Ar. Dongre et al., In vivo MHC class II presentation of cytosolic proteins revealed by rapid automated tandem mass spectrometry and functional analyses, EUR J IMMUN, 31(5), 2001, pp. 1485-1494
We report a strategy for high through-put sequence analyses of large MHC cl
ass Ii-bound peptide repertoires which combines automated electrospray ioni
zation tandem mass-spectrometry with computer-assisted interpretation of th
e tandem mass spectra using the algorithm SEQUEST. This powerful approach d
iscerned 128 peptide sequences displayed by the murine MHC class II molecul
e I-A(b) in activated B cells and macrophages, including a surprisingly lar
ge number of peptides derived from self cytosolic proteins. Mice lacking th
e chaperone molecule H-2M were used to generate T cells specific for select
ed self peptides. Functional T cell analyses of ex vivo antigen-presenting
cells indicated that peptides originating from cytosolic proteins are effic
iently presented by splenic and thymic dendritic cells, but less so by rest
ing B cells or thymic cortical epithelial cells. These results suggest that
central tolerance to at least some MHC class Ii-bound self peptides derive
d from cytosolic proteins exists in vivo.