Mature CD11c(+) cells are enhanced in hypersensitivity pneumonitis

The present study verified the hypothesis that enhanced maturation of antigen-presenting CD11c(+) cells could explain the viral-induced exacerbated immune response to Saccharopolyspora rectivirgula (SR), the main antigen responsible for farmer's lung, a classic form of hypersensitivity pneumonitis (HP). Four groups of mice were studied: group 1 received intranasal instillations of saline; group 2 received instillations of SR for 12 weeks; group 3 received instillations of saline and a single infection with Sendai virus on week 3; and group 4 received instillations of SR for 12 weeks with a single administration of Sendai virus on week 3. On week 13, mice were sacrificed and bronchoalveolar lavage was performed. Lungs were harvested, digested with enzymes, and CD11c(+) cells were analysed in flow cytometry with anti-CD11c, anti-CD86 and anti-major histocompatibility complex class II markers. Immunofluorescence studies were also performed with the same cell surface markers. Both flow cytometry and immunofluorescence results demonstrate that mature CD11c(+) cells are significantly enhanced in SR-challenged mice simultaneously infected with Sendai virus, compared with other groups. These CD11c(+) cells persist in the lung for 9 weeks after the virus infection. Maturation of CD11c(+) cells could explain, at least in part, the virus-induced increased immune response to SR antigens in this model of HP, but mechanisms have still to be elucidated.