RESULTS: CD4/CD8 double positive cells, representing cell-mediated immunity, were less abundant in IPA patients with COPD (0.81) compared with those with ILD (1.39) and NCFB (1.57) (p<0,001). In agreement, corticosteroid and broad-spectrum antibiotics were mostly used in individuals with COPD among all IPA patients (41/72, 57%). Immunoglobulin A (IgA) levels, which indicate humoral immunity, were lowest in IPA patients with NCFB (0.95), i.e. lower compared with IPA patients with COPD (1.64) and ILD (3.16) (p<0,001). Finally, secretory IgA (sIgA) levels were most abundant in bronchiectasis patients.