Neonatal Nurse Practitioner Practice Exam 2025 – Complete Prep Resource

The immunoglobulin that is primarily secreted in breastmilk is Immunoglobulin A (IgA). This antibody plays a crucial role in mucosal immunity, which is particularly important for infants as their immune systems are still developing. IgA found in breastmilk helps to protect the newborn from infections by binding to pathogens and preventing them from adhering to mucosal surfaces, thereby reducing the likelihood of gastrointestinal and respiratory infections.

In contrast, Immunoglobulin G (IgG) is the predominant immunoglobulin found in blood and extracellular fluid and is involved in systemic immunity but is not secreted in significant amounts in breastmilk. Immunoglobulin M (IgM) is important in the early stages of infection and is primarily found in the blood, playing a limited role in breastmilk. Immunoglobulin E (IgE) is mainly associated with allergic responses and parasitic infections and is also not significantly present in breastmilk.

Thus, the presence of IgA in breastmilk serves a protective function for infants, making it the correct answer in this context.