T cell activation requires antigen-specific engagement of the T-cell-receptor and additional antigen-independent costimulatory interactions. We investigated the role of the costimulatory molecules CD80/CD86 and OX40L in the immunopathogenesis of experimental Allergic Aspergillosis.

6-8 wk old female Balb/c mice were sensitized intraperitoneally and intranasally with Aspergillus fumigatus (Af) allergens. Animals were sensitized with Af along with recombinant interleukin-4 and sacrificed 24 hours after the last exposure to the antigen. Lung macrophages and B cells were collected and analyzed by flow cytometry for expression of the costimulatory molecules CD80, CD86 and OX40L. Peripheral blood eosinophils, total serum IgE, and allergen-specific IgG1 levels were also quantitated.

CD86 and CD80 molecules were upregulated on lung B cells in Af sensitized mice (51.3% CD80+ and 15.3% CD86+) as compared to normal controls (12% and 6.4%, respectively). Lung macrophages from allergic mice only expressed low levels of these molecules (1.58% CD86+ and 2.33% CD80+), but increased expression was observed when mice were co-injected with Af and rIL-4 (6.54% and 5.41%, respectively). OX40L expression was also upregulated on lung B cells (9.08% vs. 1.24%) and lung macrophages (4.23% vs. 1.47%) from Af-sensitized mice as compared to normal controls. Animals injected with Af-rIL-4 and Af also showed a marked increase (p<0.05) in peripheral blood eosinophils, total serum IgE, and allergen-specific IgG1 antibodies as compared to controls.

CD80, CD86 and OX40L costimulatory molecules are upregulated in response to Af allergens suggesting their involvement in the amplification of immunological and inflammatory responses during experimental Allergic Aspergillosis.