In BAL fluid, the total cell count, percentages of neutrophils and eosinophils, and percentage of mast cells — this last having the greatest discriminating power — tend to be higher in hypersensitivity pneumonitis than in sarcoidosis, whereas the CD4/CD8 T-cell ratio tends to be above normal in sarcoidosis and below normal in hypersensitivity pneumonitis (80, 127). The gene discussed is CD8A; the disease is hypersensitivity pneumonitis.