Increased leukotriene B4 production, complement C3 conversion and acid hydrolase enzyme concentrations in different leucocyte sub-populations of dogs with atopic dermatitis

Various markers of the inflammatory response were measured in peripheral blood mononuclear cells (PBMCs) and polymorphonuclear neutrophils (PMNs) from 31 dogs with atopic dermatitis (AD). The variables assayed included chemiluminescence, acid hydrolase enzyme concentrations, leukotriene B4 (LTB4) production and complement C3 conversion. The results were compared to those derived from a population of clinically healthy dogs.Dogs with AD exhibited a significant increase in median LTB4 production in PMNs compared to controls (0.94 versus 0.00 ng/106 cells; P < 0.01). Significant increases in the median concentrations of intracellular β-galactosidase (PBMC fraction – 0.42 versus 0.25 mU/106 cells; P < 0.05) (PMN fraction – 0.47 versus 0.12 mU/106 cells; P < 0.01) and β-glucuronidase (PBMC fraction – 0.52 versus 0.27 mU/106 cells; P < 0.05) were also evident in the AD group. Although median maximum chemiluminescence values for both leucocyte sub-populations were higher in controls, the differences recorded were not significant (P > 0.05). However, the median time taken to reach maximum chemiluminescence was significantly shorter in the PMN fraction of dogs with AD (7.00 versus 10.00 min; P < 0.01). Atopic dogs had a significant increase in the median percentage conversion of complement C3 to C3b (66.0 versus 57.3%; P < 0.01). The results of this study indicate a priming of the inflammatory response in dogs with AD. The role of LTB4 in the pathogenesis of canine AD and the potential efficacy of leukotriene antagonists in the treatment of this disorder warrant further investigation.