LAG3 Regulates T Cell Activation and Plaque Infiltration in Atherosclerotic Mice

The immune checkpoint receptor lymphocyte-activation gene 3 (LAG3) is a new target for immune checkpoint blockade (ICB), but the effects of LAG3 on atherosclerosis are not known. The aim of the study was to evaluate the role of LAG3 on plaque inflammation using murine hypercholesterolemic models of atherosclerosis. To study the role of LAG3 in atherosclerosis, we investigated both bone marrow chimeras lacking LAG3 in hematopoietic cells as well as global Lag3-/- knockout mice. Effects of anti-LAG3 monoclonal antibody monotherapy and combination therapy with anti-programmed cell death protein 1 (PD-1) were tested in hypercholesterolemic low-density lipoprotein receptor knockout (Ldlr-/-) mice and evaluated by histology and flow cytometry. LAG3-deficiency or treatment with blocking anti-LAG3 monoclonal antibodies led to increased levels of both interferon gamma–producing T helper 1 cells and effector/memory T cells, balanced by increased levels of regulatory T cells. Plaque size was affected by neither LAG3 deficiency nor LAG3 blockade, although density of T cells in plaques was 2-fold increased by loss of LAG3. Combination therapy of anti-PD-1 and anti-LAG3 had an additive effect on T cell activation and cytokine production and promoted plaque infiltration of T cells. Loss of LAG3 function promoted T cell activation and accumulation in plaques while not affecting plaque burden. Our report supports further clinical studies investigating cardiovascular risk in patients treated with anti-LAG3 ICB.