Molecular computer graphic of an antibody-antigen complex. The antigen (red) is at top, with the antibody (blue) below. Part of the antibody, known as the antibody combining site, recognises & binds to a part of the antigen. The antigen shown is hen egg white lysozyme, which was injected into a mouse. In response, the mouse's immune system produced the appropriate antibody. Photographed by MM 23/7/88.