Peripheral natural killer cell subsets in atopic dermatitis

Background: Atopic dermatitis is a recurrent skin inflammatory disorder. Emerging literature supports a potential involvement of natural killer (NK) cells in the pathogenesis of this disease. In the peripheral blood, NK cell subsets harbor a distinct cell surface phenotype, which is influenced by the disease process. Objective: To investigate whether the frequency and cell surface phenotype of peripheral NK cells were altered in patients suffering from atopic dermatitis and the relationship between these changes and the clinical severity of the disease. Patients and methods: Peripheral blood mononuclear cells were isolated from 20 atopic dermatitis patients and 20 normal healthy individuals. Using flow cytometry, we analyzed the frequency of NK cells, the cell surface expression of several NK cell receptors, and their relation to the severity of atopic dermatitis, which was evaluated by measuring the SCORAD index. Results: The cell surface phenotype of various peripheral NK cells was significantly reduced in the peripheral blood of atopic dermatitis patients. A highly significant decrease was found in the CD3–CD56 dim subset in atopic dermatitis patients compared with controls. Moreover, the percentage of CD16^+ cells was found to be significantly reduced in the CD3–CD56 bright NK subset in atopic dermatitis patients compared with healthy controls. The reduction in the percentage of the CD3–CD56 dim subset was statistically correlated with the clinical severity of the disease as determined by the SCORAD score of atopic dermatitis. Conclusion: Atopic dermatitis is associated with quantitative and qualitative changes in the frequency and phenotype of peripheral NK cells, supporting the implication of these innate effectors in skin inflammation. The CD3–CD56 dim subset can be used as a marker for assessing atopic dermatitis severity.