CD2 and its ligands are involved in development and activation of MAIT cells

MAIT cells are innate-like T cells known for their semi-invariant TCR that recognizes vitamin B metabolites presented by MR1. While the involvement of TCR and cytokines in development and activation of MAIT cells is well documented, the contribution of co-receptors, including SLAM family receptors, remains poorly understood. This study revealed that CD2 and its ligands, CD48 in mice and CD58 in humans, were crucial for MAIT cell maturation and antigen-driven activation, but not for their responses to cytokines. Cis interactions of CD2 with its ligands on the same cell were essential for activation, with trans interactions contributing in some contexts. A natural subset of human MAIT cells lacking CD2 displayed reduced activation responses to antigen. Human CD48 recognized 2B4 rather than CD2, dampening TCR signal strength and activation of human MAIT cells. Thus, the interplay between CD2 and its ligands is pivotal for MAIT cell development and activation, highlighting potential approaches for treating human diseases implicating MAIT cells.