Which specific antibody is primarily found in breast milk and secretions?

The correct answer is C, as Immunoglobulin A (IgA) is the specific antibody that is primarily found in breast milk and various secretions such as saliva, tears, and mucous. IgA plays a crucial role in the immune defense of mucosal surfaces. It acts as a first line of defense by preventing pathogens from adhering to and penetrating epithelial cells, which is particularly important in infants who rely on breast milk for their initial immune protection.

In the context of breastfeeding, IgA can protect infants from infections by neutralizing pathogens and limiting their access to the infant's immune system. This is especially vital in the early months of life when an infant's immune system is still maturing.

Other types of antibodies, while important in various roles within the immune system, are not primarily associated with breast milk. IgG is the most abundant antibody in the bloodstream and is vital for systemic immunity but does not play a significant role in secretions. IgM is primarily involved in the initial response to an infection and is typically found in the bloodstream, while IgE is related to allergic reactions and responses to parasitic infections. Therefore, IgA is uniquely positioned as the key antibody present in breast milk and secretions.