Expansion of circulating follicular T helper cells associates with disease severity in childhood atopic dermatitis.

Follicular helper T (T) cells play crucial role in B-cell differentiation and antibody production. Although, atopic dermatitis (AD) is often associated with increased serum IgE levels, B-cell mediated responses have not been studied thoroughly. The aim of our study was to investigate the proportion of T-like cells in the disease. Twelve children and 17 adults with AD as well as 14 healthy controls were enrolled in the study. The frequency of CD4CXCR5ICOSPD-1 T-like cells and their IL-21 cytokine production were determined by flow cytometry. Immunohistochemical analysis was performed on skin biopsy specimens from AD patients for the detection of T markers. The percentages and absolute numbers of circulating T-like cells were significantly increased in children with AD compared to adult patients and healthy controls. IL-21 cytokine production of T-like cells was also elevated and showed a strong positive correlation with paediatric patients' SCORAD index. The expression of T-specific markers showed only a non-specific scattered pattern in skin biopsy specimens. This is the first study to demonstrate that T-like cells expanded in the peripheral blood of children with AD compared to adults. These results reinforce the importance of further investigations on T-like cells in different phenotypes and endotypes of AD.