LEP and chronic obstructive pulmonary disease: In addition, we found that serum levels of AK155(IL-26) have a negative correlation with FEV1% and FEV/FVC and a positive correlation with CRP and BMI in exacerbated and stable COPD patients; these matched results found by Savchenko et al. [50] who showed that AK155(IL-26) levels in sputum have a positive correlation with CRP, BMI, and leptin and have a negative correlation with FEV1% and FEV/FVC.