Comparison of circulating CD4, CD8 lymphocytes and cytokine profiles between dogs with atopic dermatitis and healthy dogs.

Introduction: Canine atopic dermatitis (cAD) is an inflammatory skin disease characterized by impaired immune function. Changes in the proportions of CD4 and CD8 lymphocytes and the serum concentrations of cytokines in the pathogenesis of cAD have been described.

Objectives: To assess whether the changes in the ratio of CD4 and CD8 lymphocytes in the peripheral blood of atopic dogs at the time of diagnosis are related to the severity of the disease. Furthermore, we determined whether the changes in the serum concentrations of the cytokines IL-31, IL-34, IL-10, IFN-γ, and TNF-α were different between atopic and control dogs.

Procedures: Fifty-six client-owned dogs with atopic dermatitis and 53 healthy control dogs were used. The percentages of CD4 and CD8 lymphocytes were determined by imaging flow cytometry. The index of CADESI-03 was calculated. Serum cytokine levels were analyzed using ELISA.

Results: Atopic dogs showed a higher percentage of CD8 lymphocytes, a lower CD4/CD8 ratio than healthy dogs, and a positive correlation with CADESI-03. Atopic dogs also showed higher serum IL-31 and IL-34 levels and lower IL-10 levels. A moderate positive correlation was found between serum IL-31 and CADESI-03.

Conclusions: The CD4/CD8 ratio may be a sensitive parameter that positively correlates with the severity of cAD, and elevated serum levels of IL-31 and IL-34 may facilitate diagnosis of the disease.