The antibody class that activates complement by the classic pathway is capable of crossing the placenta and possesses an Fc portion recognized by neutrophils and macrophages is IgM.

Question

Quizplus · Accepted Answer

The antibody class described is IgG, not IgM. IgG is the only antibody class that can cross the placenta, and it can activate complement by the classic pathway as well as possess an Fc portion recognized by neutrophils and macrophages. IgM is the first antibody to be produced in response to an antigen and can activate complement but does not cross the placenta.

The Antibody Class That Activates Complement by the Classic Pathway