TLR9 and chronic obstructive pulmonary disease: Similar findings were observed when analyzing exacerbated COPD (ECOPD) patients and the control group in a study by Alhabeeb et al. [35] where they found (C/C) and (T/C) genotypes and the allele C of TLR9 (T1237C) gene polymorphism were associated with a higher susceptibility risk for COPD.