Although the proportions of NKG2C+ cells were similar in controls and COPD patients (13.9 ± 8.0 vs 14.4 ± 17.1, p = 0.9), higher values were observed in frequent than in occasional exacerbators (19.6 ± 20% vs. 10.5 ± 13, p < 0.05), albeit with a substantial dispersion of values (Fig. 4a). This evidence concerns the gene KLRC2 and chronic obstructive pulmonary disease.