Publications by authors named "Thomas G Christensen"

9 Publications

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The sst1 resistance locus regulates evasion of type I interferon signaling by Chlamydia pneumoniae as a disease tolerance mechanism.

PLoS Pathog 2013 29;9(8):e1003569. Epub 2013 Aug 29.

Section of Infectious Diseases, Boston University School of Medicine and Boston Medical Center, Boston, Massachusetts, United States of America.

The sst1, "supersusceptibility to tuberculosis," locus has previously been shown to be a genetic determinant of host resistance to infection with the intracellular pathogen, Mycobacterium tuberculosis. Chlamydia pneumoniae is an obligate intracellular bacterium associated with community acquired pneumonia, and chronic infection with C. pneumoniae has been linked to asthma and atherosclerosis. C. pneumoniae is a highly adapted pathogen that can productively infect macrophages and inhibit host cell apoptosis. Here we examined the role of sst1 in regulating the host response to infection with C. pneumoniae. Although mice carrying the sst1 susceptible (sst1(S) ) locus were not impaired in their ability to clear the acute infection, they were dramatically less tolerant of the induced immune response, displaying higher clinical scores, more severe lung inflammation, exaggerated macrophage and neutrophil influx, and the development of fibrosis compared to wild type mice. This correlated with increased activated caspase-3 in the lungs of infected sst1(S) mice. Infection of sst1(S) macrophages with C. pneumoniae resulted in a shift in the secreted cytokine profile towards enhanced production of interferon-β and interleukin-10, and induced apoptotic cell death, which was dependent on secretion of interferon-β. Intriguingly macrophages from the sst1(S) mice failed to support normal chlamydial growth, resulting in arrested development and failure of the organism to complete its infectious cycle. We conclude that the sst1 locus regulates a shared macrophage-mediated innate defense mechanism against diverse intracellular bacterial pathogens. Its susceptibility allele leads to upregulation of type I interferon pathway, which, in the context of C. pneumoniae, results in decreased tolerance, but not resistance, to the infection. Further dissection of the relationship between type I interferons and host tolerance during infection with intracellular pathogens may provide identification of biomarkers and novel therapeutic targets.
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http://dx.doi.org/10.1371/journal.ppat.1003569DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3757055PMC
March 2014

Helicobacter heilmannii gastritis in a young patient with a pet.

Gastrointest Endosc 2012 Aug;76(2):421-2

Department of Pathology and Laboratory Medicine, Boston, Massachusetts, USA.

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http://dx.doi.org/10.1016/j.gie.2012.03.1403DOI Listing
August 2012

Endoscopic versus conventional radial artery harvest for coronary artery bypass grafting: functional and histologic assessment of the conduit.

J Thorac Cardiovasc Surg 2006 Feb 4;131(2):388-94. Epub 2006 Jan 4.

Department of Cardiothoracic Surgery, Boston Medical Center, Boston, Mass 02118, USA.

Background: The radial artery's propensity for vasospasm and vulnerability to surgical trauma are well known. A less invasive endoscopic method to harvest the radial artery was recently introduced, but its effect on radial artery integrity is unknown.

Methods: To compare the effects of harvest method on radial artery function, we prospectively randomized 54 patients undergoing coronary artery bypass grafting with the radial artery into 3 groups on the basis of harvest techniques: endoscopic, conventional with cautery, and conventional with harmonic scalpel. We assessed endothelium-dependent and endothelium-independent relaxation of radial artery segments to sequential doses of acetylcholine and nitroglycerin, respectively, using standard organ-chamber methodology. Vasospasm was assessed as the vasoconstrictor response to the thromboxane analog U46619. We assessed endothelial integrity using light and electron microscopy and by rating intercellular adhesion molecule 1, vascular cell adhesion molecule 1, and P-selectin expression by means of immunohistochemistry on a semiquantitative 0- to 3-point scale. Harvest procedures were performed by a single surgeon, and data analyses were blinded to the harvesting method.

Results: Maximal relaxation-contraction responses to acetylcholine, nitroglycerin, and U46619 and effective drug concentration yielding 50% response were similar in the 3 groups. Adhesion molecule expression and histologic changes, as assessed by means of light and electron microscopy, were similar in the 3 groups.

