A Convenient Model of Severe, High Incidence Autoimmune Gastritis Caused by Polyclonal Effector T Cells and without Perturbation of Regulatory T Cells

Autoimmune gastritis results from the breakdown of T cell tolerance to the gastric H+/K+ ATPase. The gastric H+/K+ ATPase is responsible for the acidification of gastric juice and consists of an α subunit (H/Kα) and a β subunit (H/Kβ). Here we show that CD4+ T cells from H/Kα-deficient mice (H/Kα−/−) are highly pathogenic and autoimmune gastritis can be induced in sublethally irradiated wildtype mice by adoptive transfer of unfractionated CD4+ T cells from H/Kα−/− mice. All recipient mice consistently developed the most severe form of autoimmune gastritis 8 weeks after the transfer, featuring hypertrophy of the gastric mucosa, complete depletion of the parietal and zymogenic cells, and presence of autoantibodies to H+/K+ ATPase in the serum. Furthermore, we demonstrated that the disease significantly affected stomach weight and stomach pH of recipient mice. Depletion of parietal cells in this disease model required the presence of both H/Kα and H/Kβ since transfer of H/Kα−/− CD4+ T cells did not result in depletion of parietal cells in H/Kα−/− or H/Kβ−/− recipient mice. The consistency of disease severity, the use of polyclonal T cells and a specific T cell response to the gastric autoantigen make this an ideal disease model for the study of many aspects of organ-specific autoimmunity including prevention and treatment of the disease

Intravenous alteplase for stroke with unknown time of onset guided by advanced imaging: systematic review and meta-analysis of individual patient data

Background: Patients who have had a stroke with unknown time of onset have been previously excluded from thrombolysis. We aimed to establish whether intravenous alteplase is safe and effective in such patients when salvageable tissue has been identified with imaging biomarkers. Methods: We did a systematic review and meta-analysis of individual patient data for trials published before Sept 21, 2020. Randomised trials of intravenous alteplase versus standard of care or placebo in adults with stroke with unknown time of onset with perfusion-diffusion MRI, perfusion CT, or MRI with diffusion weighted imaging-fluid attenuated inversion recovery (DWI-FLAIR) mismatch were eligible. The primary outcome was favourable functional outcome (score of 0–1 on the modified Rankin Scale [mRS]) at 90 days indicating no disability using an unconditional mixed-effect logistic-regression model fitted to estimate the treatment effect. Secondary outcomes were mRS shift towards a better functional outcome and independent outcome (mRS 0–2) at 90 days. Safety outcomes included death, severe disability or death (mRS score 4–6), and symptomatic intracranial haemorrhage. This study is registered with PROSPERO, CRD42020166903. Findings: Of 249 identified abstracts, four trials met our eligibility criteria for inclusion: WAKE-UP, EXTEND, THAWS, and ECASS-4. The four trials provided individual patient data for 843 individuals, of whom 429 (51%) were assigned to alteplase and 414 (49%) to placebo or standard care. A favourable outcome occurred in 199 (47%) of 420 patients with alteplase and in 160 (39%) of 409 patients among controls (adjusted odds ratio [OR] 1·49 [95% CI 1·10–2·03]; p=0·011), with low heterogeneity across studies (I2=27%). Alteplase was associated with a significant shift towards better functional outcome (adjusted common OR 1·38 [95% CI 1·05–1·80]; p=0·019), and a higher odds of independent outcome (adjusted OR 1·50 [1·06–2·12]; p=0·022). In the alteplase group, 90 (21%) patients were severely disabled or died (mRS score 4–6), compared with 102 (25%) patients in the control group (adjusted OR 0·76 [0·52–1·11]; p=0·15). 27 (6%) patients died in the alteplase group and 14 (3%) patients died among controls (adjusted OR 2·06 [1·03–4·09]; p=0·040). The prevalence of symptomatic intracranial haemorrhage was higher in the alteplase group than among controls (11 [3%] vs two [<1%], adjusted OR 5·58 [1·22–25·50]; p=0·024). Interpretation: In patients who have had a stroke with unknown time of onset with a DWI-FLAIR or perfusion mismatch, intravenous alteplase resulted in better functional outcome at 90 days than placebo or standard care. A net benefit was observed for all functional outcomes despite an increased risk of symptomatic intracranial haemorrhage. Although there were more deaths with alteplase than placebo, there were fewer cases of severe disability or death. Funding: None

