L-arginine-enriched parenteral nutrition affects lymphocyte phenotypes of gut-associated lymphoid tissue

BACKGROUND: Experimentally, total parenteral nutrition (TPN) diminishes gut-associated lymphoid tissue (GALT) cell numbers and function. Although glutamine supplementation is known to reverse TPN-induced changes in GALT, effects of another conditionally essential amino acid, L-arginine (ARG), on GALT remain unclear. METHODS: Twenty-two male Institute of Cancer Research mice were randomized to standard TPN (0.3% arginine, STD-total parenteral nutrition) or 1% ARG-enriched TPN (ARG-total parenteral nutrition). After 5 days of feeding, lymphocytes were harvested from Peyer's patches (PP), the lamina propria, and intraepithelial (IE) spaces of the small intestine to determine cell yields. Lymphocyte phenotypes (alphabetaTCR, gammadeltaTCR, CD4, CD8, and B220 as a B cell marker) were determined using flow cytometry. IgA levels in washings of the small intestine, upper respiratory tract, and lungs were measured with ELISA. RESULTS: ARG-total parenteral nutrition did not affect lymphocyte yields. The percentages of CD4+ cells in PP and IE, and alphabetaTCR+ cells in PP, were significantly higher in the ARG-total parenteral nutrition than in the STD-total parenteral nutrition mice, without marked differences in other phenotypes examined. There were no significant differences in intestinal and respiratory tract IgA levels between the 2 groups of mice. CONCLUSIONS: One percent ARG supplementation of TPN does not improve GALT cell number or mucosal IgA level but benefits to increase CD4+ cell percentages in GALT.     

Interleukin-7 dose-dependently restores parenteral nutrition-induced gut-associated lymphoid tissue cell loss but does not improve intestinal immunoglobulin a levels

BACKGROUND: 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. METHODS: 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). RESULTS: 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. CONCLUSIONS: 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.     

An investigation into the effect of a probiotic on gut immune function in surgical patients

BACKGROUND: The gut-associated lymphoid tissue (GALT) is an important component of the gut barrier. We have previously demonstrated a significant increase in various parameters of gut immune function in association with bacterial translocation. Animal studies have suggested that the probiotic Lactobacillus plantarum 299v improves the immunological status of the intestinal mucosa. The aim of this study was to determine whether the same is true in humans. METHOD: This was a prospective randomised controlled study, in which immunohistochemical techniques were used to measure the concentrations of plasma cells, IgA positive cells and IgM positive cells in the lamina propria, together with the concentrations of IgA and IgM at the mucosal surface in specimens of normal small bowel obtained from patients undergoing elective abdominal surgery who had consumed an oral preparation containing the probiotic Lactobacillus plantarum 299v (ProViva) during the immediate preoperative period. These were compared with similar specimens obtained from control subjects who did not receive the probiotic. RESULTS: A total of 22 patients were studied (probiotic group n = 11, control group n = 11). The median volume of ProViva consumed was 3250 ml (range 2100-9000 ml), for a median duration of 9 days (range 5-18 days). There were no significant differences between the probiotic and control groups in terms of concentrations of plasma cells, IgA positive cells or IgM positive cells in the lamina propria. There was a significantly higher concentration of IgM at the mucosal surface in the control group (P = 0.02, Fishers Exact test mid P), but no difference in terms of IgA. CONCLUSIONS: The increase in IgA observed in the intestinal mucosa in response to probiotics in animal studies does not occur in humans. The significance of the increase in IgM at the mucosal surface in the controls is unclear.     

Influence of adding fish oil to parenteral nutrition on gut-associated lymphoid tissue

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.     

