CD4+T Cells and Toll-Like Receptors RecognizeSalmonellaAntigens Expressed in Bacterial Surface Organelles

Abstract

A better understanding of immunity to infection is revealed from the characteristics of microbial ligands recognized by host immune responses. Murine infection with the intracellular bacteriumSalmonellagenerates CD4⁺T cells that specifically recognizeSalmonellaproteins expressed in bacterial surface organelles such as flagella and membrane vesicles. These naturalSalmonellaantigens are also ligands for Toll-like receptors (TLRs) or avidly associated with TLR ligands such as lipopolysaccharide (LPS). PhoP/PhoQ, a regulon controllingSalmonellavirulence and remodeling of LPS to resist innate immunity, coordinately represses production of surface-exposed antigens recognized by CD4⁺T cells and TLRs. These data suggest that genetically coordinated surface modifications may provide a growth advantage forSalmonellain host tissues by limiting both innate and adaptive immune recognition.