Breast milk IgG: 'it does a baby good'.

Maternal milk antibodies are garnering increasing interest. While IgA dominates the milk antibody literature, IgG is emerging as a critical source of protection for the hyporesponsive neonate against life-threatening infections and as an important factor in instructing developing immunity. In this forum article, we reframe milk IgG from a minor constituent to a central protagonist in vertically transmitted postnatal immunity.