Albumin infusion after reperfusion prevents gut ischemia-reperfusion-induced gut-associated lymphoid tissue atrophy

BACKGROUND: Our recent study clarified that gut ischemia-reperfusion (I/R) causes gut-associated lymphoid tissue (GALT) mass atrophy, a possible mechanism for increased morbidity of infectious complications after severe surgical insults. Because albumin administration reportedly reduces hemorrhagic shock-induced lung injury, we hypothesized that albumin treatment prevents GALT atrophy due to gut I/R. METHODS: Male mice (n = 37) were randomized to albumin, normal saline, and sham groups. All groups underwent jugular vein catheter insertion. The albumin and normal saline groups underwent 75-minute occlusion of the superior mesenteric artery. During gut ischemia, all mice received normal saline infusions at 1.0 mL/h. The albumin group was given 5% bovine serum albumin in normal saline at 1.0 mL/h for 60 minutes after reperfusion, whereas the normal saline group received 0.9% sodium chloride at 1.0 mL/h. The sham group underwent laparotomy only. Mice were killed on day 1 or 7, and the entire small intestine was harvested. GALT lymphocytes were isolated and counted. Their phenotypes (alphabetaTCR, gammadeltaTCR, CD4, CD8, B220) were determined by flow cytometry. RESULTS: On day 1, the gut I/R groups showed significantly lower total lymphocyte and B cell numbers in Peyer's patches and the lamina propria than the sham group. However, the albumin infusion partially but significantly restored these cell numbers. On day 7, there were no significant differences in any of the parameters measured among the 3 groups. CONCLUSIONS: Albumin infusion after a gut ischemic insult may maintain gut immunity by preventing GALT atrophy.     

Effects of adding butyric acid to PN on gut-associated lymphoid tissue and mucosal immunoglobulin A levels

Background: 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. Methods: 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. Results: 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. Conclusions: A new PN formula containing butyric acid is feasible and would ameliorate PN‐induced impairment of mucosal immunity.     

Influence of adding pyrroloquinoline quinone to parenteral nutrition on gut-associated lymphoid tissue

Background: Experimental intravenous (IV) parenteral nutrition (PN) diminishes gut‐associated lymphoid tissue (GALT) cell number and function. PN solution cannot maintain GALT at the same level as a normal diet, even when delivered intragastrically (IG). Previous studies demonstrated pyrroloquinoline quinone (PQQ)–deficient mice to be less immunologically responsive. Because standard (STD) PN solution lacks PQQ, PQQ supplementation may prevent PN‐induced GALT changes. This study was designed to determine the influence of adding PQQ to PN on GALT. Methods: In experiment 1, mice (n = 32) were randomized to chow, IV‐STD‐PN, and IV‐PQQ‐PN groups. The chow group was fed chow with the same caloric content as PN. The IV‐STD‐PN group received STD‐PN solution, whereas the IV‐PQQ‐PN group was given PQQ (3 mcg/d)–enriched PN by the IV route. After 5 days of feeding, lymphocytes were isolated from the Peyer's patch (PPs), intraepithelial space (IE), and lamina propria (LP) of the small intestine. GALT lymphocyte number and phenotype (αβTCR+, γδTCR+, CD4+, CD8+, B220+ cells) and intestinal immunoglobulin A (IgA) level were determined. In experiment 2, mice (n = 28) were randomized to IG‐STD‐PN or IG‐PQQ‐PN group. After IG nutrition supports, GALT mass and function were determined as in experiment 1. Results: The IV‐PQQ‐PN group showed increased PP lymphocyte number and PP CD8+ cell number compared with the IV‐STD PN group. The IG‐PQQ‐PN group had significantly greater PP lymphocyte number and PP CD4+ cell numbers than the IG‐STD‐PN group. Neither IV nor IG PQQ treatment raised IgA level. Conclusions: PQQ added to PN partly restores GALT mass, although its effects on GALT function remain unclear.     

Individual neuropeptides regulate gut-associated lymphoid tissue integrity, intestinal immunoglobulin A levels, and respiratory antibacterial immunity

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.     

