American Board of Surgery Qualifying Exam (ABS QE) Practice Test

What is the primary function of IgA?

1. Participate in allergic reactions

2. Provide mucosal immunity

3. Mainly present in blood circulation

4. Act as a primary antibody in acute infections

The correct answer is: Provide mucosal immunity

The primary function of Immunoglobulin A (IgA) is to provide mucosal immunity. This antibody is predominantly found in mucosal areas such as the gastrointestinal tract, respiratory tract, and urogenital tract, as well as in secretions such as saliva, tears, and breast milk. By being present in these locations, IgA plays a crucial role in the immune defense against pathogens that enter the body through mucosal surfaces. It works by preventing the adherence of pathogens to epithelial cells and neutralizing toxins before they can cause harm. IgA is particularly important in evaluating the immune status of individuals, especially in pediatric populations due to its role in providing passive immunity to infants through breast milk, enhancing their protection against infections in the early stages of life. Other options do not accurately reflect the primary role of IgA; for instance, while IgA may play a minor role in some allergic responses, it is not its primary function. Similarly, IgA is not mainly present in blood circulation, which is more characteristic of other immunoglobulin classes like IgG. Lastly, IgA is not the primary antibody involved in acute infections; that role is typically filled by IgM during the initial immune response.