EXPRESSION OF B7-1, B7-2, AND INTERLEUKIN-12 IN BLEOMYCIN-INDUCED PNEUMONOPATHY IN MICE

Background: The bleomycin-induced pneumopathy involves a T cell-mediat ed immune response. T cell activation requires both antigen/MHC recogn ition and costimulatory signals. The CD28 receptor on T cells with its ligand B7 represents one of the most important examples of this costi mulation. Interleukin 12 (IL-12) has a strong synergistic effect with the B7-1/CD28 interaction on inducing proliferation and cytokine produ ction in T cells. Methods: In this study, we investigated the expressi on of B7-1, B7-2, and IL-12 in bleomycin-induced pneumopathy in mice u sing reverse transcription polymerase chain reaction (RT-PCR), RT in s itu PCR, and immunohistochemistry. Results: We observed concurrent upr egulation 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 macroph ages, B7-2 and IL-12p40 mRNA appeared to be expressed in mononuclear c ells. Conclusions: These findings indicate that T cell-mediated immune response in this model involves the upregulation of B7-1, B7-2, and I L-12p40 mRNA, and also demonstrate the aberrant expression of B7-1 in bronchiolar epithelial cells.