Correlation between clinical findings, mast cell count and interleukin 31 immunostaining in the skin of dogs with atopic dermatitis

ABSTRACT: In this study the correlation between the clinical score, mast cell count and interleukin 31 (IL-31) immunostaining in the skin of dogs with atopic dermatitis was determined. A total of 31 dogs of different breeds, from one to eight years of age, were chosen for the study. The 20 females and 11 males were categorized based on the CADESI-4 system, as having discrete, moderate or marked atopic dermatitis. Skin samples were collected from the axillary and interdigital regions and stained with hematoxylin and eosin for cytohistomorphological analyses and toluidine blue to evaluate the mast cell counts, and immunohistochemistry for the IL-31 immunostaining. Animals revealing higher atopic dermatitis scores had greater numbers of mast cells and IL-31 immunolabeled cells. More numbers of cells immunolabeled for IL-31 were evident in the axillary skin compared with the interdigital skin in dogs having this condition. A correlation was identified between the clinical scores and mast cell numbers in the interdigital region, as well as between the clinical scores and number of cells immunolabeled for IL-31 in the axillary area. A correlation was also reported between the mast cell numbers and IL-31 immunolabeled cells only in the axillary skin, and none in the interdigital regions. It was thus concluded that the mast cells and IL-31 are involved in the pathogenesis of the canine atopic dermatitis (CAD), as well as lymphocytes and plasma cells. It was also observed that the higher the degree of clinical severity of the disease, the more the numbers of mast cells and IL-31 in the skin of those animals suffering from CAD, which implies the influence of these immunological constituents on the genesis of pruritus and disease progression.