Final answer:
When anti-IgG binds to IgG, a lattice structure is formed, which is observable in in vitro precipitin reactions. Polyclonal antiserum, which binds to multiple epitopes, usually facilitates this lattice formation, as opposed to monoclonal antibodies that bind only to a single epitope.
Step-by-step explanation:
When Anti-IgG Binds to IgG
When anti-IgG binds to IgG, the resulting structure formed is known as a lattice. This occurs because each antibody, like anti-IgG, has two binding sites, which allows it to bind to two antigens. These antigens, in this case being IgG molecules, then become connected together through the antibodies. Consequently, as more antibodies bind to more antigens, a network or lattice structure is formed. This kind of reaction is often observable in in vitro tests, known as precipitin reactions, which typically utilize polyclonal antiserum capable of binding to multiple epitopes and thereby facilitating the lattice formation. However, with monoclonal antibodies, which bind to only a single epitope, lattice formation is much less likely to occur and thus a visible precipitin is not commonly observed.
In precipitin reactions, the visible antigen-antibody complex is referred to as a precipitin. Using solutions containing polyclonal antiserum favors the formation of such lattices over monoclonal antibodies because of their capability to bind multiple epitopes.