Antibodies are proteins produced by the immune system in response to the presence of foreign substances called antigens. Antibodies help the immune system to recognize and destroy these antigens. There are five major classes of antibodies, also known as immunoglobulins (Ig), which differ in their structure and function. The largest proportion of total antibodies present in the body is IgG.

IgG Antibodies:
IgG antibodies are the most abundant class of antibodies, accounting for approximately 75-80% of all antibodies in the body. They are produced in response to a variety of antigens, including bacteria, viruses, and other microorganisms. IgG antibodies are important in fighting infections and are able to cross the placenta, providing passive immunity to the fetus. They also play a role in the clearance of toxins and other harmful substances from the body.

Other Antibodies:
The other classes of antibodies are IgA, IgM, IgE, and IgD. IgA antibodies are found in mucosal secretions, such as saliva, tears, and breast milk, and play a role in preventing infections at mucosal surfaces. IgM antibodies are the first antibodies produced in response to an infection and are important in the early stages of the immune response. IgE antibodies are involved in allergic reactions and the defense against parasitic infections. Finally, IgD antibodies are found on the surface of B cells and have an unclear role in the immune response.

Conclusion:
In conclusion, IgG antibodies constitute the largest proportion of the total antibodies present in the body. They are important in fighting infections, clearing toxins, and providing passive immunity to the fetus. The other classes of antibodies also play important roles in the immune response, but IgG antibodies are the most abundant and versatile.