Conclusions: Endoscopic harvest does not alter radial artery vasoreactivity or endothelial integrity compared with conventional harvest techniques. Because the endoscopic technique is less invasive, it might prove to be the technique of choice to harvest the radial artery.
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http://dx.doi.org/10.1016/j.jtcvs.2005.07.036DOI Listing
February 2006

Effect of IL-2-Bax, a novel interleukin-2-receptor-targeted chimeric protein, on bleomycin lung injury.

Int J Exp Pathol 2005 Oct;86(5):279-88

Lung Cellular and Molecular Biology Laboratory, Institute of Pulmonology, Hadassah University Hospital and Hebrew University, Hadassah Medical School, Jerusalem, Israel.

The role of lymphocytes in the pathogenesis of lung fibrosis is not clear, but the weight of the evidence supports a pro-fibrotic effect for lymphocytes. The high-affinity interleukin-2 receptor (haIL-2R) is expressed on activated, but not quiescent, T lymphocytes. This selective expression of haIL-2R provides the basis for therapeutic strategies that target IL-2R-expressing cells. We hypothesized that elimination of activated lymphocytes by IL-2R-targeted chimeric proteins might ameliorate lung fibrosis. We investigated the effects of IL-2-Bax, a novel apoptosis-inducing IL-2R-targeted chimeric protein, on bleomycin-induced lung injury in mice. Treatment groups included (i) a single intratracheal instillation of bleomycin and twice-daily intraperitoneal injections of IL-2-Bax; (ii) intratracheal bleomycin and intraperitoneal IL-2-PE66(4Glu), an older-generation chimeric protein; (iii) intratracheal bleomycin/intraperitoneal PBS; (iv) intratracheal saline/intraperitoneal PBS. Lung injury was evaluated 14 days after intratracheal instillation by cell count in bronchoalveolar lavage (BAL) fluid, semi-quantitative and quantitative histomorphological measurements and by biochemical analysis of lung hydroxyproline. Bleomycin induced a BAL lymphocytosis that was significantly attenuated by IL-2-Bax and IL-2-PE66(4Glu). However, morphometric parameters and lung hydroxyproline were unaffected by the chimeric proteins. These results show that IL-2-Bax reduces the lymphocytic infiltration of the lungs in response to bleomycin, but this effect is not accompanied by a decrease in lung fibrosis.
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http://dx.doi.org/10.1111/j.0959-9673.2005.00436.xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2517439PMC
October 2005

Adult-onset neuronal ceroid lipofuscinosis type B in an African-American.

Mov Disord 2005 Jun;20(6):752-4

Department of Neurology, School of Medicine, Boston University Medical Center, 715 Albany Street, Boston, MA 02118, USA.

We describe a rare case of adult-onset neuronal ceroid lipofuscinosis (NCL) type B with probable autosomal dominant inheritance, exhibiting behavioral and cognitive abnormalities and extrapyramidal findings. Ultrastructural examination revealed abundant fingerprint profiles in several cell types. To our knowledge, this is the first reported case of an African-American with adult-onset NCL.
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http://dx.doi.org/10.1002/mds.20406DOI Listing
June 2005

Role of interferon-gamma in the evolution of murine bleomycin lung fibrosis.

Am J Physiol Lung Cell Mol Physiol 2003 Dec 11;285(6):L1255-62. Epub 2003 Jul 11.

Lung Cellular & Molecular Biology Laboratories, Institute of Pulmonology, Hadassah University Hospital, Jerusalem 91120, Israel.

IFN-gamma production is upregulated in lung cells (LC) of bleomycin-treated C57BL/6 mice. The present study characterizes the time course, cellular source, and regulation of IFN-gamma expression in bleomycin-induced lung injury. IFN-gamma mRNA in LC from bleomycin-treated mice peaked 3 days after intratracheal instillation. IFN-gamma protein levels were increased at 6 days, as was the percentage of LC expressing IFN-gamma. CD4+, CD8+, and natural killer cells each contributed significantly to IFN-gamma production. IL-12 mRNA levels were increased at 1 day in LC of bleomycin-treated mice. Anti-IL-12 and anti-IL-18 antibodies decreased IFN-gamma production by these cells. To define the role of endogenous IFN-gamma in the evolution of bleomycin lung injury, we compared the effect of bleomycin in mice with a targeted knockout mutation of the IFN-gamma gene (IFN-gamma knockout) and wild-type mice. At 14 days after intratracheal bleomycin, total bronchoalveolar lavage cell counts and lung hydroxyproline were decreased in IFN-gamma knockouts compared with wild-type animals. There was no difference in morphometric parameters of fibrosis. Our data show that enhanced IFN-gamma production in the lungs of bleomycin-treated mice is at least partly IL-12 and IL-18 dependent. Absence of IFN-gamma in IFN-gamma knockout mice does not increase pulmonary fibrosis. Endogenous IFN-gamma may play a proinflammatory or profibrotic role in bleomycin-induced lung fibrosis.
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http://dx.doi.org/10.1152/ajplung.00303.2002DOI Listing
December 2003

Bleomycin-induced lung fibrosis in IL-4-overexpressing and knockout mice.

