FPR3 expression of NK T cell showed significant elevation after 1-year treatment in the COPD patients who had quit smoking, and were higher than that in those who continued smoking (3.5 ± 1.1 vs. 1.4 ± 1.2 MFI, p = 0.031, Fig. 3h). Here, FPR3 is linked to chronic obstructive pulmonary disease.