Lymphocytic, cytokine and transcriptomic profiles in peripheral blood of dogs with atopic dermatitis

BACKGROUND Canine atopic dermatitis (cAD) is a common chronic and pruritic skin disease in dogs. The development of cAD involves complex interactions between environmental antigens, genetic predisposition and a number of disparate cell types. The aim of the present study was to perform comprehensive analyses of peripheral blood of AD dogs in relation to healthy subjects in order to determine the changes which would be characteristic for cAD. RESULTS The number of cells in specific subpopulations of lymphocytes was analyzed by flow cytometry, concentration of chosen pro- and anti-inflammatory cytokines (IL-4, IL-10, IL-13, TNF-α, TGF-β1) was determined by ELISA; and microarray analysis was performed on RNA samples isolated from peripheral blood nuclear cells of AD and healthy dogs. The number of Th cells (CD3(+)CD4(+)) in AD and healthy dogs was similar, whereas the percentage of Tc (CD3(+)CD8(+)) and Treg (CD4(+)CD25(+) Foxp3(+)) cells increased significantly in AD dogs. Increased concentrations of IL-13 and TNF-α, and decreased levels of IL-10 and TGF-β1 was observed in AD dogs. The level of IL-4 was similar in both groups of animals. Results of the microarray experiment revealed differentially expressed genes involved in transcriptional regulation (e.g., transcription factors: SMAD2, RORA) or signal transduction pathways (e.g., VEGF, SHB21, PROC) taking part in T lymphocytes lineages differentiation and cytokines synthesis. CONCLUSIONS Results obtained indicate that CD8(+) T cells, beside CD4(+) T lymphocytes, contribute to the development of the allergic response. Increased IL-13 concentration in AD dogs suggests that this cytokine may play more important role than IL-4 in mediating changes induced by allergic inflammation. Furthermore, observed increase in Treg cells in parallel with high concentrations of TNF-α and low levels of IL-10 and TGF-β1 in the peripheral blood of AD dogs point at the functional insufficiency of Treg cells in patients with AD.