Structural determination of lipid antigens captured at the CD1d–T-cell receptor interface

Abstract

Glycolipid antigens recognized by αβ T-cell receptors (TCRs) drive the activation of invariant natural killer T (iNKT) cells, a specialized subset of innate T lymphocytes. Glycolipids with α-linked anomeric carbohydrates have been identified as potent microbial lipid antigens for iNKT cells, and their unusual α-anomeric linkage has been thought to define a “foreign” lipid antigen motif. However, mammals use endogenous lipids to select iNKT cells, and there is compelling evidence for iNKT cell responses in various types of sterile inflammation. The nature of endogenous or environmental lipid antigens encountered by iNKT cells is not well defined. Here, we sought to identify lipid antigens in cow’s milk, a prominent part of the human diet. We developed a method to directly capture lipid antigens within CD1d–lipid–TCR complexes, while excluding CD1d bound to nonantigenic lipids, followed by direct biochemical analysis of the lipid antigens trapped at the TCR–CD1d interface. The specific antigens captured by this “TCR trap” method were identified as α-linked monohexosylceramides by mass spectrometry fragmentation patterns that distinguished α- from β-anomeric monohexosylceramides. These data provide direct biochemical evidence for α-linked lipid antigens from a common dietary source.

Dual Modifications of α-Galactosylceramide Synergize to Promote Activation of Human Invariant Natural Killer T Cells and Stimulate Anti-tumor Immunity

“…In order to gain structural insights into the molecular recognition of AH10-7 in comparison to KRN7000, we generated complexes in vitro of mCD1d loaded with these glycolipids and co-crystallized them with the 2C12 i NKT cell T (Brennan et al, 2017; Pellicci et al., 2009; Wang et al, 2010) We used X-ray crystallography to determine the 3-dimensional structures of these ternary complexes to 3.2 Å resolution for AH10-7 and 2.6 Å for KRN7000 (Figure 5A, and Supplemental Table 1). In both complexes, the electron density at the molecular interface between the mCD1d-glycolipid complexes and the 2C12 i NKT TCR was unambiguous.…”

Miscarriage induced by adoptive transfer of dendritic cells and invariant natural killer T cells into mice

“…Our previous study showed that iNKT cells and DEC‐205 + DCs are accumulated in the decidua of women without aCAM who undergo late preterm birth . Various foods, herbal medicines, and drugs contain glycolipid antigens . Moreover, certain alarmins, HMGB1, uric acid, IL‐1α, and cell‐free DNA may be associated with the onset of pregnancy complications, miscarriages, preeclampsia, and preterm birth through the sterile pathway .…”

4“‐O‐Alkylated α‐Galactosylceramide Analogues as iNKT‐Cell Antigens: Synthetic, Biological, and Structural Studies

“…The a-anomeric configurationi sn oteworthy,a s the b-configuration is ac haracteristic feature of most mammalian glycolipids. [3] The mode of action of a-GalCer relies on ah igh-affinity bindinge ventw ith CD1d, am ajor histocompatibility complex (MHC)c lass I-like non-polymorphic glycoprotein associated with the membrane of antigen presenting cells (APCs). This binary a-GalCer-CD1d complex is presented to the semi-invariant ab T-cell receptor (TCR) of invariant natural killer T-cells (iNKT), ad istinct population of CD1d-restricted T-lymphocytes, to form at ernaryc omplex.…”

“…The α-anomeric configuration is noteworthy, since the β-configuration is a characteristic feature of most mammalian glycolipids. 3…”