(A) Shown is the autoantibody immunoreactivity against BPIFB1 and KCNRG as light units (LU) using the luciferase immunoprecipitation systems (LIPS) immunoassay in 62 patients with thymoma with (n = 13) or without (n = 49) lung involvement, and in 27 recombination-activating gene (RAG)-deficient patients with (n = 19) or without (n = 8) lung involvement. Dotted lines represent the cutoff values for determining autoantibody seropositivity. (B) Representative chest CT image from a patient with thymoma with lung disease. (C and D) Representative images from an endobronchial (C) and transbronchial (D) biopsy of the same patient with thymoma with lung disease. Shown are H&E and immunohistochemical staining with the lymphocyte markers CD3, CD4, CD8, and CD20. Scale bars, 100 μm. (E) Representative chest CT image from a RAG-deficient patient with lung disease.