Crystal Structure of CD28
Ribbon representation of the structure of the CD28 IgSF domain (top left) and its alpha carbon trace (red) compared to the related costimulatory molecules CTLA-4 (blue) and PD-1 (purple; top right) and archetypal antigen receptor (TCRd, grey) and adhesion molecule V-set domains (B7-1, light blue; bottom); two orthogonal views are shown. The costimulatory receptor IgSF domains appear to be more structurally related to antigen receptor V-set domains than those from adhesion molecules.