Step 1: Understanding the Question:
Colostrum is the yellowish fluid produced by mothers in the first few days after birth. The question asks for the predominant immunoglobulin (antibody) providing immunity to the infant via this milk.
Step 2: Detailed Explanation:
Human colostrum is rich in nutrients and antibodies that provide passive immunity to the newborn.
The most prevalent antibody in secretions like colostrum, saliva, and tears is Immunoglobulin A (IgA).
Specifically, it exists as Secretory IgA, which is resistant to degradation by digestive enzymes in the infant's gut.
It forms a protective layer on the mucosal surfaces of the infant's digestive and respiratory tracts, preventing pathogen attachment.
Step 3: Final Answer:
IgA is the most abundant antibody in colostrum.