Several cytokines (CX3CR1, CCL5, C3AR1, PSAP, GNG11, PF4, CCR2, GPR183, and CXCL16) are involved in the polarization of macrophages or the inflammatory response and may also be associated with the inflammatory regulation of pulmonary hypertension. This evidence concerns the gene C3AR1 and pulmonary arterial hypertension.