HLA-DRB1 and idiopathic pulmonary fibrosis: Based on these initial findings, validation cohorts were prospectively compiled, consisting of HLA data from IPF subjects at the NIH and results of DRB1*15 determinations using blood or tissue specimens from IPF patients at U. Chicago, Inova, Stanford, the IPF outpatient clinic at U. Pgh., as well as an additional volunteer U. Pgh.