Does the fact that sIgA does not activate complement make it less effective in preventing infection than IgG? Explain how the structure of an antibody is designed to facilitate the function of the...

Does the fact that sIgA does not activate complement make it less effective in preventing infection than IgG?

Explain how the structure of an antibody is designed to facilitate the function of the particular antibody, e.g., why an antibody has at least two active sites, why it has an Fc portion, and why it might be cross-linked as multimers.