Circulating CLA T cells in atopic dermatitis and their possible role as peripheral biomarkers.

Cutaneous lymphocyte-associated antigen (CLA ) T cells are specialized for skin homing and represent the main T-cell population in atopic dermatitis (AD) lesions. CLA is expressed on the surface of circulating CD45RO memory T cells and most skin-infiltrating T cells. Mechanistic studies and thus treatment advancements are limited by the need of large number of skin biopsies. Circulating CLA T cells may be a reliable surrogate marker of the inflammatory events occurring in the skin, and thus, the evaluation of CLA T cells in the blood may eliminate the need for skin biopsies. Preliminary work in AD has established that disease-associated T-cell abnormalities can be approached by either a study of skin lesions or activated CLA T-cell subsets in peripheral blood. Future studies in adults and children, across different skin disorders, correlating blood and skin phenotypes and determining skin-homing T-cell functional properties are needed to establish whether CLA memory subsets can be used as biomarkers and a substitute for skin biopsies. This review summarizes the latest advancements reached on circulating CLA in AD and the great potential they harbor in understanding AD mechanisms.