Total RNA will be extracted from the cellular content of the induced sputum plug using a combination of Trizol extraction and Qiagen RNeasy spin columns in a similar way to previously described12. Quantitative RT-PCR, using previously developed primers and probes, will be used to determine the relative quantities of mRNA of MMPs and TIMPs as described12. We remain the only centre in the world to routinely profile the entire MMP and TIMP gene family in human samples. This gives an all encompassing view of the involvement of these enzymes and inhibitors in the disease process and also sheds light on potential new biomarkers. The possibility of expanding the gene profiling without the need for additional sputum collection also adds value to the research. This might include other proteinase families with roles in ECM breakdown or in inflammation.