Final answer:
Antibodies, also referred to as immunoglobulins, predominantly exist in the gamma globulin fraction of serum proteins, playing a key role in the body's immune defense mechanisms.
Step-by-step explanation:
Most antibodies are in the gamma globulin fraction of serum proteins. The gamma globulins, also known as immunoglobulins, are crucial for immune responses, protecting the body by binding to foreign objects such as bacteria and viruses.
These proteins are produced by specialized B lymphocytes and are present in both the blood and tissue fluids. Among the different plasma protein fractions, gamma globulins are specifically involved in immunity.