CXCL8 and idiopathic pulmonary fibrosis: Consistent with the mRNA data, there was coregulation of IL-8 protein expression in IPF MPCs and IPF MPC progeny with fourfold higher levels of IL-8 in IPF MPCs compared with control MPCs and approximately ninefold higher levels of IL-8 protein in IPF MPC progeny compared with control MPC progeny (Fig. 1, C and D).