Interleukin-4 production by human alveolar macrophages.
BACKGROUND
IL-4 is a key factor for T helper type 2 (Th2) differentiation and Ig class switching to IgE and IgG(4) during the development of immune responses. IL-4 is produced by T cells, mast cells, basophils, and eosinophils. However, there is also evidence suggesting that rat alveolar macrophages (AMs) produce IL-4.


OBJECTIVE
Given the importance of AMs and Th2-related diseases in the lung, we investigated the production of IL-4 by human AMs.


METHODS
Human AMs were isolated from bronchoalveolar lavage, purified, and IL-4 production was investigated at mRNA and protein levels using real-time PCR, flow cytometry, immunocytochemistry, and ELISA. The presence of IL-4 was investigated in subjects with asthma or asymptomatic airway hyper-responsiveness, and in normal non-smokers.


RESULTS
IL-4 and IL-4delta2 (a splice variant found in other IL-4 producing cells) mRNAs were found in all these subjects, but IL-4 expression could not be correlated with a particular disease. Protein production was verified by immunocytochemistry and flow cytometry analysis demonstrating, respectively, up to 69% and 59% positive AMs, regardless of the subject condition. Furthermore, phorbol-12-myristate-13-acetate and calcium ionophore stimulated the release of IL-4 after 48 h treatment in the presence of anti-IL-4 receptor antibody.


CONCLUSIONS
Our results show for the first time that IL-4 and IL-4delta2 mRNA are expressed and IL-4 protein produced and released by human AMs, suggesting a contribution of these cells in the modulation of Th2 immune response.
Pouliot
P
P
Centre de recherche, Hôpital Laval, Institut Universitaire de Cardiologie et de Pneumologie de l'Université Laval, Sainte-Foy, Québec, Canada.
Turmel
V
V
Gélinas
E
E
Laviolette
M
M
Bissonnette
E Y
EY
D001992:Bronchoalveolar Lavage Fluid / Q000166:cytology; D002478:Cells, Cultured; D005434:Flow Cytometry / Q000379:methods; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D015847:Interleukin-4 / Q000032:analysis / Q000096:biosynthesis / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism*; D009000:Monocytes / Q000276:immunology; D020033:Protein Isoforms / Q000032:analysis / Q000378:metabolism; D011650:Pulmonary Alveoli / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods
D020033:Protein Isoforms; D012333:RNA, Messenger; D015847:Interleukin-4