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2005 Progress Report: Dendritic Cell Activation by Particulate Matter and Allergen
EPA Grant Number: R832139C004Subproject: this is subproject number 004 , established and managed by the Center Director under grant R832139
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: Johns Hopkins Center for Childhood Asthma in the Urban Environment
Center Director: Breysse, Patrick
Title: Dendritic Cell Activation by Particulate Matter and Allergen
Investigators: Georas, Steven
Institution: Johns Hopkins University
EPA Project Officer: Fields, Nigel
Project Period: November 1, 2003 through October 31, 2008 (Extended to October 31, 2010)
Project Period Covered by this Report: November 1, 2004 through October 31, 2005
RFA: Centers for Children's Environmental Health and Disease Prevention Research (2003)
Research Category: Children's Health , Health Effects
Description:
Objective:The overall goal of this research project is to examine the influence of airborne particulates and bioaerosols on airway immune responses associated with asthma. The specific objectives are to: (1) investigate the mechanisms by which ambient particulate matter (APM) modulates the surface phenotype of myeloid dendritic cells (DC) differentiated in vitro to an activated state by lipopolysaccharide (LPS); and (2) investigate the mechanism by which APM modulates important immunologic functions of DC critical to host and protective immunity.
Progress Summary:The model of DC maturation used by Dr. Williams and Dr. Georas allows CD34+ myeloid precursor cells to be differentiated for 13-15 days in the presence of a cocktail of cytokines including granulocyte macrophage colony stimulating factor, stem cell factor, Flt-3 ligand, IL-4, and TNF that collectively direct the development of immature DC (iDC) cells from myeloid precursors. iDC are instructed to differentiate to mature DC (mDC) by exposing them to LPS (endotoxin) for 48 hours. LPS as the maturation signal led to the expected increases in TNF, IL-12, and IL-10 secretion and augmented surface expression of CD40, CD80, CD86, major histocompatibility complex (MHC) II, and CD83.
By contrast, APM was found to regulate several aspects of DC activation. Endocytosis (the ability to take up exogenous antigen) was downregulated as was the expression of the pattern recognition receptors toll-like receptor (TLR) 2 and TLR4 and the production of IL-10. In addition, the production of the Th2-polarizing cytokine IL-6, was markedly upregulated following stimulation of iDC with APM as was the production of TNF and IL-12. APM was washed extensively with PBS buffered with 10mM HEPES pH 7.4, and the supernatant was found to behave similarly to bulk APM. The magnitude of responses seen in the aqueous activity, however, was not as pronounced as those observed with total APM activity. Preliminary findings suggest that APM is directing a unique pattern of functional activation in human DC that in many ways mimics the effects observed with LPS stimulation alone. One of the most important observations made from these experiments is that APM-primed DC promote an increase in the IL13:IFNγ ratio in a co-culture system comprising CD4+ T Cells and APM-exposed and then washed DC. Collectively, the data is concordant with the notion that a Th2-type immune response is being promoted by APM-exposed myeloid DC. Future experiments will identify the time-course kinetics of distinct Th1- and Th2-polarizing cytokines to confirm these initial conclusions.
Findings, Relevance to Field
Our findings have several implications to the field of asthma. First, to our knowledge they are the first studies to demonstrate that ambient particulates can directly alter cells that are pivotal in the maturation and establishment of the immunologic state characteristic of asthma. DCs are the most potent antigen presenting cell in the lung. In peripheral tissues, iDC respond to innate immune signals, such as LPS, characterized by increased formation of MHC peptide complexes, a higher expression of costimulatory molecules, altered expression of chemokine receptors that facilitate movement into lymphoid tissues, and synthesis of chemokines and cytokines that influence T cell differentiation, including IL-6, IL-10, and IL-12. Not only will this influence evolution to the characteristic “Th2 bias” in asthma, but there is suggestive evidence in animal models that they are critical to altering airway responsiveness to lead to the characteristic asthma phenotype. The availability of an in vitro model to examine these processes is extremely valuable both for understanding basic pathways and for examining the basis of individual responses.
Future Activities:We will examine the effects of indoor particulates collected from smoking and nonsmoking homes for their ability to activate DC from anonymous white cell donors. As time allows, responses will be compared in cells collected from atopic donors to examine the effect of costimulation with allergens.
Journal Articles:No journal articles submitted with this report: View all 3 publications for this subproject
Supplemental Keywords:airborne particulates, asthma, dendritic cells, DC, allergens, particulate matter, PM, children’s health,
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HUMAN HEALTH, Air, Scientific Discipline, Health, RFA, PHYSICAL ASPECTS, Health Effects, Health Risk Assessment, Physical Processes, particulate matter, Allergens/Asthma, Genetics, allergens, children's health, air toxics, respiratory, air pollution, airborne pollutants, children, bioaerosols, exposure, asthma triggers, asthma, human exposure, PM
Progress and Final Reports:
2004 Progress Report
Original Abstract
2006 Progress Report
2007 Progress Report
Main Center Abstract and Reports:
R832139 Johns Hopkins Center for Childhood Asthma in the Urban Environment
Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R832139C001 The Epidemiology of Susceptibility to Airborne Particulates and Allergens to Asthma in African Americans
R832139C002 A Randomized Controlled Trial of Behavior Changes in Home Exposure Control
R832139C003 Mechanisms of Particulate-Induced Allergic Asthma
R832139C004 Dendritic Cell Activation by Particulate Matter and Allergen