Treatment with oclacitinib, a Janus kinase inhibitor, down-regulates and up-regulates CD25 and Foxp3 expression, respectively, in peripheral blood T cells of dogs with atopic dermatitis

The findings of the study strongly suggest that: (a) in terms of the impact of OCL on the number of PB CD4⁺ and CD8⁺ T cells, monthly treatment with the drug should be considered as a relatively safe; (b) the eosinophil-reducing effect and the down-regulation of the AD up-regulated CD25 expression on CD4⁺ Teff cells may constitute significant elements of the mechanism of action underlying the therapeutic effects of the drug in the treatment of canine AD; (c) the generation of inducible Foxp3-expressing CD4⁺ regulatory T cells - resulting in the shift of the CD4⁺ Treg cell (i.e. Foxp3⁺CD4⁺)/activated Teff (i.e. CD25⁺CD4⁺) cell balance toward an increased proportion of Treg cells - may be considered as additional mechanism involved in producing the immunomodulatory/immunosuppressive properties of OCL.