Final answer:
The antibody class secreted in breast milk that helps protect newborns is IgA, which is highly effective against pathogens and provides passive immunity through breastfeeding.
Step-by-step explanation:
The antibody class secreted in breast milk that helps protect the newborn through neutralization and agglutination of an antigen is IgA. This class of antibody is secreted by exocrine glands and is highly effective against digestive and respiratory pathogens. Furthermore, IgA is known to pass immunity to an infant through breastfeeding, playing a critical role in conferring passive immunity to the child during the first months of life.