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 o ut in 21 atopic subjects. Suppressive activity (SA) of sputum macrophages ( SMO) was investigated on autologous peripheral lymphocytes (APL) proliferat ion 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 n onreactive MC. Eosinophils and metachromatic cells correlated well (r = 0.6 442; 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 posit ive MC, while SMO showed SA in five with a negative MC. Only two patients w ith suppressive SMO had a positive MC. Cytokine profiles from five patients showed that two patients with a negative MC had interleukin (IL)-1 alpha a nd 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 wi th a borderline MC transcripted IL-5, but not IL-4. Conclusions: These data support the theory that patients with reduced suppr essive bronchial macrophages display clinical bronchial hyperreactivity.