Chemokine (C-C motif) receptor 2 (CCR2) ligand promotes proliferation of human and murine blood fibrocytes. Human blood fibrocytes (A) were stimulated with human chemokine (C-C motif) ligand 2 (hCCL2) or platelet-derived growth factor (PDGF)-AB and murine blood fibrocytes (pooled blood from n = 10 mice) (B) were stimulated with mCCL2, mCCL12 or PDGF-AB. Cells were grown for 4 days before proliferative activity was measured using CellTiter-Glo Luminescent Cell viability. *P < 0.05, significantly different compared with untreated fibrocytes. ***P < 0.005, significantly different compared with untreated fibrocytes. Data are expressed as the mean ± SEM (n = 3 replicates per treatment group) (representative of three separate experiments).