Uncovering Novel Mechanism of Immune Modulation of invariant Natural Killer T Cells by Liposomal α-Galactosylceramide
Author ORCID Identifier
Date of Graduation
Masters of Science (MS)
Jin Seon Im
Invariant Natural Killer T cells (iNK-T cells) are a powerful regulatory immune cell that can recruit both innate and adaptive immune cells. Unlike conventional T cells (CD4+ and CD8α+), they recognize glycolipid antigens via the MHC-class-I like molecule, CD1d. A synthetically derived glycolipid from the marine sponge, Agelas mauritianus, alpha-Galactosylceramide (α-GalCer) potently activates iNK-T cells. Within a few hours after activation, iNK-T cells produce high quantities of TH1 and TH2 type cytokines, thus shape subsequent adaptive immunity towards inflammation (TH1) or immune-suppression (TH2). Structural modification of α-GalCer’s phytosphingosine chain, α-GalCer C20:2 has been shown to polarize iNK-T responses towards TH2 and help treat several autoimmune diseases. Recently, Liposomal formulation of α-GalCer (RGI-2001) has been shown to help ameliorate Graft-Versus-Host-disease (GVHD) via expansion of regulatory T cells. However, molecular and cellular mechanism by which how Liposomal α-GalCer modulate iNK-T responses is unknown. Our preliminary data suggests that both TH2 biasing α-GalCer C20:2 and Liposomal α-GalCer elicit TH2 polarized iNK-T responses. We hypothesize Liposomal α-GalCer will display unique antigen uptake, processing and presentation with CD1d similar to known TH2 biasing α-GalCer analogues, allowing for an immunosuppressive cytokine response, thus reducing pro-inflammatory disease complications. In this study, we investigated the cellular and molecular requirements of CD1d association with Liposomal α-GalCer through various in vitro assays to assess antigen uptake, processing, and presentation to iNK-T cells. We found that Liposomal α-GalCer share kinetics of antigen association with CD1d likely within non-lipid raft domain in the antigen presenting cells, similarly to α-GalCer C20:2, but require cellular internalization for CD1d association, similarly to TH1 biasing α-GalCer. Our findings suggest that Liposomal aGalCer requires early endosomal recycling for association with CD1d. In the future, we plan to investigate the visual and kinetic sites of α-GalCer:CD1d loading using confocal microscopy, and impact on immunologic synapse formation.
CD1d restricted-invariant Natural Killer T cells, α-Galactosylceramide, liposomes, synthetic glycolipids