Cystic fibrosis stem cells. Light micrograph of human embryonic stem cells containing the mutation for cystic fibrosis (CF). Stem cells are able to differentiate into other cell types (pluripotent). CF is an incurable hereditary disease that causes the lungs and pancreas to produce abnormally thick mucus. In the lungs, the thick mucus leads to severe respiratory problems and in the pancreas, the mucus blocks the release of digestive enzymes. This stem cell line was developed by Dr Stephen Minger of King's College, London, UK. In theory, the stem cells could be differentiated into lung epithelial cells which express the physical symptoms of cystic fibrosis. Such cells could then be tested with new drugs and treatments.