In particular, C2a and C2c show the highly abundant protein species in IPF, composed of CAYP1, IGKC, TTHY, HBA, ILEU, IGHA1, SFTA, and FRIL, while C2b and C2d group gather the protein species more abundant in both IPF and LC-IPF compared to CTRLs, such as IGKC, APOA1, S10AB, PRDX1, HPT, GDIR1, S10A6, B2MG, CYTB, HBA, and FABP4. This evidence concerns the gene APOA1 and idiopathic pulmonary fibrosis.