Molecular Pathogenesis of Infections Caused by Legionella pneumophila

Summary: The genus Legionella contains more than 50 species, of which at least 24 have been associated with human infection. The best-characterized member of the genus, Legionella pneumophila, is the major causative agent of Legionnaires' disease, a severe form of acute pneumonia. L. pneumophila is an intracellular pathogen, and as part of its pathogenesis, the bacteria avoid phagolysosome fusion and replicate within alveolar macrophages and epithelial cells in a vacuole that exhibits many characteristics of the endoplasmic reticulum (ER). The formation of the unusual L. pneumophila vacuole is a feature of its interaction with the host, yet the mechanisms by which the bacteria avoid classical endosome fusion and recruit markers of the ER are incompletely understood. Here we review the factors that contribute to the ability of L. pneumophila to infect and replicate in human cells and amoebae with an emphasis on proteins that are secreted by the bacteria into the Legionella vacuole and/or the host cell. Many of these factors undermine eukaryotic trafficking and signaling pathways by acting as functional and, in some cases, structural mimics of eukaryotic proteins. We discuss the consequences of this mimicry for the biology of the infected cell and also for immune responses to L. pneumophila infection

Cellularity of stomach-draining and non-draining lymph nodes.

<p>(A) The number of cells in the paragastric and inguinal lymph nodes from recipient mice 8 weeks after transfer of either wildtype or H/Kα^−/− CD4⁺ T cells. (B) The percentage of effector/memory T cells in the donor population with the phenotype CD44^hiCD62L^lo in CD90.2⁺ CD4⁺ T cells. Data pooled from four independent experiments. Each circle represents the data from one mouse. Mann-Whitney <i>U</i> test was used; bars, mean, **, P<0.01 and ***, P<0.001.</p

Elevated immune response to immunisation with H⁺/K⁺ ATPase in H/Kα^−/− mice.

<p>WT and H/Kα^−/− mice were immunised with H⁺/K⁺ ATPase as described in “<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0027153#s4" target="_blank">Materials and Methods</a>”. (A) H⁺/K⁺ ATPase-specific autoantibodies in serum were detected by ELISA using serial 2-fold dilutions of mouse sera, with a starting dilution factor of 5. Data is representative of three independent experiments. Error bars, standard error. (B) Cells from inguinal lymph nodes were cultured for 72 hrs with splenic DC, and T cell proliferation was assessed by incorporation of ³H-thymidine. For each mouse, T cells were cultured in triplicate with either DC with gastric membrane or with DC alone. The mean cpm of T cells cultured with DC with antigen was divided by the mean cpm of the same T cells cultured with DC alone to calculate the stimulation index. Data pooled from four independent experiments. In (B), each circle represents the data from one mouse. Mann-Whitney <i>U</i> test was used; bars, mean and ***, P<0.001.</p

Autoimmune gastritis does not develop in the absence of gastric H/Kα or H/Kβ.

<p>Gastric pathology in (A) H/Kα^−/− mice received either H/Kα^−/− CD4⁺ T cells or no inoculum (−) (B) H/Kβ^−/− mice received either H/Kα^−/− CD4⁺ T cells or no inoculum (−) (C) WT mice received H/Kα^−/− CD4⁺ T cells. Images representative of results of at least 9 mice in each group are shown. (D) Serum samples were collected from H/Kα^−/−, H/Kβ^−/− or WT mice that received CD4⁺ T cells from H/Kα^−/− mice. H⁺/K⁺ ATPase-specific autoantibodies in serum were detected by ELISA using serial 2-fold dilutions of mouse sera, with a starting dilution factor of 50. Data pooled from four independent experiments. Error bars, standard error.</p

Mice with autoimmune gastritis have an increased level of Foxp3⁺ Treg cells in the stomach.

<p>Cells were harvested from (A, B) paragastric lymph node, inguinal lymph node and (A, C) stomach tissue for intracellular staining of Foxp3. The numbers indicate the percentages of Foxp3⁺ Treg cells in donor CD90.2⁺CD4⁺ T cells in paragastric and inguinal lymph nodes and Foxp3⁺ Treg cells in total CD4⁺ T cells in stomach tissue. Data pooled from three independent experiments. In (B) and (C), each circle represents the data from one mouse. Mann-Whitney <i>U</i> test was used; bars, mean, and **, P<0.01.</p

Severity of autoimmune gastritis correlates to stomach weight.

<p>Mice were killed at indicated time points after transfer of CD4⁺ T cells from H/Kα^−/− mice and the severity of autoimmune gastritis was determined. Data were pooled from six independent experiments. Each circle represents the data from one mouse. Bars, mean.</p

Significant difference in stomach weight among gastritis scores.

<p>Thymectomy was performed on BALB.B6-<i>Gasa</i> congenic mice on day 3 of age and mice killed at 12 weeks. The severity of autoimmune gastritis and stomach weight was determined. Data pooled from at least 100 independent thymectomies. Each circle represents the data from one mouse. Mann-Whitney <i>U</i> test was used; bars, mean, **, P<0.01 and ***, P<0.001.</p