The median (interquartile range) GM-CSF+ and GM-CSFR+ cells/mm2 of submucosa was increased in severe asthma (1.4 (3.0) and 2.1 (8.4)) compared with those with mild to moderate asthma (0 (2.5) and 1.1 (5)) and healthy controls (0 (0.5) and 0 (1.6)), (p = 0.004 and p = 0.02, respectively). This evidence concerns the gene CSF2 and asthma.