Chronic obstructive pulmonary disease (COPD) small airway epithelial cells (SAECs) exert a delayed antimicrobial peptide (AMP) response to non-typeable Haemophilus influenzae (NTHi). mRNA expression of AMPs (DEFB1, DEFB4A (gene name for β-defensin 2 protein), CAMP, SLPI, S100A7, S100A8, S100A9, PI3) in non-COPD-derived (nC, grey) and COPD-derived (C, red) SAECs exposed to NTHi for 3 h or 24 h relative to PBS-exposed SAECs. Gene expression comparative crossing point change (ΔΔCp) is presented as a mean (n=11–18). Differences between NTHi and corresponding PBS-exposed SAECs were calculated with paired t-test; *: p<0.05, **: p<0.01, ***: p<0.001, ****: p<0.0001. Differences between means of non-COPD and COPD SAECs were calculated with a Mann–Whitney test; #: p<0.05.