Breast milk contains antibodies that can fight infection. Those antibodies are present in high amounts in colostrum, the first milk that comes out of the breasts after birth.

However, there are antibodies in breastmilk the entire time a mother continues to nurse. Through these antibodies, the mother can pass on some protection from infectious illness she had in the past, and those she gets while breastfeeding. Breast milk can literally give babies a head start in preventing and fighting infections.

Breast milk also is made up of other proteins, fats, sugars and even white blood cells that work to fight infection in many different ways. They are especially helpful in fighting gastrointestinal infections, since breast milk heads right to the stomach and intestine when your baby eats.

The different factors in breast milk work directly within the intestine before being absorbed and reaching the entire body. This also sets the stage for a protective and balanced immune system that helps recognize and fight infections and other diseases even after breastfeeding ends.

Other factors in breast milk directly stimulate and support the immune system. These include lactoferrin and interleukin-6, -8 and -10. These proteins help to balance the immune system inflammatory response, which is needed for immune function but can be damaging in excess.

Sources-healthline.com