CD28 and idiopathic pulmonary fibrosis: Inverse MR analysis indicated that IPF was only causally associated with certain immune cell phenotypes, including CD45RA+ CD28- CD8+ T cell absolute counts (OR=0.001, 95% CI [0.00-0.71], P=0.037), CD19 on IgD+ CD38- naive B cells (OR=0.95, 95% CI [ 0.909-0.998], P=0.042), and CD39 on CD39+ CD8+ T cells (OR=1.05, 95% CI [1.01-1.09], P=0.012; Figure 2B, Supplementary Table S2).