Blockade of Programmed Death-1 in Young (New Zealand Black × New Zealand White)F1 Mice Promotes the Activity of Suppressive CD8+ T Cells That Protect from Lupus-Like Disease

Abstract

The programmed death-1 (PD-1)/programmed death-1 ligand 1 (PD-L1) pathway regulates both stimulatory and inhibitory signals. In some conditions, PD-1/PD-L1 inhibits T and B cell activation, induces anergy, and reduces cytotoxicity in CD8+ T cells. In other conditions, PD-l/PD-L1 has costimulatory effects on T cells. We recently showed that induction of suppressive CD8+Foxp3+ T cells by immune tolerance of lupus-prone (New Zealand black × New Zealand white)F1 (BWF1) mice with the anti-DNA Ig-based peptide pConsensus (pCons) is associated with significantly reduced PD-1 expression on those cells. In this study, we tested directly the role of PD-1 by administering in vivo neutralizing Ab to PD-1 to premorbid BWF1 and healthy control mice. Anti–PD-1–treated mice were protected from the onset of lupus nephritis for 10 wk, with significantly improved survival. Although the numbers of T cells declined in aging control mice, they were maintained in anti–PD-1–treated mice, including CD8+Foxp3+ T cells that suppressed syngeneic CD4+CD25− T cell proliferation and IFN-γ production, reduced production of IgG and anti-dsDNA IgG, induced apoptosis in syngeneic B cells, and increased IL-2 and TGF-β production. The administration of anti–PD-1 Ab to BWF1 mice after induction of tolerance with pCons abrogated tolerance; mice developed autoantibodies and nephritis at the same time as control mice, being unable to induce CD8+Foxp3+ T suppressor cells. These data suggest that tightly regulated PD-1 expression is essential for the maintenance of immune tolerance mediated by those CD8+Foxp3+ T cells that suppress both Th cells and pathogenic B cells. PD-1 regulation could represent a target to preserve tolerance and prevent autoimmunity.