Abnormal proportions of phenotypically and functionally distinct CD4+CD28null T-cells, the daughter progeny of repetitive antigen-driven lymphocyte proliferations, and a frequent and specific finding of chronic immunologic diseases [47], [48], are also present in the circulation (and lungs) of IPF patients singularly destined for poor outcomes [16]. This evidence concerns the gene CD4 and idiopathic pulmonary fibrosis.