FPR2 and obstructive sleep apnea syndrome: FPR2 expression on NK cell was significantly increased in the very severe OSA patients versus the HS (12.94±1.75 vs. 9.13±1.98 MFI, p = 0.01, S2G Fig), and was negatively correlated with flow mediated dilatation percentage (r = -0.647, p = 0.012, S2H Fig).