ALDH7A1 and hypersensitivity pneumonitis: Sera from 8 patients with BRHP (2 acute, 6 chronic), 2 with summer-type HP (SHP), 2 with humidifier lung (HL), and 3 healthy volunteers (HV) were screened by 1-DE immunoblotting of pigeon serum (Fig. 1a), pigeon intestine homogenate and PDE (Fig. 1b).