Real-time RT-PCR quantification of mRNA encoding cytokines, CC chemokines and CCR3 in bronchial biopsies from dogs with eosinophilic bronchopneumopathy

Idiopathic canine eosinophilic bronchopneumopathy (EBP) is a disease characterized by eosinophilic infiltration of the pulmonary interstitium and bronchial mucosa, a cause for which has not yet been discovered. A recent study, examining the relative proportion of various lymphocyte cell subsets within bronchoalveolar lavage fluid from dogs with EBP, has shown a selective increase in CD4+ T-cells and a selective decrease in CD8+ T-cells, suggesting that a similar Th2 immune response might occur in EBP. The aim of the present study was to determine the profile of cytokine, chemokine and CC chemokine receptor 3 (CCR3) messenger RNA (mRNA) expression in bronchial tissue from dogs with EBP. Real-time RT-PCR assays were used for the quantification of mRNA encoding for a panel of cytokines, CC chemokines and CCR3 in perendoscopic bronchial biopsies from eight dogs with EBP and seven age-matched control dogs. Messenger RNA transcribed from the housekeeping gene glyceraldehyde-3-phosphate dehydrogenase was used for normalisation of the threshold cycle in order to determine the relative copy numbers of the transcripts. No significant difference in the expression of any cytokine, MCP-1, -2, -4 and CCR3 was found between control and EBP dogs. The expression of transcript for MCP-3, eotaxin-2 and -3 was significantly greater in bronchial biopsies from dogs with EBP than in samples from control dogs while there was significantly less mRNA encoding RANTES in the mucosa of dogs with EBP. In conclusion, the cytokine mRNA expression profile in perendoscopic bronchial biopsies is similar in dogs with EBP and dogs without respiratory disease. Further studies on the quantification of mRNA encoding cytokines in isolated T lymphocytes from bronchoalveolar lavage fluid or bronchial biopsies are needed before any conclusion on the cytokine profile in canine EBP can be drawn. Eotaxin-2, -3 and MCP-3 appear to be implicated in the pathogenesis of the disease.