Fig. 1

Overview of the role of LRBA in the interaction of antigen-presenting cells and T cells. To activate a T cell, an APC couples both its MHC with the TCR, and its CD28 cell surface molecule with the T cell's CD80/86 cell surface molecule. After activation of the TCR, CTLA-4 is trafficked to the T cell’s surface where it can also bind the APC’s CD28 molecule. In contrast to CD80/86, CTLA-4 downregulates the T cell’s activation by removing the CTLA-4/CD28-complexes from the cell surface. Once internalised, this complex is either degraded in lysosomes, or the CTLA-4 component is recycled thanks to the presence of LRBA and returned to the T cell’s surface allowing further downregulation. Abbreviations used: Ag: Antigen; APC: Antigen-presenting Cell; CD: Cluster of Differentiation; CTLA-4: Cytotoxic T lymphocyte Antigen 4; LRBA: Lipopolysaccharide-responsive Beige-like Anchor Protein; MHC: Major Histocompatibility Complex; TCR: T cell Receptor