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

Follicular helper T (TFH) 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 TFH-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 CD4+CXCR5+ICOS+PD-1+ TFH-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 TFH markers. The percentages and absolute numbers of circulating TFH-like cells were significantly increased in children with AD compared to adult patients and healthy controls. IL-21 cytokine production of TFH-like cells was also elevated and showed a strong positive correlation with paediatric patients' SCORAD index. The expression of TFH-specific markers showed only a non-specific scattered pattern in skin biopsy specimens. This is the first study to demonstrate that TFH-like cells expanded in the peripheral blood of children with AD compared to adults. These results reinforce the importance of further investigations on TFH-like cells in different phenotypes and endotypes of AD.