This proposal will test the hypothesis that immunity has a prominent role in the pathogenesis of sarcoidosis, as suggested by abnormalities of the immune function and by the presence of antibodies, including rheumatoid factors and antinuclear antibodies found in this disorder. In addition, sarcoidosis coexists with other systemic inflammatory diseases, and patients frequently show cutaneous anergy and hypergammaglobulinemia. We propose to develop a panel of antibodies/autoantibodies with high sensitivity and specificity to identify patients with sarcoidosis and help to distinguish these patients from controls and individuals with other pulmonary diseases. For this purpose we will construct a T7 phage cDNA library of potential sarcoidosis antigens using mRNA isolated from affected lymph node tissue of patients with sarcoidosis. This cDNA library will be immunoscreened with sera from patients with sarcoidosis containing high titer IgG antibodies and the cloned colonies will be used to construct an antigen microarray that will be hybridized with sera from cases with lung sarcoidosis and controls. Control sera will be obtained from patients with sero-positive rheumatoid arthritis and from patients with a history of tuberculosis. Sequence analyses of informative phage inserts recognized as antigens by sarcoidosis patient sera may identify antigens associated with the etiopathogenesis of sarcoidosis. The autoantibody classifier will be validated with independently obtained collections of sera from cases and controls. In the future, this approach may identify molecular targets useful for the treatment of sarcoidosis.