KIR2DL1 and chronic obstructive pulmonary disease: The numbers of CD158a+ and CD158b+ NK cells and CD158b+ NKT-like cells were greater in COPD patients, and the frequency of CD158b+ NK cells was negatively correlated with the forced expiratory volume in one second (FEV1)% prediction and the ratio of FEV1 to forced vital capacity (FVC).