal Immunoglobulin A In Vivo

Background: Bombesin, the amphibian analog of mammalian gastrin‐releasing peptide, reverses total parenteral nutrition (TPN)–induced atrophy of gut‐associated lymphoid tissue and increases intestinal and respiratory immunoglobulin A (IgA) levels. Structure‐activity studies suggested that the biologically active portion of bombesin is a C‐terminal heptapeptide (7AA). This study investigates the effect of 7AA on lymphocytes counts of the Peyer's patches (PP), the lamina propria (LP) and the intraepithelial layer (IE). Methods: Forty‐eight male mice were randomized to receive chow (n = 13), TPN only (n = 9), TPN + 15 μg 7AA 3 times per day (n = 13) or TPN + 150 μg 7AA 3 times per day (n = 13). After 5 days of feeding, PP, LP, and IE lymphocytes were determined. Intestinal IgA levels were measured with ELISA. Groups were compared with ANOVA. Results: All TPN‐fed mice lost more weight than mice fed chow (p &lt; .04). Lymphocyte counts in PP, LP, and IE were significantly lower in the TPN group than in the 3 other groups but did not differ between the groups fed chow, TPN + 15 μg 7AA 3 times per day, or TPN + 150 μg 7AA 3 times per day. Intestinal IgA levels were higher in chow‐fed mice (148.4± 16.9) than in mice fed TPN (98.4 ± 14.0, p = .008), TPN + 15 μg 7AA 3 times per day (96.9 ± 7.7, p = .003) or TPN + 150 μg 7AA 3 times per day (87.3 ± 6.7, p = .001). Conclusions: The C‐terminal heptapeptide of bombesin prevented the TPN‐induced decrease in intestinal lymphocyte populations but not the reduction in intestinal IgA levels.

Individual Neuropeptides Regulate Gut‐Associated Lymphoid Tissue Integrity, Intestinal Immunoglobulin A Levels, and Respiratory Antibacterial Immunity

Total parenteral nutrition (TPN) leads to atrophy of the gut-associated lymphoid tissue (GALT) and a significant decrease in intestinal immunoglobulin A (IgA) levels, a major constituent of mucosal immunity. Bombesin (BBS) prevents TPN-induced GALT atrophy and maintains intestinal IgA levels. BBS, a neuropeptide analogous to gastrin-releasing peptide in humans, stimulates the release of other gut neuropeptides including cholecystokinin (CCK), gastrin, and neurotensin (NT). This study investigates the ability of CCK, gastrin, or NT to individually prevent TPN-induced GALT atrophy and preserve respiratory immunity. Experiment 1: Male mice were randomly assigned to receive chow, TPN, TPN plus CCK, TPN plus gastrin, or TPN plus NT. After 5 days of feeding, Peyer's patches (PP) from the proximal and distal small bowel were harvested and analyzed for cell yields. PP cells were also analyzed for GALT cell type. Small bowel IgA levels were measured by enzyme-linked immunosorbent assay (ELISA). Experiment 2: Mice were randomly assigned to receive either liposomes containing Pseudomonas antigen or liposomes without antigen. After 10 days, mice were randomly assigned to the same five treatment groups, fed for 5 days, and then given intratracheal Pseudomonas. Mortality was assessed after 48 hours. Experiment 1: GALT cell reductions due to IV-TPN were greater in the distal than proximal small bowel. All three neuropeptides prevented most TPN-induced GALT atrophy due mainly to the maintenance of the B-cell and T-cell populations in the PP of the distal bowel. Intestinal IgA levels were significantly higher in the animals treated with neuropeptides than animals treated with TPN only; however, these IgA levels were not maintained at levels observed in chow-fed animals. Experiment 2: Immunization resulted in significantly lower mortality in animals fed chow, TPN plus CCK, and TPN plus gastrin. TPN alone and TPN plus NT resulted in loss of immunity and mortality rate at comparable levels to unimmunized animals. Supplementation of IV-TPN with CCK, gastrin, and NT prevents GALT atrophy, primarily in the distal bowel. Intestinal IgA levels improve but not to normal levels. CCK and gastrin reversed IV-TPN-induced effects on antibacterial pneumonia in immunized animals while NT did not.