Lesional skin in atopic dogs shows a mixed Type-1 and Type-2 immune responsiveness.

Canine atopic dermatitis (AD) is a chronic inflammatory and pruritic skin disease which shares several characteristics with its human counterpart. In chronic patch test lesions of human with AD mainly a Th1-type cellular response is found. Besides, non-lesional AD skin is already skewed for inflammation and therefore different from healthy skin. The goal of this study was to characterize local immune responsiveness in chronic canine AD lesions as compared to that in non-lesional AD skin by defining T cell subset relevant cytokine- and transcription factor expression profiles. The gene expression of the Th1 cytokines IL-12p35, IL-12p40 and IFN-γ and their related transcription factors STAT4, SOCS5 and T-bet, the Th2 cytokines IL-4 and IL-13 and transcription factors STAT6, SOCS3 and GATA-3 and the regulatory cytokines IL-10 and TGF-β and the transcription factor FOXP3 was evaluated in healthy control and atopic dogs. In non-lesional (NLS) and chronic lesional skin (LS) of atopic dogs and control skin (CS) from healthy dogs mRNA expression of cytokines and transcription factors were measured by quantitative real-time PCR. Significantly different values were found for the following factors: IL-12p40 mRNA was lower in LS when compared to NLS. Expression of STAT4 was higher in LS compared to CS and NLS. More IL-13 and SOCS3 were found in LS and NLS when compared to CS and also in LS compared to NLS. GATA-3 was lower in LS compared to NLS. IL-10 expression was higher in both LS and NLS compared to CS and more IL-10 was present in LS compared to NLS. These findings indicate that both Th1- and Th2-type as well as T regulatory cells are present in NLS and LS in canine atopic skin.