Bovine whey protein concentrate supplementation modulates maturation of immune system in suckling rats

During neonatal life, challenges from breast milk and microbial flora promote immune system maturation. Immunonutrition in these stages may become an important way to increase natural defence systems. The aim of this study was to determine the effect of a daily bovine milk whey protein concentrate (WPC) supplement on the intestinal and systemic immune systems in suckling rats. The composition of intraepithelial and lamina propria lymphocytes (IEL and LPL) was analysed by flow cytometry. Systemic and intestinal humoral immune responses were determined by sera Ig levels and Ig-secreting cell quantification by ELISA and ELISPOT, respectively. From birth, suckling Wistar rats were supplemented with WPC or standard infant formula (SIF). The WPC group showed the same proportion of most of the main mucosal cell subsets as the reference animals. However, in the first days of life WPC enhanced the innate immunity by increasing the NK cell proportion in both epithelial and lamina propria (LP) compartments. A rise in intestinal CD8alphaalpha+ IEL was also induced by WPC supplementation. A time-course of sera Ig levels and spontaneous IgA, IgM and IgG production by LPL and mononuclear cells from blood and spleen, in the WPC group, exhibited a similar pattern to those pups fed only by dam's milk. In summary, the present results show the effects of WPC on enhancing mucosal innate immunity during early life.     

Intestinal polymeric immunoglobulin receptor is affected by type and route of nutrition

BACKGROUND: 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. METHODS: 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. RESULTS: Small intestinal pIgR expression, IgA levels, and IL-4 levels decreased significantly in IV PN and IG PN groups. CONCLUSIONS: 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.     

Influences of Short‐Term Fasting and Carbohydrate Supplementation on Gut Immunity and Mucosal Morphology in Mice

Background: Preoperative carbohydrate (CHO) supplementation has been recommended in enhanced recovery after surgery protocols. However, the effects of CHO supplementation on gut and systemic immunity are not well understood. Methods: Mice (n = 60) were randomized to 1 of the following 5 groups: control (ad lib feeding), 12‐hour fasting without CHO administration (fasting), and 12 hours of fasting with CHO administration at 2, 4, and 8 hours before sacrifice. Then, lymphocytes were isolated from gut‐associated lymphoid tissue, that is, Peyer's patches, the intraepithelial space, and the lamina propria of the small intestine. These lymphocyte numbers and phenotypes were evaluated. IgA levels in respiratory and small‐intestinal washings were determined by ELISA. Morphology, proliferation, and apoptosis of the intestinal epithelium were also evaluated histologically. Results: Although there were no significant differences in IgA levels among the 5 groups, fasting decreased intraepithelial and lamina propria, but not Peyer's patches lymphocyte numbers. CHO at 2 hours prevented lymphocyte loss in intraepithelial, whereas CHO at 4 hours reversed lamina propria lymphocytes numbers. Percentages of lymphocyte phenotypes were similar in each site among the 5 groups. Fasting caused villous atrophy; however, CHO at 2 hours restored villous structure along with maintenance of epithelial cell proliferation rate. Conclusions: Only 12 hours of fasting causes marked gut‐associated lymphoid tissue cell loss along with gut atrophy. However, CHO at 2 hours preserves gut immunity and morphology not completely but moderately.     

Influences of long-term antibiotic administration on Peyer's patch lymphocytes and mucosal immunoglobulin A levels in a mouse model

