Introduction of a method for detection of pro-inflammatory mediators in APP-infected porcine lungs by using immunohistochemistry and immunofluorescence

To better understanding the pathogenesis of Actinobacillus pleuropneumoniae (APP) infection in pigs, expression of cytokines and chemokines at the protein level was detected by immune-histochemical method (IHC) and method of immunofluorescence (IF) in different parts of the lungs of infected pigs. Production of pro-inflammatory mediators in the lungs is an important feature of APP infection. In this work we focused on pro-inflammatory cytokines IL-1beta, IL-6, IL-8 and TNF-alpha and chemokines CCL2, CCL4 and CXCL14. Four pigs were inoculated intranasally with APP infection, pigs were sacrificed according to the development of clinical signs of infection. Significant increase in cytokine expression of IL-8, less IL-1beta was detected in frozen-sections of necrotic areas (NA) of infected lungs, however expression of IL-6 and TNF-alpha in NA of the lungs was not detected. In the areas bordering on necrotic areas – marginal zone (MZ) and visually unaffected areas (UA) the pro-inflammatory cytokine levels were not significantly increased. Very low expression levels of CCL4 and CXCL14 were detected in the NA, no expression of chemokines in MZ and UA was detected.