Increased expression of the CD80 accessory molecule by alveolar macrophages in asthmatic subjects and its functional involvement in allergen presentation to autologous TH2 lymphocytes

Background: Alveolar macrophages (AMs) are more efficient antigen-presenting cells in allergic individuals than in nonatopic subjects. Objective: We studied whether this difference may be correlated to increased expression of membrane costimulatory molecules, such as the B7 molecules (CD80 and CD86). Methods: Eleven subjects with allergic asthma sensitized to Dermatoplagoides pteronyssinus and 5 healthy nonatopic volunteers underwent bronchoalveolar lavage, and the costimulatory molecule expression on AMs was evaluated. Peripheral blood T cells, either freshly isolated or as established D pteronyssinus-specific cell lines, were cultured with autologous monocytes or AMs as antigen-presenting cells. In vitro allergen-induced proliferation and cytokine production were evaluated in the presence of B7-blocking reagents. Results: Allergic individuals had a significantly higher proportion of AMs expressing the CD80 molecule than control subjects (28.5% +/- 14.8% vs 1.4% +/- 1.2%; P < .001), whereas no difference was observed in CD86 expression (2.0% +/- 2.3% vs 1.1% +/- 0.6; P > .1). In a large proportion of the asthmatic subjects we studied, AMs were presenting soluble antigens (tetanus toroid and streptolysin-O) to freshly isolated T cells more efficiently than AMs from nonatopic control subjects. Finally, both T-cell proliferation and cytokine production of D pteronyssinus-specific established T-cell lines were inhibited by a CD80-blocking antibody in a dose-dependent manner. Conclusion: Costimulation by means of CD80 expressed by AMs is probably involved in the amplification of the allergen-specific T-lymphocyte response in the airways of asthmatic subjects.