In animal models, by using bleomycin to induce PF in wildtype and CXCR2 knockout mice, the authors demonstrated that reductions in CXCR2 signaling lead to the increased expression of matrix metalloproteinase 9 (MMP9), which has been previously implicated in lung remodeling in PF [123]. This evidence concerns the gene MMP9 and pemphigus foliaceus.