BACKGROUND: Long-term antibiotic administration is sometimes necessary to control bacterial infections during the perioperative period. However, antibiotic administration may alter gut bacterial flora, possibly impairing gut mucosal immunity. We hypothesized that 1 week of subcutaneous (SC) antibiotic injections would affect Peyer's patch (PP) lymphocyte numbers and phenotypes, as well as mucosal immunoglobulin A (IgA) levels. METHODS: Sixty-one male Institute of Cancer Research mice were randomized to CMZ (cefmetazole 100 mg/kg, administered SC twice a day), IPM (imipenem/cilastatin 50 mg/kg x 2), and control (saline 0.1 mL x 2) groups. After 7 days of treatment, the mice were killed and their small intestines removed. Bacterial numbers in the small intestine were determined using sheep blood agar plates under aerobic conditions (n = 21). PP lymphocytes were isolated to determine cell numbers and phenotypes (CD4, CD8, alphabetaTCR, gammadeltaTCR, B220; n = 40). IgA levels in the small intestinal and bronchoalveolar washings were also measured with ELISA. RESULTS: Antibiotic administration decreased both bacterial number and the PP cell yield compared with the control group. There were no significant differences in either phenotype percentages or IgA levels at any mucosal sites among the 3 groups. CONCLUSIONS: Long-term antibiotic treatment reduces PP cell numbers while decreasing bacterial numbers in the small intestine. It may be important to recognize changes in gut mucosal immunity during long-term antibiotic administration.     

Expression of interleukin-4, interferon-gamma and lymphocyte surface markers in small intestinal mucosa of adult patients with cereal allergy

INTRODUCTION: The mechanism for adverse reactions to foods in the gastrointestinal tract are poorly understood. Previous studies of other atopic diseases and animal models suggest that lymphocytes and cytokines may be implicated in the pathogenesis of food allergy. AIM: The authors investigated the expression of interleukin-4, interferon-gamma and other lymphocyte markers of patients with cereal allergy (wheat, rye, oats) and of controls. PATIENTS/METHOD: Expressions of cytokines and lymphocyte markers on duodenal mucosa of nine patients (mean age 38.3 years, range 18-50 years, 8 women and one man) and nine controls (mean age 36 years, range 24-54 years, 6 women, 3 men) by means of immunohistochemistry were investigated. RESULTS: The mucosal structure on every biopsy specimens was normal. Despite the normal structure the expression of Ki-67 intranuclear proliferation marker was higher in patients with cereal allergy. Expression of interleukin-4 was markedly elevated in the food allergy group, however, interferon-gamma density showed no inter-group difference. The densities of CD4 (1251 vs. 1053 cells/mm2) and HLA-DR positive cells (1227 vs. 1064 cells/mm2) in the lamina propria of cereal allergy group were significantly elevated when compared with controls (P = 0.05 and P = 0.04, respectively). The densities of CD3, CD8, TCR alpha/beta and gamma/delta, HLA-DP, IgA, IgA1, IgA2-containing cells did not differ in the two groups studied. CONCLUSIONS: The authors results suggest that, despite the normal mucosal structure, the increased expression of CD4 and HLA-DR positive cells show a sign of inflammation in duodenal biopsies of patients with cereal allergy. Moreover, increased density of IL-4 may suggest its role in the pathogenesis of cereal hypersensitivity.     

Breakdown of mucosal immunity in gut by 2,3,7,8-tetraclorodibenzo-p-dioxin (TCDD)

Objectives Mucosal immunity plays a pivotal role for body defense against infection and allergy. The aim of this study was to clarify the effects of 2,3,7,8-tetraclorodibenzo-p-dioxin (TCDD) on mucosal immunity in the gut. Methods Fecal IgA level and oral tolerance induction were examined in TCDD-treated mice. Flow cytometric and histological analyses were also performed. Results Single oral administration of low dose 2,3,7,8-TCDD resulted in a marked decrease in IgA secretion in the gut without any effects on the cellular components of gut-associated lymphoid tissues (GALT) including Peyer’s patches (PPs) and mesenteric lymph nodes (LNs). Decressed IgA secretion by TCDD was not observed in aryl hydrocarbon receptor (AhR)-deficient mice. Flow cytometric analysis revealed that IgA B cells in PPs and the mesenteric LNs remained unchanged in the TCDD-treated mice. An immunofluorescence study also demonstrated that a significant number of cytoplasmic IgA cells were present in the lamina propria of the gut in the TCDD-treated mice. Furthermore, oral tolerance induction by ovalbumin (OVA) was impaired in the TCDD-treated mice and OVA-specific T cell proliferation occurred in the peripheral lymphoid tissues including the spleen and LNs. Conclusions These results suggest that a relatively low dose of TCDD impairs mucosal immunity in the gut and induces systemic sensitization by oral antigens.     

