There are five types or class of antibodies found in the human body these are IgA, IgM, IgD, IgE, and IgG. Out of these five class IgA antibody is found in an abundant amount in the mother's milk or colostrum.
Infant take this antibody from the mother through breastfeeding which protects the infant from may pathogenic microbes. The immunity in which antibodies are taken from outside is called passive immunity.
Therefore the passive immunity source that is given by the mother to baby through breast milk is called IgA.
