Whilst sputum SPLUNC1 protein levels were reduced in asthma, CF and non-CF bronchiectasis [16,21,22,39,41], SPLUNC1 was unchanged in chronic obstructive pulmonary disease (COPD) patients at mRNA and protein levels (both cellular and secreted into sputum) [5]. This evidence concerns the gene BPIFA1 and cystic fibrosis.