The mucosa-associated lymphoid tissue structure, function, and derangements

Disease-Specific Expression of Conjunctiva Associated Lymphoid Tissue (CALT) in Mouse Models of Dry Eye Disease and Ocular Allergy

Conjunctiva-associated tissue (CALT) is assumed to play a crucial role in the immune system of the ocular surface. Its function in several ocular surface diseases (OSD) is still not fully understood. This study investigates the function of CALT in mouse models of dry-eye disease and ocular allergy. Since antigen-presentation is the central similarity in the pathologies, this study focuses on antigen-presentation in CALT Morphology and the expression of CALT, which was investigated in mice after induction of dry-eye, ocular allergy, topical antigen-stimulation, and after local depletion of phagocytic cells. Antigen uptake was investigated after the application of fluorescent ovalbumin (OVA). OSD influences the appearance and morphology of CALT in a disease-dependent manner. Ocular allergy leads to an increase and dry-eye disease to a decrease in number and size of CALT. The development of CALT is dependent on the presence of APCs. Professional APCs are present in CALT, and soluble antigen is transported into the follicle. CALT appearance is disease-specific and indicative of differing functions. Although the specific involvement of CALT in OSD needs further study, the existence of functional APCS and antigen-uptake supports the hypothesis that CALT is an immunological key player at the ocular surface.

Diet, Microbiota and Gut-Lung Connection

The gut microbial community (Gut microbiota) is known to impact metabolic functions as well as immune responses in our body. Diet plays an important role in determining the composition of the gut microbiota. Gut microbes help in assimilating dietary nutrients which are indigestible by humans. The metabolites produced by them not only modulate gastro-intestinal immunity, but also impact distal organs like lung and brain. Micro-aspiration of gut bacteria or movement of sensitized immune cells through lymph or bloodstream can also influence immune response of other organs. Dysbiosis in gut microbiota has been implicated in several lung diseases, including allergy, asthma and cystic fibrosis. The bi-directional cross-talk between gut and lung (termed as Gut-Lung axis) is best exemplified by intestinal disturbances observed in lung diseases. Some of the existing probiotics show beneficial effects on lung health. A deeper understanding of the gut microbiome which comprises of all the genetic material within the gut microbiota and its role in respiratory disorders is likely to help in designing appropriate probiotic cocktails for therapeutic applications.

Effect of hypocaloric normoprotein or trophic feeding versus target full enteral feeding on patient outcomes in critically ill adults: a systematic review

Uncertainty surrounds the optimal approach to feeding the critically ill, with increasing interest in the concept of intentional underfeeding to reduce metabolic stress while maintaining gut integrity. Conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, this systematic review evaluates clinical outcomes reported in studies comparing hypocaloric normonitrogenous or trophic feeding (collectively 'intentional underfeeding') targeted full energy feeding administered via enteral nutrition to adult critically ill patients. Electronic databases including PubMed, CINAHL, EMBASE and CENTRAL were searched up to September 2017 for trials evaluating intentional underfeeding versus targeted energy feeding interventions on clinical outcomes (mortality, length of stay, duration of ventilation, infective complications, feeding intolerance and glycaemic control) among critically ill adult patients. Bias of included studies was assessed using the Cochrane risk of bias tool. Of the 595 articles identified, seven studies (six randomised controlled trials, one non-randomised trial) met the inclusion criteria, representing 2,684 patients (hypocaloric normonitrogenous n=668; trophic n=681; full energy feeding n=1335). Across the studies, there was considerable heterogeneity in study methodology, population, feeding strategy and outcomes and their timepoints. We observed no evidence that intentional underfeeding, when compared to targeting full energy feeding, reduced mortality or duration of ventilation or length of stay. However, limited trial evidence is available on the impact of intentional underfeeding on post-discharge functional and quality of life outcomes.

IL-25 improves luminal innate immunity and barrier function during parenteral nutrition

BACKGROUND

Parenteral nutrition (PN) increases risks of infections in critically injured patients. Recently, PN was shown to reduce intestine luminal levels of the Paneth cell antimicrobial molecule secretory phospholipase A2 (sPLA2) and the goblet cell glycoprotein mucin2 (MUC2). These molecules are critical factors for innate mucosal immunity and provide barrier protection. Interleukin-4 (IL-4) and IL-13 regulate sPLA2 and MUC2 production through the IL-13 receptor. Because IL-25 stimulates IL-4 and IL-13 release and PN reduces luminal sPLA2 and MUC2, we hypothesized that adding IL-25 to PN would restore these innate immune factors and maintain barrier function.

METHODS

Two days after venous cannulation, male ICR (Institute of Cancer Research) mice were randomized to receive chow (n = 12), PN (n = 9), or PN + 0.7 μg of exogenous IL-25 (n = 11) daily for 5 days. Small-intestine wash fluid (SIWF) was collected for analysis of sPLA2 activity, MUC2 density, and luminal levels of IL-4 and IL-13. Small-intestinal tissue was harvested for analysis of tissue sPLA2 activity or immediate use in an ex-vivo intestinal segment culture (EVISC) to assess susceptibility of the tissue segments to enteroinvasive Escherichia coli.

