PD-1/PD-L Blockade Prevents Anergy Induction and Enhances the Anti-Tumor Activities of Glycolipid-Activated Invariant NKT Cells

Abstract

Invariant NKT (iNKT) cells recognize glycolipid Ags, such as the marine sponge-derived glycosphingolipid ␣-galactosylceramide (␣GalCer) presented by the CD1d protein. In vivo activation of iNKT cells with ␣GalCer results in robust cytokine production, followed by the acquisition of an anergic phenotype. Here we have investigated mechanisms responsible for the establishment of ␣GalCer-induced iNKT cell anergy. We found that ␣GalCer-activated iNKT cells rapidly up-regulated expression of the inhibitory costimulatory receptor programmed death (PD)-1 at their cell surface, and this increased expression was retained for at least one month. Blockade of the interaction between PD-1 and its ligands, PD-L1 and PD-L2, at the time of ␣GalCer treatment prevented the induction iNKT cell anergy, but was unable to reverse established iNKT cell anergy. Consistently, injection of ␣GalCer into PD-1-deficient mice failed to induce iNKT cell anergy. However, blockade of the PD-1/PD-L pathway failed to prevent bacterial-or sulfatide-induced iNKT cell anergy, suggesting additional mechanisms of iNKT cell tolerance. Finally, we showed that blockade of PD-1/PD-L interactions enhanced the antimetastatic activities of ␣GalCer. Collectively, our findings reveal a critical role for the PD-1/PD-L costimulatory pathway in the ␣GalCer-mediated induction of iNKT cell anergy that can be targeted for the development of immunotherapies.

α-Galactosylceramide but Not Phenyl-Glycolipids Induced NKT Cell Anergy and IL-33–Mediated Myeloid-Derived Suppressor Cell Accumulation via Upregulation of egr2/3

“…These phenomena were not observed in our phenyl-glycolipids, which had been reported to have greater TCR signaling than a-GalCer because of stronger binding avidity and greater binding stability of CD1d-phenyl glycolipid complexes for iNKT TCR (8). Our findings were in line with the report that a-GalCer induced the expression of PD1 and cbl-b, which might contribute to NKT cell anergy (9,12). It was also consistent with the reports that egr2/3 could regulate the expression of PD1 and cbl-b (41) to cause T cell tolerance.…”

“…Parekh et al (9) reported that administration of a-GalCer induced expression of programmed death 1 (PD1) on NKT cells, which contributed to NKT cells anergy. PD1 is a member of the costimulatory molecules CD28 family and is expressed on activated T, B, NKT cells, monocytes, and dendritic cells but not on naive T cells (10).…”

Mucosal-Associated Invariant T Cell Deficiency in Systemic Lupus Erythematosus

“…In conventional T cells, PD-1 is not expressed on naive T cells, but it is inducibly expressed after T cell activation (36). In recent reports, PD-1 and its ligands have been implicated in the induction and maintenance of T cell and NKT cell anergy (37,38,42,43). In our previous report, we demonstrated that NKT cell dysfunction was associated with upregulation of inhibitory receptor PD-1 in active tuberculosis, and it was partially recovered by blockade of PD-1 (44).…”

“…Moreover, recent reports have shown that PD-1-PD-L interaction is involved in the induction and maintenance of NKT cell anergy (37,38). To determine whether MAIT and NKT cell dysfunctions are related to PD-1, we examined the expression levels of PD-1 in the peripheral blood samples of 11 SLE patients, 10 RA patients, and 10 HCs (Fig.…”

Targeted Delivery of α-Galactosylceramide to CD8α+ Dendritic Cells Optimizes Type I NKT Cell–Based Antitumor Responses

“…Strikingly, whereas free a-GalCer induced iNKT cell hyporesponsiveness, iNKT cells from mice previously inoculated with a-GalCer-loaded DCs maintained their capacity to reactivate. Of note, free a-GalCer induced enhanced PD-1 expression on iNKT cells, an inhibitory molecule that causes iNKT cell hyporesponsiveness (32,33), whereas a-GalCer-loaded DCs failed to do so (Fig. 1C).…”