TLR2 and chronic obstructive pulmonary disease: AMs from exacerbation-prone COPD patients (29 patients, mean age 62 years, 21 males, FEV1% 57.6) are more refractory to TLR2 upregulation and cytokine induction by respiratory pathogens, compared with those from non-exacerbation-prone COPD patients (59 patients, mean age 58.1 years, 45 males, FEV1% 64.6) (36), indicating that COPD AMs with exacerbation have even more impaired function.