FC‐35 Real‐time evaluation of cytokine and protease expression in flea‐allergic and nonallergic dogs

Abstract

Flea bite allergy is a skin disorder with a complex immunopathogenesis. Th2 cytokines and proteases have been hypothesized to play a role in the pathogenesis. The aims of our study were to evaluate the cytokine and protease expression in skin biopsies and peripheral blood mononuclear cells (PBMC), the histopathological response, and the response to intradermal tests (IDT) in sensitized nonallergic and sensitized allergic dogs. Twenty dogs were exposed to fleas once a day for 4 days. Before flea exposure and after the last flea exposure, an IDT was performed, skin biopsies were taken, and PBMC were isolated. Skin biopsies and PBMC were stimulated with various substances, and real‐time RT‐PCR was performed using primers for tryptase, chymase, IL‐4, IL‐5, IL‐13, TNFα and IFNγ. Intradermal tests and histopathological examination of biopsies revealed much stronger reactions in the allergic group. Before flea exposure, mRNA expression of chymase, TNFα, IFNγ, IL‐5 and IL‐13 in biopsies of allergic dogs was higher compared to nonallergic dogs, whereas in PBMC only the expression of IFNγ was higher. After flea exposure, the difference in mRNA expression between allergic and nonallergic dogs was not as striking. In allergic dogs, stimulation of PBMC with flea antigen resulted in a higher expression of IL‐4 and IL‐13, whereas in biopsies only the expression of IL‐4 was higher. Our results demonstrate that even without the presence of antigen, the pattern of cytokine expression differs between allergic and nonallergic dogs. Furthermore, these results clearly demonstrate that the inflammatory response is much stronger in allergic dogs. Funding: Novartis SA.