CXCR4 and idiopathic pulmonary fibrosis: In areas of ACTA2 positive fibrosis in IPF lungs (Fig. 7B,F,J) we observed no expression of CXCR4 within fibroblastic foci (Fig. 7K), however expression of CXCR4 was evident at the periphery of the foci (Fig. 7G) and in areas with either pockets of fibrosis (Fig. 7C) or in less dense wide spread fibrosis (Fig. 7G).