br Acknowledgments br Introduction Sarcoidosis

Acknowledgments
Introduction Sarcoidosis is an inflammatory granulomatous disease of unknown etiology affecting multiple organs, such as the lungs, skin, CNS, and eyes (Costabel, 2001; Costabel and Hunninghake, 1999; Iannuzzi et al., 2007; Hunninghake et al., 1999). Common features shared by patients with sarcoidosis are the presence of non-caseating granuloma, a lack of cutaneous reaction to tuberculin skin testing (PPD) and increased local and circulating inflammatory cytokines (Costabel, 2001; Costabel and Hunninghake, 1999; Iannuzzi et al., 2007). In addition, there is evidence of abnormal immune function accompanied by hypergammaglobulinemia (Iannuzzi et al., 2007). Sarcoidosis shares striking clinical and pathological similarities with infectious granulomatous diseases, especially Mycobacteria tuberculosis (MTB) (Iannuzzi et al., 2007; Prince et al., 2003). Although there is mounting evidence of the presence of nonviable bacterial components (including MTB and Propionibacterium acnes) in sarcoidosis tissue (Gupta et al., 2007; Chen et al., n.d.; Negi et al., 2012), all attempts to isolate viable MTB or other microbial pathogens from sarcoidosis tissue have failed (Hunninghake et al., 1999; Chen et al., 2008). Intradermal injection of the Kveim–Siltzbach suspension (a granulomatous splenic tissue suspension) induces granuloma formation weeks later in sarcoidosis patients suggesting presence of antigen(s) in granuloma tissue and host immunoreactivity to these c-met inhibitor (Dubaniewicz, 2010; Hajizadeh et al., 2007; Hiramatsu et al., 2003; Fox et al., 1983; Munro and Mitchell, 1987; Siltzbach and Ehrlich, 1954). Several studies using state-of-the-art technologies have attempted to identify sarcoidosis antigens or to identify the underlying genetic and environmental factors (Hajizadeh et al., 2007; Chen and Moller, 2007; Zhang et al., 2013), yet unifying environmental or genetic factors as initiators of this disease have not been found (Hunninghake et al., 1999; Dubaniewicz, 2010; Eishi et al., 2002; Oswald-Richter and Drake, 2010). These studies reported a number of markers or variations in gene expression signatures, however failed to discriminate between sarcoidosis and other inflammatory or granulomatous diseases (Koth et al., 2011; Maertzdorf et al., 2012). This is partly due to the fact that several inflammatory diseases may respond to various antigens with activation of a similar transcriptome and/or inflammatory gene expression profiles (Koth et al., 2011; Maertzdorf et al., 2012). Proteomics, genomics, transcriptomics, and high throughput technology clearly suggest that early immune reaction to diverse antigens is highly prevalent in a large number of rheumatic, neoplastic, and inflammatory diseases such as sarcoidosis (Koth et al., 2011; Maertzdorf et al., 2012; Bons et al., 2007; Stone et al., 2013). Since non-caseating granulomas, cutaneous anergy and hypergammaglobulinemia suggest an immune dysfunction in this disease, we hypothesize that sarcoidosis is triggered by a group of unknown antigens represented in the host immune cells. To identify the elusive antigen(s), we developed a heterologous cDNA library derived from bronchoalveolar cell (BAL) samples and total white blood cells (WBC) from sarcoidosis patients. We then combined both sarcoid-derived libraries with cultured human monocytes and embryonic lung fibroblast cDNA libraries to build a complex sarcoidosis library (CSL). Furthermore, we used antibody recognition and random plaque selection during biopanning of the cDNA libraries to minimize the confounding effects of autoantibodies unrelated to sarcoidosis. This approach has been successfully applied in biomarker discovery for the diagnosis of lung, head and neck and breast cancer (Fernandez-Madrid et al., 2004; Fernandez-Madrid et al., 1999; Lin et al., 2007). We tested whether this novel library represents relevant antigens and can specifically be recognized by high IgG titers present in sera of sarcoidosis subjects. The essential feature that distinguishes our method from previous studies is that we used the exquisite power of antibody recognition present in human sera to interrogate the potential antigens present in macrophages and monocytes.