Af–human host interaction spans asymptomatic immunization with detectable immunoglobulin G to Af, sensitization with detectable IgE to Af, through severe pulmonary or systemic diseases such as allergic bronchopulmonary aspergillosis (ABPA), chronic pulmonary aspergillosis, invasive aspergillosis, and chronic lung allograft disease (1). The gene discussed is IGHE; the disease is allergic bronchopulmonary aspergillosis.