CD8A and hypersensitivity pneumonitis: Unexpectedly, we found that the combination of viable A. niger spores and high-dose LPS reproduces key features of acute HP including the lack of airway hyperreactivity and eosinophilia; substantial neutrophilia; enhanced CD8+ cytotoxic T cells recruitment; and reduced or absent TH2 and predominant TH1 and TH17 cytokines.