We analyze cells and soluble mediators in the lungs to understand the pathogenesis of the inflammatory disease sarcoidosis, which serves as an excellent model for other pulmonary inflammatory disorders.
The biological material is obtained through bronchoscopy with bronchoalveolar lavage (BAL), i.e. from the focus of the inflammation. Also, biopsies and peripheral blood specimens are routinely obtained. Sarcoidosis is characterized by lung accumulated activated T helper (CD4+) cells that are believed to be of central importance for the inflammatory reaction, which results in granuloma formation and in some patients in the development of fibrosis.
Anders Eklund, M.D. Ph.D. Professor
Johan Grunewald, M.D. Ph.D. Professor
Jan Wahlström, Associate Professor
We previously described a strict correlation between HLA-DRB1*0301 and lung accumulated CD4+ T cells expressing the T cell receptor AV2S3 gene segment. Detailed analyses of the AV2S3+ BAL T cells strongly indicated that they have recognized a sarcoidosis associated antigen and proliferated in response to it. In order to identify such an antigen, we recently eluted peptides bound to HLA-DR molecules from BAL fluid cells of DRB1*03+ sarcoidosis patients and sequenced them by mass spectrometry. Thus we have for the first time been able to identify antigens locally presented during an inflammatory condition. These peptides, and other candidate antigens, are used for in vitro stimulation experiments to see if any of them is the long sought-after sarcoidosis antigen. T cell reactivities have indeed been detected against the mycobacterial enzyme mKatG as well as some peptides derived from endogenous proteins, indicating that autoimmune responses may contribute to the inflammatory process.
Our finding that the HLA-type predicts the prognosis enables us to characterize the immune response in two subgroups of sarcoidosis patients (DRB1*03 versus DRB1*14 and *15), each with a very distinct prognosis, in order to understand what factors may lead to resolution versus perpetuation of the inflammatory reaction.
Using a proteomic approach, we analyze and characterize protein expression in BAL fluid of sarcoidosis patients as compared to healthy controls. Several putative biomarkers for sarcoidosis have already been identified. In addition, we apply recently developed techniques to identify membrane-associated proteins of BAL cells, since such proteins may contain disease specific antigens.