Department of Immunology, University of Washington, Seattle, Washington 98195, USA.|Department of Immunology, University of Washington, Seattle, Washington 98195, USA.|Department of Immunology, University of Washington, Seattle, Washington 98195, USA.|Department of Immunology, University of Washington, Seattle, Washington 98195, USA.|Department of Immunology, University of Washington, Seattle, Washington 98195, USA.|Department of Immunology, University of Washington, Seattle, Washington 98195, USA.