Objective To examine the impact of C-reactive protein (CRP) on the expression of interleukin-6 (IL-6), inflammatory cytokine, in cultured human pulmonary artery smooth muscle cells (hPASMCs) in order to find out the cause of pulmonary artery hypertension (PAH). Method The hPASMCs were cultured and stimulated by different concerntrations of CRP (5 - 200 μg/ml) for different lengths of time. The activity of nuclear factor-κB (NF-κB) was evaluated by electrophoretic gel mobility shift assay (EMSA). The expression of IL-6 mRNA and the level of IL-6 protein were measured by using real-time PCR and ELISA, respectively. Results CRP increased IL-6 production in hPASMCs in a dose-dependent manner. The increase in IL-6 at concerntration of 200 μg/mL in the CRP group was as high as 2.8times that in the control group. CRP also significantly induced the activation of NF-κB in hPASMCs. The effect of CRP on the inflammatory cytokine, IL-6, was inhibited by the specific FcγⅡa receptor antibody.Conclusions In vitro, CRP increases the production of IL-6 in hPASMCs mediated by FcγⅡa receptor and NF-κB translocation. These data offer important insights into the role of CRP in the pathogenesis of PAH.