Am J Physiol Lung Cell Mol Physiol 2002 Nov;283(5):L1110-6

Lung Cellular and Molecular Biology Laboratory, Institute of Pulmonology, Hadassah University Hospital and The Hebrew University-Hadassah Medical School, 91120 Jerusalem, Israel.

The role of IL-4 in the development of lung fibrosis is as yet unclear. Bleomycin (Bleo) or saline (Sal) was injected intratracheally into three groups of C57BL/6J mice: transgenic animals that overexpressed IL-4 (IL-4 TG, n = 14), mice with a targeted knockout mutation of the IL-4 gene (IL-4 KO, n = 11), and wild-type (WT, n = 13) mice. At 14 days, lung fibrosis was evaluated by hydroxyproline measurement and by quantitative image analysis of fibrosis fraction and alveolar wall area fraction. Bronchoalveolar lavage cell counts in all Bleo-treated groups demonstrated an increased percentage of lymphocytes with a corresponding decrease in the percentage of macrophages. Comparing Bleo- to Sal-treated controls within each group of mice showed increases in all lung fibrosis parameters in IL-4 KO and WT, but not in any of the parameters in IL-4 TG mice. The severity of Bleo-induced fibrotic response was decreased in overexpressed IL-4 TG compared with IL-4 KO mice. These data negate a critical profibrotic role for IL-4 in Bleo-induced lung fibrosis.
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http://dx.doi.org/10.1152/ajplung.00107.2002DOI Listing
November 2002

Cyclosporin A upmodulates bleomycin-induced pulmonary fibrosis in BALB/c mice.

Respiration 2002 ;69(4):344-9

Lung Cellular and Molecular Biology Laboratory, Institute of Pulmonology, Hebrew University-Hadassah Medical School, Jerusalem, Israel.

Background: Intratracheal instillation of bleomycin (Bleo) into rodents serves as a model for human lung fibrosis. Various mouse strains respond differently to Bleo, and BALB/c mice are relatively resistant.

Objective: Since T lymphocytes have been shown to play a major role in this model, the effect of the immunomodulator cyclosporin A (CyA) on lung fibrosis was studied in Bleo-'resistant' BALB/c mice.

Methods: Pulmonary fibrosis was induced by a single intratracheal (IT) instillation of Bleo. One of the four following treatments was given to one of four groups of female BALB/c mice: (1) Bleo-CyA: IT Bleo and daily intraperitoneal (IP) injections of CyA 100 mg/day starting 1 day before IT instillation of Bleo; (2) Bleo-Sal: IT Bleo and IP injections of saline; (3) Sal-CyA: IT saline and IP CyA 100 mg/kg; (4) Sal-Sal: IT and IP saline. The animals were killed on day 14. Fibrosis was evaluated by analysis of hydroxyproline and by quantitative image analysis of the fibrosis fraction. Ex vivo IFN-gamma, IL-4, IL-13 and IL-5 secretion by peribronchial lymphatic tissue lymphocytes was measured.

Results: Pretreatment with CyA upmodulated Bleo-induced lung fibrosis in the Bleo-'resistant' BALB/c mice; hydroxyproline was higher in Bleo-CyA compared to Bleo-Sal animals and both hydroxyproline and fibrosis fraction measurements were higher in Bleo-CyA compared to Sal-Sal. Cytokine secretion by lymphocytes demonstrated increased IFN-gamma/IL-4 and IFN-gamma/IL-13 mean secretion ratios in the Bleo-CyA animals compared to the Bleo-Sal animals.

Conclusions: These results indicate that CyA upmodulates Bleo-induced lung fibrosis in Bleo-'resistant' BALB/c mice by allowing the emergence of a Th1 inflammatory response.
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http://dx.doi.org/10.1159/000063273DOI Listing
October 2002
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