Cytokine mRNA expression in experimental porcine pneumonia

A porcine Pasteurella multocida (P. m.) infection model was established to study the spatial distribution of cytokine mRNA-expressing cells in lung tissue during acute pneumonia. The mRNA detection was performed by non-radioactive, formamide-free in situ hybridization (ISH) using oligonucleotides against the porcine interleukins (IL): IL-1beta, IL-2, IL-4, IL-6, IL-8, TNFalpha and TGFbeta. Cytokine mRNA-expressing macrophages were demonstrated by a double staining procedure combining immunohistochemistry (IH) using the primary antibody 2G6 with IL-1beta, IL-6 and TGFbeta ISH. With the exception of some stained TNFalpha-expressing cells, no IL mRNA was detectable in the lung of unaffected animals. The experimental P. m. pneumonia was characterized by a predominant, exudative and an additional proliferative interstitial component as well as abscess formation in the lung. Many cells of the region between the abscess membrane and the affected lung area showed high IL-6, IL-1beta, IL-4 as well as TGFbeta and few cells low IL-8 mRNA expression with characteristic distribution patterns. The ISH/IH double staining procedure revealed that at least some of the IL-6 or TGFbeta-producing cells belonged to the 2G6-positive macrophages