OX40 is a co-stimulatory immune checkpoint molecule that promotes the activation and the effector function of T lymphocytes through interaction with its ligand (OX40L) on antigen-presenting cells. OX40-OX40L axis plays a crucial role in Th1 and Th2 cell expansion, particularly during the late phases or long-lasting response. Atopic dermatitis is characterized by an immune dysregulation of Th2 activity and by an overproduction of proinflammatory cytokines such as interleukin (IL)-4 and IL-13. Other molecules involved in its pathogenesis include thymic stromal lymphopoietin, IL-33, and IL-25, which contribute to the promotion of OX40L expression on dendritic cells. Lesional skin in atopic dermatitis exhibits a higher level of OX40L+-presenting cells compared with other dermatologic diseases or normal skin. Recent clinical trials using antagonizing anti-OX40 or anti-OX40L antibodies have shown symptom improvement and cutaneous manifestation alleviation in patients with atopic dermatitis. These findings suggest the relevance of the OX40-OX40L axis in atopic dermatitis pathogenesis.
