Many of the differences between airway niches and between health and CF that we aim to capture have been described previously, including in O2/CO2 levels, temperature,36 lysozyme,23 lactoferrin,23 polyamines,25,26 mucins,37 amino acids, carbon source content21 and salt concentrations.38 These media were designed to be cheap, accessible and readily modifiable, according to the research question being asked. The gene discussed is LTF; the disease is cystic fibrosis.