MHC class II tetramers containing influenza hemagglutinin and EBV EBNA1 epitopes detect reliably specific CD4(+) T cells in healthy volunteers.

Tracking antigen specific T cells with major histocompatibility complex (MHC) tetramers has provided us with insights into the dynamics of the adaptive immune system and holds great promise to aid in patient management and drug and vaccine development. Progress has been made primarily using MHC class I tetramers to monitor CD8(+) T cells, whereas corresponding efforts to stain CD4(+) T cells with class II tetramers have not been as successful. Two major reasons have been proposed for this lack of progress: (1).