Enhanced killing activity of regulatory T cells ameliorates inflammation and autoimmunity.

Regulatory T cells (Treg) are pivotal suppressor elements in immune homeostasis with potential therapeutic applications in inflammatory and autoimmune disorders. Using Treg as vehicles for targeted immunomodulation, a short-lived Fas-ligand (FasL) chimeric protein (killer Treg) was found efficient in preventing the progression of autoimmune insulitis in NOD mice, and amelioration of chronic colitis and graft versus host disease. The main mechanisms of disease suppression by killer Treg are: a) in the acute phase induction of apoptosis in effector cells at the site of inflammation decreases the pathogenic burden, and b) persistent increase in FoxP3⁺ Treg with variable CD25 co-expression induced by FasL sustains disease suppression over extended periods of time. Reduced sensitivity of Treg to receptor-mediated apoptosis under inflammatory conditions makes them optimal vehicles for targeted immunotherapy using apoptotic agents.