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Expression of B7–1, B7–2, and Interleukin 12 in Bleomycin–Induced Pneumopathy in Mice

Background: The bleomycin–induced pneumopathy involves a T cell–mediated immune response. T cell activation requires both antigen/MHC recognition and costimulatory signals. The CD28 receptor on T cells with its ligand B7 represents one of the most important examples of this costimulation. Interleukin 12 (IL–12) has a strong synergistic effect with the B7–1/CD28 interaction on inducing proliferation and cytokine production in T cells. Methods: In this study, we investigated the expression of B7–1, B7–2, and IL–12 in bleomycin–induced pneumopathy in mice using reverse transcription polymerase chain reaction (RT–PCR), RT in situ PCR, and immunohistochemistry. Results: We observed concurrent upregulation of B7–1, B7–2, and IL–12p40 mRNA in the lung tissues at 1 h to 7 days after bleomycin instillation into the trachea. B7–1 mRNA and protein were found in bronchiolar epithelial cells as well as macrophages, B7–2 and IL–12p40 mRNA appeared to be expressed in mononuclear cells. Conclusions: These findings indicate that T cell–mediated immune response in this model involves the upregulation of B7–1, B7–2, and IL–12p40 mRNA, and also demonstrate the aberrant expression of B7–1 in bronchiolar epithelial cells.