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Infection and Immunity, June 2006, p. 3232-3238, Vol. 74, No. 6
0019-9567/06/$08.00+0 doi:10.1128/IAI.02067-05
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
Department of Microbiology and Immunology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107,1 Department of Biochemistry and Molecular Biology, Mayo Clinic Scottsdale, Scottsdale, Arizona 85259,2 Department of Pathobiology, University of Pennsylvania, Philadelphia, Pennsylvania 191043
Received 22 December 2005/ Returned for modification 9 February 2006/ Accepted 24 March 2006
Several studies have demonstrated roles for eosinophils during innate and adaptive immune responses to helminth infections. However, evidence that eosinophils are capable of initiating an immune response to parasite antigens is lacking. The goal of the present in vitro study was to investigate the potential of eosinophils to serve as antigen-presenting cells (APC) and initiate an immune response to parasite antigens. Purified eosinophils were exposed to soluble Strongyloides stercoralis antigens, and the expression of various surface markers involved in cell activation was examined. Antigen-exposed eosinophils showed a sixfold increase in expression levels of CD69 and major histocompatibility complex (MHC) class II, a fourfold increase in levels of T-cell costimulatory molecule CD86, and a twofold decrease in levels of CD62L compared to eosinophils cultured in medium containing granulocyte-macrophage colony-stimulating factor. The ability of eosinophils to present antigen to T cells was determined by culturing them with T cells in vitro. Eosinophils pulsed with antigen stimulated antigen-specific primed T cells and CD4+ T cells to increase interleukin-5 (IL-5) production. The blocking of MHC class II expression on eosinophils inhibited their ability to induce IL-5 production by CD4+ T cells in culture. Antigen-pulsed eosinophils were able to prime naïve T cells and CD4+ T cells in culture and polarized them into Th2 cells producing IL-5 similar to that induced by antigen-loaded dendritic cells. These results demonstrate that eosinophils are capable of activating antigen-specific Th2 cells inducing the release of cytokines and assist in the priming of naïve T cells to initiate Th2 responses against infection. This study highlights the potential of eosinophils to actively induce immune responses against infection by amplifying antigen-specific Th2-cell responses.
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