Nutrition disorder and immunologic parameters: study of the intestinal villi in growing rats

OBJECTIVE: The aim of the present work was to study how a diet in which cereals were the only protein source would affect B and T lymphocytes and a cell population positive for thymus-expressed chemokine (TECK) in the intestinal villi of growing rats. METHODS: Wistar rats were fed a 6.5% precooked maize protein diet for 18-20 d (M group). An age-matched control group received stock diet (C group). Body weight (grams) was determined, ponderal growth rate (grams per day per 100 g) was calculated, and intestines were removed and processed by Saint-Marie's technique. Tissue sections were studied by indirect immunofluorescence. CD5(+) T cells and the T-cell subsets TCRalphabeta(+), TCRgammadelta(+), CD4(+), CD8alpha(+), and CD8beta(+) in the lamina propria (LP) and intraepithelium, in addition to immunoglobulin A-positive B cells in the LP were determined (n cells/30 fields were read). In addition, the presence of the TECK(+) cell population was qualitatively assessed. RESULTS: The M versus C group showed statistically significant differences in body weight and ponderal growth rate. The number of immunoglobulin A-positive B cells in the LP and the CD5(+) T cells and CD4(+), CD8alpha(+), CD8beta(+), TCRalphabeta(+), and TCRgammadelta(+) T-cell subpopulations of the M group in the LP and intraepithelium of the gut villi were significantly decreased compared with the C group (P < 0.001). The M group also showed differences in the size and cellularity of the gut villi and in the distribution of TECK. CONCLUSION: The results show that intake of a low concentration of a low-quality dietary protein as the only source of protein produces an important disorder in the mucosal immunity of experimental rats.     

Consumption of rice bran increases mucosal immunoglobulin A concentrations and numbers of intestinal Lactobacillus spp

Gut-associated lymphoid tissue maintains mucosal homeostasis by combating pathogens and inducing a state of hyporesponsiveness to food antigens and commensal bacteria. Dietary modulation of the intestinal immune environment represents a novel approach for enhancing protective responses against pathogens and inflammatory diseases. Dietary rice bran consists of bioactive components with disease-fighting properties. Therefore, we conducted a study to determine the effects of whole dietary rice bran intake on mucosal immune responses and beneficial gut microbes. Mice were fed a 10% rice bran diet for 28 days. Serum and fecal samples were collected throughout the study to assess total immunoglobulin A (IgA) concentrations. Tissue samples were collected for cellular immune phenotype analysis, and concentrations of native gut Lactobacillus spp. were enumerated in the fecal samples. We found that dietary rice bran induced an increase in total IgA locally and systemically. In addition, B lymphocytes in the Peyer's patches of mice fed rice bran displayed increased surface IgA expression compared with lymphocytes from control mice. Antigen-presenting cells were also influenced by rice bran, with a significant increase in myeloid dendritic cells residing in the lamina propria and mesenteric lymph nodes. Increased colonization of native Lactobacillus was observed in rice bran-fed mice compared with control mice. These findings suggest that rice bran-induced microbial changes may contribute to enhanced mucosal IgA responses, and we conclude that increased rice bran consumption represents a promising dietary intervention to modulate mucosal immunity for protection against enteric infections and induction of beneficial gut bacteria.     

