CD4 and idiopathic pulmonary fibrosis: Conversely, central memory CD4+ T cells (OR=0.96, 95% CI [0.930-0.999], P=0.044), terminally differentiated CD4+ T cell absolute counts (OR=0.80, 95% CI [0.65-0.98], P=0.031), and HVEM on terminally differentiated CD4+ T cells (OR=0.92, 95% CI [0.852-0.998], P=0.046) were associated with a reduced risk of developing IPF.