The dashed line represents the detection limit. (C) Total CD8+, GrB and IFNγ expressing T cells in BAL fluid were measured using flow cytometry. (D) IFNγ protein levels in BAL fluid were measured by ELISA. (E) Total CD8+, GrB and IFNγ expressing T cells in lung parenchyma were measured using flow cytometry. (F) Virus specific antibody titers in serum were determined via a hemagglutination inhibition (HAI) assay.