Immunohistochemical Detection of Interleukin-12 and Interferon-γ in Pigs Experimentally Infected with Mycoplasma hyopneumoniae

SummaryThe expression of interleukin-12 (IL-12) and interferon-gamma (IFN-γ) was examined immunohistochemically in the lungs of pigs aged 21 days infected experimentally with Mycoplasma hyopneumoniae (Mh). Ten pigs were inoculated intranasally with Mh and killed in pairs weekly from 7 to 35 days post-infection (dpi). Immunolabelling for IL-12 and IFN-γ was usually associated with inflammation, particularly in macrophages and lymphocytes in the thickened alveolar septa and in the hyperplastic bronchus-associated lymphoid tissue (BALT). Cells positive for both cytokines were detected at 7 dpi, their numbers increasing at 14 and 21 dpi, and slightly decreasing thereafter. The results suggest that IL-12 and IFN-γ play a role in pulmonary defence mechanisms against Mh infection.