Figure 6.

Simplified diagram of anti-idiotype antibody formation. A variable part of the antibody (Ab1) able to bind to the Spike is called idiotype. Since this part is a “new” protein within the repertoire of antigens known to the immune system, the latter produces antibodies (Ab2) in response to the idiotype, which can recognise and bind to it. These secondary antibodies, called “anti-idiotype”, represent in a certain way the internal image of the external antigen (Spike) and may share some of its biological properties. * Molecular complementarity of idiotypes.