IL21 and pulmonary alveolar proteinosis: In the PAP lesions, the two clusters are of equal size with IL-23, IL-9, IFNγ, IL-13, TNFα, IL-2, IL-17E, and IL-28A in the first cluster and GM-CSF, CCL20, IL-15, IL-10, IL-21, IL-6, IL-33, IL-27 in the second cluster.