Research Article Legionella pneumophila down-regulates MHC class I expression of human monocytic host cells and thereby inhibits T cell activation

Legionella (L.) pneumophila, the causative agent of Legionnaires' disease, is an intracellular pathogen of alveolar macrophages that resides in a com- partment displaying features of endoplasmatic reticulum (ER). In this study, we show that intracellular multiplica- tion of L. pneumophila results in a remarkable decrease in MHC class I expression by the infected monocytes. Dur- ing intracellular multiplication, L. pneumophila absorbs ER-resident chaperons such as calnexin and BiP, mole-