A novel murine infection model for Shiga toxin-producing Escherichia coli

Enterohemorrhagic E. coli (EHEC) is an important subset of Shiga toxin-producing (Stx-producing) E. coli (STEC), pathogens that have been implicated in outbreaks of food-borne illness and can cause intestinal and systemic disease, including severe renal damage. Upon attachment to intestinal epithelium, EHEC generates attaching and effacing (AE) lesions characterized by intimate attachment and actin rearrangement upon host cell binding. Stx produced in the gut transverses the intestinal epithelium, causing vascular damage that leads to systemic disease. Models of EHEC infection in conventional mice do not manifest key features of disease, such as AE lesions, intestinal damage, and systemic illness. In order to develop an infection model that better reflects the pathogenesis of this subset of STEC, we constructed an Stx-producing strain of Citrobacter rodentium, a murine AE pathogen that otherwise lacks Stx. Mice infected with Stx-producing C. rodentium developed AE lesions on the intestinal epithelium and Stx-dependent intestinal inflammatory damage. Further, the mice experienced lethal infection characterized by histopathological and functional kidney damage. The development of a murine model that encompasses AE lesion formation and Stx-mediated tissue damage will provide a new platform upon which to identify EHEC alterations of host epithelium that contribute to systemic disease

PD-L1 regulates the development, maintenance, and function of induced regulatory T cells

Both the programmed death (PD) 1–PD-ligand (PD-L) pathway and regulatory T (T reg) cells are instrumental to the maintenance of peripheral tolerance. We demonstrate that PD-L1 has a pivotal role in regulating induced T reg (iT reg) cell development and sustaining iT reg cell function. PD-L1−/− antigen-presenting cells minimally convert naive CD4 T cells to iT reg cells, showing the essential role of PD-L1 for iT reg cell induction. PD-L1–coated beads induce iT reg cells in vitro, indicating that PD-L1 itself regulates iT reg cell development. Furthermore, PD-L1 enhances and sustains Foxp3 expression and the suppressive function of iT reg cells. The obligatory role for PD-L1 in controlling iT reg cell development and function in vivo is illustrated by a marked reduction in iT reg cell conversion and rapid onset of a fatal inflammatory phenotype in PD-L1−/−PD-L2−/− Rag−/− recipients of naive CD4 T cells. PD-L1 iT reg cell development is mediated through the down-regulation of phospho-Akt, mTOR, S6, and ERK2 and concomitant with the up-regulation of PTEN, all key signaling molecules which are critical for iT reg cell development. Thus, PD-L1 can inhibit T cell responses by promoting both the induction and maintenance of iT reg cells. These studies define a novel mechanism for iT reg cell development and function, as well as a new strategy for controlling T reg cell plasticity

Robot-Assisted Thoracoscopic Resection of a Posterior Mediastinal Mullerian Cyst

First described in 2005, the Mullerian derived cyst in the mediastinum is a rare finding with few subsequent reports. We report a case of Mullerian cyst occurring in the mediastinum of a 49-year-old female that was resected by robot-assisted thoracoscopic surgery. To our knowledge, this is the first report of robot-assisted resection of Hattori’s cyst. Histopathologic analysis revealed ciliated Mullerian-type tubal epithelium positive for paired box gene 8 (PAX8), estrogen receptor (ER), and progesterone receptor (PR), confirming Mullerian differentiation. We also review the clinical presentation, pathology, and differential diagnosis of such cysts

Encapsulating Peritoneal Sclerosis Presenting after Two Donor Kidney Transplantations: A Case Report and Literature Review

Encapsulating peritoneal sclerosis is a rare, recurring complication in peritoneal dialysis (PD) patients. With a mortality rate of 51%, it continues to be a therapeutic enigma among clinicians. However, the incidence after kidney transplantation (KT) has rarely been reported. We report a unique case of encapsulating peritoneal sclerosis (EPS), occurring years after failed initial living KT, and diagnosed after second deceased donor kidney transplantation. A 35-year-old male, on prior PD for 4 years, followed by failed KT of 8 years, was presented with abdominal pain, weight loss, and vomiting, 7 months after his second deceased donor KT. An abdominal computed tomography showed intra-abdominal loculated fluid collection, but no obstruction. Exploratory laparotomy revealed extensive peritoneal thickening and blocked intestinal loops. Histopathology was indicative of EPS with fibrous adhesions and sclerotic tissues. Besides restarting his immunosuppressive medications, tamoxifen therapy was initiated as definitive medical management. Currently, he is in clinical remission, follows at transplant clinic, and still experiences episodes of small bowel obstruction. Though the incidence of EPS after KT has been observed sporadically worldwide, none has been reported in the USA. Despite its prevalence in PD patients, therapeutic interventions attempted so far, are not definitive

Viral antigen density and confinement time regulate the reactivity pattern of CD4 T-cell responses to vaccinia virus infection

T-cell recognition of ligands is polyspecific. This translates into antiviral T-cell responses having a range of potency and specificity for viral ligands. How these ligand recognition patterns are established is not fully understood. Here, we show that an activation threshold regulates whether robust CD4 T-cell activation occurs following viral infection. The activation threshold was variable because of its dependence on the density of the viral peptide (p)MHC displayed on infected cells. Furthermore, the activation threshold was not observed to be a specific equilibrium affinity (K(D)) or half-life (t(1/2)) of the TCR-viral pMHC interaction, rather it correlated with the confinement time of TCR-pMHC interactions, i.e., the half-life (t(1/2)) of the interaction accounting for the effects of TCR-pMHC rebinding. One effect of a variable activation threshold is to allow high-density viral pMHC ligands to expand CD4 T cells with a variety of potency and peptide cross-reactivity patterns for the viral pMHC ligand, some of which are only poorly activated by infections that produce a lower density of the viral pMHC ligand. These results argue that antigen concentration is a key component in determining the pattern of K(D), t(1/2) and peptide cross-reactivity of the TCRs expressed on CD4 T cells responding to infection

Acute kidney injury due to intravenous bleach injection

INTRODUCTION: Sodium hypochlorite is the active ingredient in bleach, a ubiquitous household disinfectant, and has known toxicities depending on route of exposure and amount. Acute kidney injury due to sodium hypochlorite exposure has never been reported. Patients that did develop nephrotoxicity following bleach exposure did so due to development of other risk factors for kidney injury such as volume depletion or sepsis. DISCUSSION: We report a patient who presented with black urine after parenteral self-administration of a large quantity of bleach. We review the clinical presentation, laboratory and biopsy findings, and outcome as well as discuss possible mechanisms of sodium hypochlorite toxicity and management strategies