Lack of host lung tissue expression of IFN-γ–inducible B7-H1 contributed to Th2-mediated idiopathic pneumonia. (A) Intracellular cytokine profiles of splenic CD4⁺ T cells 10 days after HCT. Gated CD4⁺ T cells are shown in CD4 versus cytokines. Representative of 4 replicate experiments is shown. (B-C) Percent survival and body-weight change of recipients after HCT. There were 12 mice in each group, combined from 3 replicate experiments. (D) Mean ± SE of histopathology scores (n = 6). (E) Ten days after HCT, cells from lungs of recipients were stained for CD45, CD11c, and B7-H1 or isotype control. Gated CD11c⁺ or CD45⁻ cells were shown in histogram for B7-H1 or isotype control. Representative of 3 replicate experiments is shown. (F) Immunohistochemical staining of B7-H1 in lung tissues harvested 6 days after HCT. One representative picture of 3 replicate experiments is shown. (G-H) IFN-γ^−/− or IFN-γR^−/− donor cells were transplanted into B7-H1^−/−, or B7-H1^−/− chimera recipients. Percent survival curves are shown. There were 6 to 8 mice in each group, combined from 2 replicate experiments. (I) IFN-γR^−/− donor cells were transplanted into WT, B7-H1^−/−, or B7-H1^−/− chimera recipients. Mean ± SE of histopathology scores is shown (n = 6). (J) IFN-γ^−/− donor cells were transplanted into WT or B7-H1^−/− recipients with or without injection of recombinant IFN-γ. Mean ± SE of histopathology scores is shown (n = 6).