Reactions involving IgG may need to be enhanced for which reason?

Reactions involving IgG may need to be enhanced for which reason?

• A. It is only active at 25°C.
• B. It may be too small to produce lattice formation.
• C. It has only one antigen-binding site.
• D. It is only able to produce visible precipitation reactions.

Answer: (B)

Lattice formation in precipitation reactions depends on cross-linking of antibodies and antigens into a network large enough to become visible as a precipitate. IgG is relatively small and has only two antigen-binding sites, so if the antigen is small or not sufficiently multivalent, cross-linking into a lattice can fail and no precipitate forms. Enhancing the reaction helps promote additional cross-linking and lattice growth, making the complexes large enough to precipitate. This can involve using multivalent antigens, increasing antibody or antigen concentrations, or adding bridging reagents that promote cross-linking. The other ideas aren’t accurate: IgG isn’t restricted to a single binding site, it isn’t limited to activity at 25°C, and IgG can participate in more than just visible precipitation under the right conditions.

Lattice formation in precipitation reactions depends on cross-linking of antibodies and antigens into a network large enough to become visible as a precipitate. IgG is relatively small and has only two antigen-binding sites, so if the antigen is small or not sufficiently multivalent, cross-linking into a lattice can fail and no precipitate forms. Enhancing the reaction helps promote additional cross-linking and lattice growth, making the complexes large enough to precipitate. This can involve using multivalent antigens, increasing antibody or antigen concentrations, or adding bridging reagents that promote cross-linking. The other ideas aren’t accurate: IgG isn’t restricted to a single binding site, it isn’t limited to activity at 25°C, and IgG can participate in more than just visible precipitation under the right conditions.