Objectives Therapy with broad-spectrum antibiotics is a common practice for premature infants. This treatment can reduce the biodiversity of the fecal microbiota and may be a factor in the cause of necrotizing enterocolitis (NEC). In contrast, probiotic treatment of premature infants reduces the incidence of NEC. We hypothesized that one mechanism for these observations is the influence of bacteria on postnatal development of the mucosal immune system. Methods Expression of immune molecules and microbial sensors was investigated in the postnatal mouse gastrointestinal tract by real-time PCR. Subsequently, two-week-old specific pathogen free (SPF) and microbial reduced (antibiotic treated, MR) mice were compared for immune molecule and microbial sensor expression, mesenteric lymph node (MLN) T-cell numbers and activation, intestinal barrier function/permeability, systemic lymphocyte numbers, and T-cell phenotype commitment. Results Toll-like receptor (TLR) 2, 4, and 5 expression was highest in 2-week-old SPF mice, and this expression was decreased in MR mice. There was no difference in intestinal tight-junctional function, as evaluated by FITC-dextran uptake, but MR mice had increased bacteria translocation across the intestinal epithelial barrier. MR mice had significantly fewer splenic B-cells and MLN CD4+ T-cells, but there were normal numbers of splenic T-cells. These systemic T-cells from MR mice produced more IL-4, and less interferon-γ and IL-17, indicative of a maintenance of the fetal, T-helper cell type 2 phenotype. Conclusions This study shows that intestinal commensal microbiota have an influence on early postnatal immune development. Determining specific bacteria and/or bacterial ligands critical for this development could provide insight into the mechanisms by which broad-spectrum antibiotics and/or probiotic therapy influences the development of the mucosal immune system and mucosal-related diseases.

CXC chemokines with a glutamate-leucine-arginine (ELR) tripeptide motif (ELR؉ CXC chemokines) play an important role in leukocyte trafficking into the tissues. For reasons that are not well elucidated, circulating leukocytes are recruited into the tissues mainly in small vessels such as capillaries and venules. Because ELR ؉ CXC chemokines are important mediators of endothelial-leukocyte interaction, we compared chemokine expression by microvascular and aortic endothelium to investigate whether differences in chemokine expression by various endothelial types could, at least partially, explain the microvascular localization of endothelial-leukocyte interaction. Both in vitro and in vivo models indicate that ELR ؉ CXC chemokine expression is higher in microvascular endothelium than in aortic endothelial cells. These differences can be explained on the basis of the preferential activation of endothelial chemokine production by low intensity shear stress. Low shear activated endothelial ELR ؉ CXC chemokine production via cell surface heparan sulfates, ␤ 3 -integrins, focal adhesion kinase, the mitogen-activated protein kinase p38␤, mitogen-and stress-associated protein kinase-1, and the transcription factor.

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SummaryHuman Helicobacter pylori infection leads to multiple pathological consequences, including gastritis and adenocarcinoma. Although this association has led to the classification of H. pylori as a type 1 carcinogen, it is not clear if additional nonhelicobacter gastric microbiota play a role in these diseases. In this study, we utilized either specific pathogen-free C57BL/6 mice (B6.SPF) or mice colonized with altered Schaedler flora (B6.ASF) to evaluate the role of nonhelicobacter gastric microbiota in disease development after Helicobacter felis infection. Despite similar histological changes, H. felis persisted in B6.ASF stomachs, while H. felis could no longer be detected in the majority of B6.SPF mice. The B6.SPF mice also acquired multiple Lactobacillus spp. in their stomachs after H. felis infection. Our data indicate that potential mechanisms responsible for the ineffective H. felis clearance in the B6.ASF model include the absence of new gastric microbiota to compete for the gastric niche, the lack of expression of new gastric mucins, and a reduced ratio of H. felis-specific IgG2c:IgG1 serum antibodies. These data suggest that although H. felis is sufficient to initiate gastric inflammation and atrophy, bacterial eradication and the systemic immune response to infection are significantly influenced by pre-existing and acquired gastric microbiota. (J Histochem Cytochem 59:826-841, 2011)

