OSMT (Ontario Society of Medical Technologists) Practice Exam

The most abundant classification of antibody in the human body is IgG. This type of antibody plays a crucial role in the immune response, as it is responsible for the majority of antibody-based immunity against invading pathogens. IgG makes up approximately 70-75% of all immunoglobulins found in serum, which is significantly higher than any other class of antibodies.

IgG is particularly effective in neutralizing toxins and viruses, as well as opsonizing bacteria, which enhances their destruction by phagocytes. Its ability to cross the placenta also provides passive immunity to the fetus, making it an essential antibody for protection in early life.

In contrast, IgM is primarily involved in the initial stages of the immune response. IgA is predominantly found in mucosal areas and secretions, such as saliva and breast milk, playing a crucial role in mucosal immunity. IgD's function is not as well understood but is believed to play a role in the activation of B cells. Therefore, IgG is the clear choice when considering the most abundant antibody classification in the immune system.