Before I move on from body parts - transmales please remember that men are mammals too.
A Breast feeding promotional site,
Did a search ,
mothers milk and immune system
Mother's Milk: A Purposeful Contribution to the Development of the Infant Microbiota and Immunity
Breastfeeding Contributes to Physiological Immune Programming in the Newborn
Breast Milk: Proactive Immunomodulation and Mucosal Protection Against Viruses and Other Pathogens