What function does IgG NOT perform?

IgG has several important functions in the immune response, which include neutralizing toxins, opsonization, and providing immunity to newborns through placental transfer. However, while IgG can activate the complement system, this is not its primary or most efficient role.

The complement system is a group of proteins that work together to enhance the ability of antibodies and phagocytic cells to clear pathogens. IgG can activate the classical pathway of complement, but other immunoglobulin classes, particularly IgM, are far more efficient at initiating this pathway because of their structure and the ability to simultaneously bind multiple complement proteins.

Therefore, the choice indicating that IgG does not primarily perform the function of activating complements is accurate, reflecting the lesser role it plays in this specific process compared to its other functions.