Programmed death ligand-1 expression on donor T cells drives graft-versus-host disease lethality

Programmed death ligand-1 (PD-L1) interaction with PD-1 induces T cell exhaustion and is a therapeutic target to enhance immune responses against cancer and chronic infections. In murine bone marrow transplant models, PD-L1 expression on host target tissues reduces the incidence of graft-versus-host disease (GVHD). PD-L1 is also expressed on T cells; however, it is unclear whether PD-L1 on this population influences immune function. Here, we examined the effects of PD-L1 modulation of T cell function in GVHD. In patients with severe GVHD, PD-L1 expression was increased on donor T cells. Compared with mice that received WT T cells, GVHD was reduced in animals that received T cells from Pdl1–/– donors. PD-L1–deficient T cells had reduced expression of gut homing receptors, diminished production of inflammatory cytokines, and enhanced rates of apoptosis. Moreover, multiple bioenergetic pathways, including aerobic glycolysis, oxidative phosphorylation, and fatty acid metabolism, were also reduced in T cells lacking PD-L1. Finally, the reduction of acute GVHD lethality in mice that received Pdl1–/– donor cells did not affect graft-versus-leukemia responses. These data demonstrate that PD-L1 selectively enhances T cell–mediated immune responses, suggesting a context-dependent function of the PD-1/PD-L1 axis, and suggest selective inhibition of PD-L1 on donor T cells as a potential strategy to prevent or ameliorate GVHD

Regulation of Lcn2 mRNA expression and secretion by cytokines in adipocytes.

<p>(A) the mRNA expression of Lcn2 in 3T3-L1 adipocytes treated with TNFα, IL-1β, or IL-6 at the concentration of 1 nM for 16 h. The mRNA expression levels in cytokine-treated adipocytes were normalized to the levels in control adipocytes and shown as fold changes. The results are presented as mean ± SE and represent two independent experiments. ** p<0.01, *** p<0.001; * Comparison between control and treated cells. (B) Lcn2 secretion in 3T3-L1 adipocytes treated with TNFα, IL-1β, or IL-6 at the concentration of 1 nM for 24 h. Conditioned media were collected and subjected to immune-blotting with the antibody against Lcn2. The results represent two independent experiments. (C) Western-blotting of Lcn2 in 3T3-L1 adipocytes treated with cytokines under the non-reducing condition.</p

The Lcn2 expression in adipose tissue depots and liver during metabolic stress.

<p>(A) the mRNA expression of Lcn2 in brown adipose tissue (BAT), epididymal adipose tissue (Epi), inguinal adipose tissue (Ing), and liver in C57/BL6 mice at 12 weeks of age during 48 h fasting. (B) Lcn2 protein expression in BAT, Epi and Ing adipose tissue in C57/BL6 mice at 12 weeks of age during 24 h fasting. (C) the mRNA expression of Lcn2 in BAT, Epi and Ing adipose tissue, and liver in C57/BL6 mice at 12 weeks of age after exposed to 22°C or 4°C for 4 h. (D) Norepinephrine induces Lcn2 expression and secretion in 3T3-L1 adipocytes. 3T3-L1 cells on day 7 of differentiation were treated with or without 1 µM norepinephrine (NE) for 24 h. Conditioned media and cells were collected and subjected to immune-blotting with the antibody against Lcn2. The mRNA expression levels in fasted and cold-adapted mice were normalized to the levels in control mice and shown as fold changes. The results are presented as mean ± SE and represent two independent experiments (n = 4–6 in each experiment). * p<0.05, ** p<0.01; * Comparison between control and fasted or cold-exposed mice.</p

Effect of fatty acids on Lcn2 expression and secretion in adipocytes.

<p>3T3-L1 adipocytes on day 7 of differentiation were treated with 100 µM BSA with or without (A) 250 µM palmitate, 400 µM oleate, (B) 400 µM EPA, or (C) 10 µM phytanic acid in low-glucose media in the presence of insulin. After 24 h, conditional media and cells were collected and subjected to western-blotting with the antibody against Lcn2. The results represent for two independent experiments.</p