A significant increase in the percentage of CD28nullCD8+ T and NKT-like cells producing IFNγ and TNFα compared with CD28 + CD8+ T and NKT-like cells was noted in COPD patients and control groups (data for CD28null and CD28+ CD8+ and CD8− T and NKT-like cells producing IFNγ for the COPD group shown in Fig. 2) (data for IFNγ and TNFα production for the control group and TNFα production by the COPD group not shown). Here, CD28 is linked to chronic obstructive pulmonary disease.