Which immunoglobulin is present in the breast milk: September 2005

Ans. A: Ig A Secretory IgA is the principal immunoglobulin of breast milk/colostrum. It is synthesized in the mammary epithelial cell by the coupling of two IgA molecules, produced locally by lymphocytes resident in the breast tissue, with two proteins, J-chain and secretory component. The specificity of breast milk secretory IgA antibodies reflects the mother's exposure to mucosal infection and is independent of the specificity profile of blood-borne IgA.