Which immunoglobulin is predominantly found in mucosal secretions and breast milk?

Which immunoglobulin is predominantly found in mucosal secretions and breast milk?

• A. IgA
• B. IgG
• C. IgM
• D. IgE

Answer: (A)

Secretory IgA is the antibody most abundant in mucosal secretions and breast milk. It is produced as a dimer by plasma cells in mucosa-associated lymphoid tissue and is transported across epithelial cells by the polymeric immunoglobulin receptor. As it passes into secretions, it acquires a secretory component that shields it from proteolysis, making it well suited to function in the harsh mucosal environment. In mucosal surfaces, secretory IgA neutralizes pathogens and toxins, prevents adherence to epithelial cells, and helps trap microbes in mucus. In breast milk, secretory IgA provides passive protection to the newborn by coating the infant’s gut and blocking pathogen colonization. Other antibodies like IgG, IgM, and IgE have important roles in other contexts, but they are not the primary immunoglobulin in mucosal secretions and breast milk, which is dominated by secretory IgA.

Secretory IgA is the antibody most abundant in mucosal secretions and breast milk. It is produced as a dimer by plasma cells in mucosa-associated lymphoid tissue and is transported across epithelial cells by the polymeric immunoglobulin receptor. As it passes into secretions, it acquires a secretory component that shields it from proteolysis, making it well suited to function in the harsh mucosal environment. In mucosal surfaces, secretory IgA neutralizes pathogens and toxins, prevents adherence to epithelial cells, and helps trap microbes in mucus. In breast milk, secretory IgA provides passive protection to the newborn by coating the infant’s gut and blocking pathogen colonization. Other antibodies like IgG, IgM, and IgE have important roles in other contexts, but they are not the primary immunoglobulin in mucosal secretions and breast milk, which is dominated by secretory IgA.