RESULTS

PN reduced luminal sPLA2 (P < 0.0001) and MUC2 (P <0.002) compared with chow, whereas the addition of IL-25 to PN increased luminal sPLA2 (P < 0.0001) and MUC2 (P < 0.02) compared with PN. Tissue IL-4 and IL-13 decreased with PN compared with chow (IL-4: P < 0.0001, IL-13: P < 0.002), whereas IL-25 increased both cytokines compared with PN (IL-4: P < 0.03, IL-13: P < 0.02). Tissue levels of sPLA2 were significantly decreased with PN compared with chow, whereas IL-25 significantly increased tissue sPLA2 levels compared with PN alone. Functionally, more bacteria invaded the PN-treated tissue compared with chow (P < 0.01), and the addition of IL-25 to PN decreased enteroinvasion to chow levels (P < 0.01).

CONCLUSIONS

PN impairs innate mucosal immunity by suppressing luminal sPLA2 activity and MUC2 density compared with chow. PN also increases bacterial invasion in ex-vivo tissue. Administration of exogenous IL-25 reverses this dysfunction and increases luminal sPLA2 and MUC2. PN tissue treated with IL-25 was significantly more resistant to bacterial invasion than with PN alone, suggesting that IL-25-induced effects augment the barrier defense mechanisms.

JAK-STAT and intestinal mucosal immunology

The intestinal mucosal immune system is challenged with bacteria, viruses, and parasites, in addition to food and environmental antigens, that require dynamic immune responsiveness for homeostasis. One central signaling pathway is JAK-STAT, which regulates the adaptive and innate immune arms of mucosal immunity as well as epithelial repair and regeneration. Adaptive immunity includes lymphocyte mediated secretion of specific antibodies, while innate immune respones include secretion of non-antigen specific compounds. This review examines effects of specialized nutrition support on JAK-STAT in innate immune function and in lymphocyte modulation and epithelial antibody transport in gut-associated lymphoid tissue.

Enteral feeding in the critically ill: the role of the gastroenterologist

Expertise in enteral nutrition (EN) is an important aspect of the skill set of the clinical gastroenterologist. Delivery of adequate EN in critically ill patients is an active therapy that attenuates the metabolic response to stress and favorably modulates the immune system. EN is less expensive than parenteral nutrition and is favored in most cases because of improvement in patient outcomes, including infections and length of stay. Newer endoscopic techniques for placing nasoenteric feeding tubes have been developed, which improve placement success and efficiency. It appears that there is an ideal window period of 24-48 h when enteral feeding should be started in critically ill patients. Most patients can be fed into the stomach, but certain groups may benefit from small bowel feeding. Protocols on how to start and monitor enteral feeding have been developed. Immune-modulating feeding formulations also appear to be beneficial in specific patient populations. The gastroenterologist is a crucial member of the multidisciplinary team for nutritional support in the intensive care unit patient, with his knowledge of gastrointestinal pathophysiology, nutrition, and endoscopic feeding-tube placement.

Claude H. Organ, Jr. memorial lecture: splanchnic hypoperfusion provokes acute lung injury via a 5-lipoxygenase-dependent mechanism

Postinjury multiple organ failure (MOF) is the net result of a dysfunctional immune response to injury characterized by a hyperactive innate system and a suppressed adaptive system. Acute lung injury (ALI) is the first clinical manifestation of organ failure, followed by renal and hepatic dysfunction. Circulatory shock is integral in the early pathogenesis of MOF, and the gut has been invoked as the motor of MOF. Mesenteric lymph is recognized as the mechanistic link between splanchnic ischemia/reperfusion and distant organ dysfunction, but the specific mediators remain to be defined. Current evidence suggests the lipid fraction of postshock mesenteric lymph is central in the etiology of ALI. Specifically, our recent work suggests that intestinal phospholipase A2 generated arachidonic acid and its subsequent 5-lipoxygenase products are essential in the pathogenesis of ALI. Proteins conveyed via postshock mesenteric lymph also may have an important role. Elucidating these mediators and the timing of their participation in pulmonary inflammation is critical in translating our current knowledge to new therapeutic strategies at the bedside.

Ethanol Effects Proinflammatory State of Neutrophils in Shock

INTRODUCTION

Ethanol (EtOH) intoxication plays an important role in the etiology of traumatic events and has often been described as having immunosuppressive effects. EtOH has been shown to affect intestinal barrier function in prior studies. The ability of gut derived factors on neutrophil function in this setting is unknown. This study looks at the role of ethanol in modulating proinflammatory states in the neutrophil in vitro.

METHODS

Confluent Caco2 monolayers were exposed to 0.1% EtOH and/or Escherichia coli C-25 (EC) under normoxia (21% O(2)) or hypoxia (5% O(2)) followed by normoxic conditions (H/R). Neutrophils were then incubated with the supernatants from the treated cells. Chemotaxis, elastase and superoxide anion release, and CD11b measurements were undertaken in these neutrophils and compared with controls.

