When taking into account for the differences in cell numbers on overall cytotoxicity, by examining the product of CD56 cell numbers and lytic activity of the CD56+ cells from COPD subjects (which we have termed biological lytic activity) the significant differences remain (Figure 4B) and this inversely correlated with lung function, as assessed by FEV1 measurement (r = -0.75; p = 0.0098) (Figure 4C). Here, NCAM1 is linked to chronic obstructive pulmonary disease.