We have CD four glycoproteins and we have CD eight glycoproteins. And the difference between these two different glycoproteins is their ability to bind to different types of major histocompatibility complexes. So let's begin with the CD four AlphaBeta T cell. So let's suppose we have the CD four T cell. And what that basically means is it contains a T cell receptor that contains an alpha unit shown in purple and the beta unit shown in red. And it also contains a special glycoprotein that extends from the cell membrane and that is shown in blue.