Suppressive activity of bronchial macrophages recovered by induced sputum

Background: The immunomodulatory activity of macrophages was shown to be a crucial mechanism in the pathogenesis of asthma. Methods: Induced sputum (IS) and methacholine challenge (MC) were carried out in 21 atopic subjects. Suppressive activity (SA) of sputum macrophages (SMO) was investigated on autologous peripheral lymphocytes (APL) proliferation in 12 of these patients and compared to the MC. Results: In 10 of the 21 patients, the FEV1 was >80%; five of these had a nonreactive MC. Eosinophils and metachromatic cells correlated well (r = 0.6442; P = 0.0029), but not with the MC. The SA of SMO correlated (P = 0.0152) with the MC: SMO enhanced APL proliferation in five patients with a positive MC, while SMO showed SA in five with a negative MC. Only two patients with suppressive SMO had a positive MC. Cytokine profiles from five patients showed that two patients with a negative MC had interleukin (IL)-1 alpha and beta, IL-6, and transforming growth factor (TGF)-beta transcripts, while two patients with a positive MC transcripted IL-4 and IL-5. One patient with a borderline MC transcripted IL-5, but not IL-4. Conclusions: These data support the theory that patients with reduced suppressive bronchial macrophages display clinical bronchial hyperreactivity.