Tuesday 3 March 2009, from 12.00 to 13.00
ULg, GIGA-R, Biochimie et Biologie Moléculaire
"The interstitial macrophage: a new piece in the asthma puzzle"
The respiratory tract is continuously exposed to both innocuous airborne antigens and immunostimulatory molecules of microbial origin such as lipopolysaccharide (LPS). LPS-stimulated lung dendritic cells (DCs) are endowed with the ability to induce T helper type 2 responses to inhaled antigens. However, only a minority of people exposed to environmental LPS develops allergic asthma. We have shown that LPS-triggered airway allergy is tightly controlled by lung interstitial macrophages (IMs), a cell population that remains largely uncharacterized. IMs may be distinguished from alveolar macrophages by their unique capacity to inhibit lung DC maturation and migration upon LPS stimulation, thereby preventing sensitization to concomitant aeroantigens. We have furthermore demonstrated that functional paralysis of LPS-stimulated DCs involves interleukin-10 production by IMs. Our results reveal a previously unknown role for IMs in regulating immune reactions and explain why the pulmonary immune system normally does not respond to harmless antigens in the presence of environmental LPS.