CXCL13 and idiopathic interstitial pneumonia: Elevated serum levels of several proteins have been associated with worse prognosis in IPF, including surfactant protein A (SP-A) and D (SP-D)71,72, mucin 1 (KL-6/MUC1)73, CC-chemokine ligand 18 (CCL18)74, C-X-C motif chemokine 13 (CXCL13)75,76, periostin77, fibulin-178, matrix metalloproteinases MMP-1 and MMP-779,80, interleukin-8 (IL-8), intercellular adhesion molecule (ICAM)-180, and lysyl oxidase-like 2 protein (LOXL2)81.