CD28 and idiopathic pulmonary fibrosis: Conversely, CD25 on activated CD4 Tregs (OR=0.80, 95% CI [0.67-0.97], P=0.020), CD28 on resting CD4 Tregs (OR=0.80, 95% CI [0.66-0.98], P=0.033), CD39 on CD39+ CD8+ T cells (OR=0.87, 95% CI [0.77-0.98], P=0.024), CD127 on CD45RA- CD4 not Tregs (OR=0.89, 95% CI [0.79-0.99], P=0.036), CD127- CD8+ T cell %CD8+ T cell (OR= 0.888, 95% CI [0.791-0.997], P=0.044), and CD28 on activated CD4 Tregs (OR=0.89, 95% CI [0.81-0.99], P=0.035) were associated with a reduced risk of IPF development.