If you suspect a major deficiency of antibodies in a person, which of the following would you look for confirmatory evidence?

An antibody is a protein molecule produced in the living body which specifically inactivates an antigen. Chemically, antibodies are globular proteins which form about 17-20% of the total plasma proteins. They are also called immunoglobulins (Ig). A deficiency of antibodies would manifest as a decrease in serum globulins, specifically the gamma globulins which contain most of the antibodies. Therefore, to confirm a major deficiency of antibodies, one would look for low levels of serum globulins.