No difference in the percentage of CD56+ cells expressing NKG2D was observed when the subjects were stratified by FEV1 % predicted (Fig. 3B) or when subjects were analyzed categorically by COPD status (healthy smokers, n = 10; subjects with mild COPD, n = 5; subjects with severe COPD, n = 10; data not shown), which agrees with data from Borchers et al. [20]. This evidence concerns the gene KLRK1 and chronic obstructive pulmonary disease.