In parallel sections, the small SE sites, like the larger fibroblastic foci, consistently contained abundant cells expressing the myofibroblast phenotype, as indicated by α-smooth muscle actin immunoreactivity (Figure3f), but by virtue of their Wnt7B reactivity, clearly represented a subpopulation of these cells compared with the overall total myofibroblast population in IPF lungs. This evidence concerns the gene WNT7B and idiopathic pulmonary fibrosis.