Interferon (IFN)-α inhibits fibrocyte differentiation. Human PBMCs were cultured in different concentrations of IFN-α. After 5 days, the cells were air-dried, fixed and stained, and the number of fibrocytes was counted. The results are means ± SEM of fibrocytes per 2.5 × 105 PBMCs (n = 3 separate experiments). *P < 0.05 and **P < 0.01 compared to no IFN-α control (one-way ANOVA, Dunnett's test).