Identification of HLA-DR-bound peptides presented by human bronchoalveolar lavage cells in sarcoidosis

Sarcoidosis is an inflammatory disease of unknown etiology, most commonly affecting the lungs. Activated CD4(+) T cells accumulate in the lungs of individuals with sarcoidosis and are considered to be of central importance for inflammation. We have previously shown that Scandinavian sarcoidosis patients expressing the HLADR allele DRB1*0301 are characterized by large accumulations in the lungs of CD4(+) T cells expressing the TCR AV2S3 gene segment. This association afforded us a unique opportunity to identify a sarcoidosis-specific antigen recognized by AV2S3(+) T cells. To identify candidates for the postulated sarcoidosis-specific antigen, lung cells from 16 HLA-DRB1*0301(pos) patients were obtained by bronchoalveolar lavage. HLA-DR molecules were affinity purified and bound peptides acid eluted. Subsequently, peptides were separated by reversed-phase HPLC and analyzed by liquid chromatography-mass spectrometry. We identified 78 amino acid sequences from self proteins presented in the lungs of sarcoidosis patients, some of which were well-known autoantigens such as vimentin and ATP synthase. For the first time, to our knowledge, we have identified HLA-bound peptides presented in vivo during an inflammatory condition. This approach can be extended to characterize HLA-bound peptides in various autoimmune settings.