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Despite extensive structural studies elucidating how antigens are anchored to antigen-presenting molecules and presented to T cells, little is known about the display mechanism of the lipid-antigen-presenting molecule CD1c. Here, by combining structural immunology, lipidomics, and biophysical analysis, the authors reveal that the CD1c binding cleft accommodates two different lipids, one of them with a bulky headgroup positioned sideways for display to T cells, rather than upwards, different from the conventional upright antigen-presentation mode

Mucosal-associated invariant T (MAIT) cells express invariant TRAV1/TRAJ33 TCR-α gene segments and detect antigens presented by MR1. Here the authors show that atypical, MR1-restricted MAIT populations that include both Trav1⁺ and Trav1- cells are found in both Traj33-deficient mice and human peripheral blood.

Certain specific antigens have been shown to activate T cells in an MHC independent manner. Here the authors show a phycoerythrin reactive mouse TCR which recognises native protein and characterise the molecular nature of this interaction and that this specific TCR can be selected in the thymus.

Here the authors use single cell profiling of T cells across the human lifespan to show that a suboptimal TCR shift in T cells as we enter older age results in a molecular signature that resembles that of T cells from newborns and children.

In this study, Uldrich and colleagues describe the crystal structure of the Vγ9Vδ2 T cell antigen receptor (TCR) interacting with BTN2A1 and demonstrate the existence of a second ligand that co-binds to a distinct epitope on Vγ9Vδ2 TCR. Using these data, the authors suggest a model of Vγ9Vδ2 TCR activation in which BTN2A1 and BTN3A1 are tethered to each other at the steady state, and must disengage to allow TCR binding.

The invariant αβTCR of type I NKT cells recognizes a lipid α-GalCer presented by CD1d. Here the authors describe atypical α-GalCer-reactive NKT cells with diverse TCRs, which bind to CD1d-α-GalCer in a manner distinct from type I NKT cells, thus unveiling greater diversity in lipid antigen recognition.

Godfrey, Pellicci and colleagues define the developmental stages and checkpoints for the development of mucosal-associated invariant T cells in humans and mice.

Mucosal-associated invariant T cells recognize vitamin-B-derived ligands presented via the major-histocompatibility-complex-like molecule MR1. Rossjohn and colleagues demonstrate that these cells recognize a wide variety of ligands, some derived from common drugs, in an agonist or antagonist manner.

How γδ TCRs bind antigen presented by antigen-presenting molecules remains unclear. Godfrey and colleagues describe a population of human γδ T cells that interacts with CD1d and provide a molecular basis for how a γδ TCR binds CD1d–α-GalCer.

In a cohort of recovered patients with COVID-19, virus spike-specific antibodies were consistently elicited, but neutralizing activity was highly variable and inversely correlated with the proportion of CCR6⁺CXCR3⁻ spike-specific circulating follicular helper T cells.

Godfrey and colleagues review the basic biology, development, role in disease and immunotherapeutic potential of MAIT cells.