RESULTS

In the presence of EtOH, Caco2 cells undergoing H/R and bacterial challenge demonstrated a proinflammatory effect on neutrophils. The production of both elastase and superoxide anion were significantly increased from controls. Additionally, the presence of EtOH in Caco2 cells undergoing H/R with/without EC showed a statistically significant increase in CD11b expression and chemotaxis, when compared with controls.

CONCLUSIONS

EtOH has a proinflammatory role in the activation of neutrophils at the intestinal epithelial cell barrier in shock states. EtOH may play an important role in worsening septic complication in severely traumatized patients via dysregulation of neutrophils.

T-cell cytokines affect mucosal immunoglobulin A transport

BACKGROUND

Secretory immunoglobulin A (sIgA) is the principle immune defense against bacteria and other pathogens in the gut and other mucosal surfaces. sIgA is produced locally by plasma cells and transported (transcytosis) across epithelial cells into luminal secretions. sIgA production and transcytosis are governed by multiple signals, which may be affected by T cells. The purpose of this study was to elucidate the role of the Th1-type cytokine, interferon gamma (IFN-gamma), and the Th2-type cytokine interleukin-4 (IL-4) on IgA transcytosis across intestinal epithelial cells in vitro.

METHODS

HT-29 cell monolayers were established in a 2-chamber cell culture system. Cell monolayers were exposed to either IFN-gamma, IL-4, or both on the apical or basal side of the culture system systems for 48 hours. Dimeric IgA then was added to the basolateral chamber and transcytosis into the apical chamber was quantified by enzyme-linked immunosorbent assay at timed intervals. IgA transcytosis across HT-29 cells without prior addition of either cytokine served as a control.

RESULTS

Poly Ig-receptor up-regulation was shown by both IFN and IL-4. A combination of these 2 cytokines caused the greatest increase in receptor expression. A total of 3.7% of HT-29 cells expressed the polymeric Ig receptor in the control group. This increased to 23.7% in IL-4-treated cells, 66.3% in IFN-gamma-treated cells, and 71.5% of cells treated with both cytokines. These findings re-show previously published findings. The effects of IFN-gamma added to the basal chamber of HT-29 cell cultures shows a 7- to 10-fold increase in sIgA transcytosis at the 1-, 3-, and 12-hour time intervals. The effect of the addition of IL-4 to the basal chamber was similar to the results noted with IFN-gamma alone. The greatest IgA transcytosis was noted when IFN-gamma and IL-4 both were added to the basal chamber. However, these same results did not occur with cytokine exposure to the apical side of cell monolayers.

CONCLUSIONS

IFN-gamma and IL-4 increased IgA transport across HT-29 cells in a polar fashion. An increased effect on IgA transport was noted with the combination of IFN-gamma and IL-4. Delivery of T-cell cytokines to mucosal surfaces may support local antibody defense of mucosal surfaces and prevent infection.

BIOACTIVITY OF POSTSHOCK MESENTERIC LYMPH DEPENDS ON THE DEPTH AND DURATION OF HEMORRHAGIC SHOCK

Mesenteric hypoperfusion due to circulatory shock is a key event in the pathogenesis of subsequent distant organ injury. Postshock mesenteric lymph (PSML) has been shown to contain proinflammatory mediators elaborated from the ischemic gut. We hypothesize that the relative bioactivity of PSML depends on the depth and duration of circulatory shock. To first determine the timing of PSML bioactivity, we subjected rats to hemorrhagic shock (30 mm Hg x 45 min) and then resuscitation with 50 vol% of shed blood and normal saline (4x shed blood) over 2 h. Mesenteric lymph was collected hourly up to 6 h after shock. Superoxide release was measured from human neutrophils (polymorphonuclear neutrophils [PMNs]) incubated with lymph fractions collected from each of the hourly time points. Rats were then subjected to four different shock variations: (1) 30 mm Hg x 45 min, (2) 30 mm Hg x 15 min, (3) 45 mm Hg x 45 min, and (4) 45 mm Hg x 15 min, and were resuscitated. PSML flow depends on depth of shock, but not duration of shock or resuscitation volume. Maximal PSML bioactivity, as measured by PMN priming for the respiratory burst, occurred during the third postshock hour, which correlated with peak lymph flow rate. PSML bioactivity was greatest with 30 mm Hg x 45 min, followed by 30 mm Hg x 15 min, 45 mm Hg x 45 min, and 45 mm Hg x 15 min. Hemorrhagic shock provokes the release of bioactive agents in PSML that is dependent on both depth and duration of shock.

Vaisseaux lymphatiques et cancer

Survival and development of tumors depends on nutritional and respiratory biological events and exchanges ensured by blood and lymph. Tumor proliferation is associated with an increase in the vascular networks either near the tumor or intra-tumorally. Tumor tissues are able to increase their provisionment according to their needs while directing and optimizing the development of peri-tumoral vessels. The production of growth factors stimulating neo-formation of lymphatic vessels by cancer cells constitutes one of the adaptations responsible for metastatic propagation. During tumor development the lymphatic system is considered in many cases of cancer as the primary means of metastasis dissemination. The study of the lymphatic system setting and ways to block it are important points to consider in oncology.