CD137 and CD137L signals are main drivers of type 1, cell-mediated immune responses

Abstract

ABSTRACT: CD137 is expressed on activated T cells and NK cells, among others, and is a potent co-stimulator of antitumor immune responses. CD137 ligand (CD137L) is expressed by antigen presenting cells (APC), and CD137L reverse signaling into APC enhances their activity. CD137–CD137L interactions as main driver of type 1, cell-mediated immune responses explains the puzzling observation that CD137 agonists which enhance antitumor immune responses also ameliorate autoimmune diseases. Upon co-stimulation by CD137, Th1 CD4+ T cells together with Tc1 CD8+ T cells and NK cells inhibit other T cell subsets, thereby promoting antitumor responses and mitigating non-type 1 auto-immune diseases.