Immune system effects of baby milk, illustration. Sequence showing how babies acquire immunity to diseases from their mother's milk. At top left, the mother is exposed to microbes (here, the bacteria E. coli). At top right, lymphocytes in the mother's intestines react to the presence of the E. coli. At centre left, the mother's immune response produces the antibody immunoglobulin (IgA), which migrates to the mother's breast (centre right). At lower left, the baby ingests milk from the mother's breast containing IgA. This results in the baby acquiring immunity to E. coli (lower right).