BackgroundMechanisms that affect recovery from fetal and neonatal hypoxic-ischemic (H-I) brain injury have not been fully elucidated. The incidence of intrapartum asphyxia is approximately 2.5%, but the occurrence of adverse clinical outcome is much lower. One of the factors which may account for this relatively good outcome is the process of neurogenesis, which has been described in adult animals. We used a neonatal mouse model to assess new cells in the hippocampus after H-I injury.ResultsNeonatal mice underwent permanent unilateral carotid ligation on the seventh postnatal day followed by exposure to 8% hypoxia for 75 minutes. The presence of new cells was determined by bromodeoxyuridine (BrdU) incorporation into cells with sacrifice of the animals at intervals. Brain sections were stained for BrdU in combination with neuronal, glial, endothelial and microglial stains.We found a significant increase in BrdU-positive cells in the neonatal mouse hippocampus in the injured area compared to the non-injured area, most prominent in the dentate gyrus (DG) (154.5 ± 59.6 v. 92.9 ± 32.7 at 3 days after injury; 68.9 ± 23.4 v. 52.4 ± 17.1 at 35 days after injury, p < 0.0011). Among the cells which showed differentiation, those which were stained as either microglial or endothelial cells showed a peak increase at three days after the injury in the DG, injured versus non-injured side (30.5 ± 17.8 v. 2.7 ± 2.6, p < 0.0002). As in the adult animal, neurogenesis was significantly increased in the DG with injury (15.0 ± 4.6 v. 5.2 ± 1.6 at 35 days after injury, p < 0.0002), and this increase was subsequent to the appearance of the other dividing cells. Numbers of new oligodendrocytes were significantly higher in the DG on the non-injured side (7.0 ± 24.2 v. 0.1 ± 0.3, p < 0.0002), suggesting that oligodendrocyte synthesis was reduced in the injured hippocampus.ConclusionThese findings demonstrate that the neonatal animal responds to brain injury with neurogenesis, much like the adult animal. In addition, H-I insult leads to more neurogenesis than hypoxia alone. This process may play a role in the recovery of the neonatal animal from H-I insult, and if so, enhancement of the process may improve recovery.

Morbidity and mortality in infants admitted to an academic NICU did not change significantly over the academic year. These observations suggest that the quality of care of critically ill neonates is not decreased early in the academic year.

Shwachman-Diamond syndrome is a rare autosomal recessive disorder characterized by bone marrow dysfunction, exocrine pancreatic insufficiency, failure to thrive, and skeletal abnormalities. It is most commonly diagnosed in early childhood after the development of hematologic abnormalities. We report a premature infant born at 33 weeks gestation who was small for gestational age and displayed persistent cytopenias requiring transfusion. Genetic testing confirmed a diagnosis of Shwachman-Diamond syndrome (SDS).

BackgroundThe intestinal innate mucosal immune function is important in health and disease. Specifically, Toll-like receptors (TLRs) are cell surface molecules that recognize distinct molecular patterns with a resultant inflammatory response. It is generally accepted that the acquisition of the intestinal microbiota occurs within the first few days of life. The role of this colonization on the expression of TLR in the developing intestine is not well understood. We hypothesized that the acquisition of commensal bacteria would result in increased expression of gastrointestinal TLR and the associated inflammatory response.MethodsConventionally housed C57BL/6 mice were sacrificed at different time points (E 20.5, 1 day, 3 days, 1 week, 2 weeks, 3 weeks, and 6 weeks). The gastrointestinal tract was divided into stomach, small intestine, and cecum/colon. RNA was isolated using the Trizol® method (Invitrogen, Inc) and cDNA was synthesized using the First Stand Transcriptor Kit® (Roche, Inc). Real-time PCR was performed to measure the expression of TLR2, TLR4, TLR5, TLR9, and MIP-2 (murine IL-8) using Assay on Demand® (Applied Biosystems). The crossing threshold of each TLR was normalized to 18S ribosomal expression. Fold change in expression was compared to the 6-week-old animal levels. Statistical significance was set at > 4-fold change or < 0.25-fold change.ResultsTLR levels at E 20.5, 1 day, 3 days, and 1 week were not different than 6-week-old expression. In contrast, expression of gastric and colonic TLR2, -4, -5, and -9 were significantly greater in the 2-week-old mice. Intestinal TLR4 and -5 were also greater at 2 weeks. This increased expression was dampened by 3 weeks of age. Mirroring the TLR expression, MIP-2 was also significantly greater at 2 weeks.ConclusionsTLR expression is greatest in the time period associated with the acquisition of commensal mirobiota. Additionally, there is a local inflammatory response as measured by MIP-2 levels. This peak in expression is not maintained and diminishes by 6 weeks of age. Implications: The transient increase in TLR expression, coinciding with bacterial colonization, likely recruits effector cells into the mucosal immune system. This process may also play a role in the pathogenesis of necrotizing enterocolitis (NEC), a disease of premature infants. Since the median age of onset of NEC is approximately 3 weeks, the inflammatory response to the colonization of intestinal commensal microbiota could be an initiating factor in the disease.