Intravenous immunoglobulin-mediated expansion of regulatory T cells in autoimmune patients is associated with increased prostaglandin E2 levels in the circulation

CD4+FoxP3+ regulatory T cells (Tregs) are immunosuppressive cells that are critical for immune tolerance. Several studies have demonstrated that one of the anti-inflammatory mechanisms of action of intravenous immunoglobulin (IVIg) involves the expansion of Tregs. Recently, we demonstrated that IVIg-mediated Treg expansion involves the cyclooxygenase-2 (COX-2)-dependent induction of prostaglandin E2 (PGE2) in human dendritic cells (DCs). However, the validity of these findings in autoimmune patients is lacking. In this report, we demonstrate that the IVIg-mediated expansion of Tregs in autoimmune patients is associated with increased levels of circulatory PGE2. Due to its immunomodulatory effects on various immune cells, this increase in PGE2 represents one of the pathways by which IVIg exerts anti-inflammatory effects.