International Board of Certified Lactation Consultant (IBCLC) Practice Exam

Which immunoglobulin is predominantly found in human milk?

1. IgG

2. IgM

3. Secretory IgA

4. IgE

The correct answer is: Secretory IgA

The predominant immunoglobulin found in human milk is secretory IgA. This form of immunoglobulin plays a crucial role in the immune protection of infants, particularly in their gastrointestinal tract. Secretory IgA acts as a first line of defense against pathogens, preventing them from adhering to and penetrating the mucosal surfaces. It is especially important for breastfed infants, as it helps to shield them from infections during a critical period of immune development. While other types of immunoglobulins such as IgG, IgM, and IgE are present in the immune response, they do not have the same primary role in breast milk. IgG is the most abundant immunoglobulin in serum but is found in lower concentrations in human milk. IgM is primarily involved in the initial stages of immune responses and is also less prevalent in milk compared to secretory IgA. IgE is associated with allergic reactions and defense against parasitic infections, but it is not notably present in human milk. Overall, secretory IgA's unique structure and function make it essential for the immunological support of breastfeeding infants, underscoring its importance in human milk.