Apoptosis of antigen-specific CTLs contributes to low immune response in gut-associated lymphoid tissue post vaccination

The gut-associated lymphoid tissue (GALT) represents a major reservoir of HIV in infected individuals. Vaccines can induce strong systemic immune responses but these have less impact on CD4 T cells activity and numbers in GALT. In this study, we vaccinated mice with an adenovirus vector that expressed the envelope gene from HIV and observed immune responses in the peripheral blood, spleen, liver, mesenteric lymph nodes, and Peyer's patches. We found that (1) the number of HIV-specific CD8 T cells was dramatically lower in GALT than in other tissues; (2) the programmed cell death protein-1 (PD-1) was expressed at high levels in HIV-specific CD8 T cells including memory T cells in GALT; and (3) high levels of HIV-specific CD8 T cell apoptosis were occurring in GALT. These results suggest that contributing to GALT becoming an HIV reservoir during infection is a combination of exhaustion and/or dysfunction of HIV-specific CTLs at that site. These results emphasize the importance of developing of an effective mucosal vaccine against HIV.     

Vitamin A prevents the decline in immunoglobulin A and Th2 cytokine levels in small intestinal mucosa of protein-malnourished mice

We examined whether vitamin A improved mucosal immune depression in mice with wasting protein deficiency. In male C3H/HeN mice fed a semi-purified 1% protein diet for 2 wk, plasma retinol and immunoglobulin A (IgA) concentrations in the small intestinal mucosa were 50 and 55%, respectively, of those in mice fed a semi-purified 20% protein diet, (P < 0.05). Daily supplementation of 0.3 mg of retinyl acetate to protein-deficient mice for 2 wk increased the plasma retinol level to the value in the protein-sufficient mice. However, 1 mg/d of retinyl acetate was required to prevent the decline of the IgA level caused by the protein deficiency. Mice fed the low-protein diet had lower concentrations of IL-4 and IL-5 in the small intestinal mucosa and fewer IL-4- and IL-5-containing cells in the lamina propria (P < 0. 05). Retinyl acetate (1 mg) significantly restored the IL-5 level and the number of IL-4- and IL-5-containing cells. After immunization with 20 microg of cholera toxin (CT), the intestinal mucosa of protein-deficient mice contained significantly less CT-specific IgA than control mice. Treatment with 1 mg of retinyl acetate prevented the decline of anti-CT IgA level in the protein-deficient mice, improving their survival rate after an exposure to 0.1 mg of CT. These results suggest that large oral supplements of vitamin A may preserve mucosal IgA level during protein malnutrition, possibly by stimulating Th2 cytokine production and thereby, inducing resistance against infection.     

Dietary plasma protein reduces small intestinal growth and lamina propria cell density in early weaned pigs

ABSTRACT We quantified the effects of a diet containing animal plasma protein on small intestinal growth and mucosal morphology in early weaned pigs. Ninety-six pigs [14 d old, 4 kg body weight (BW)] were assigned in groups of 32 to three dietary treatments as follows: 1) free access to control diet (C), 2) free access to plasma protein diet (P), and 3) plasma protein, pair-fed to C (PPF). Eight pigs from each group were killed at 2, 4, 8 or 16 d. Over a 16-d period, weight gain in the P group was 43% greater (P < 0.05) than that in C pigs; weight gain was similar in C and PPF groups. Protein intake in the P group was 33% higher (P < 0.05) than that in the PPF group; no significant difference was observed between the C and P groups. Dietary protein conversion efficiencies in both the P and PPF groups were approximately 18% greater (P < 0.05) than those in the C group. Intestinal masses in the three groups did not differ at 2, 4 and 8 d. By 16 d, the jejunal and ileal protein and DNA masses (mg/kg BW) in both the P and PPF groups were lower than those in the C group (P < 0.05). Dietary plasma protein did not affect crypt cell proliferation, crypt depth or villous height in either the jejunum or ileum. However, the intravillous lamina propria cell density in the jejunum was significantly lower (P < 0.05) in P and PPF pigs than in C pigs. Plasma urea concentrations were also 40 and 42% lower (P < 0.05) in the P and PPF groups, respectively, than in the C group. Our results indicate that dietary plasma protein reduces the cellularity of the lamina propria, but not epithelial cell surface of the small intestine. Feeding plasma protein also increased the efficiency of dietary protein utilization, in part, by decreasing amino acid catabolism.