Review article: Protection against infections has been well evidenced during lactation against, e.g., acute and prolonged diarrhea, respiratory tract infections, otitis media, urinary tract infection, neonatal septicemia, and necrotizing enterocolitis. There is also interesting evidence for an enhanced protection remaining for years after lactation against diarrhea, respiratory tract infections, otitis media, Haemophilus influenzae type b infections, and wheezing illness. In several instances the protection seems to improve with the duration of breastfeeding.
A few factors in milk like anti-antibodies (anti-idiotypic antibodies) and T and B lymphocytes have in some experimental models been able to transfer priming of the breastfed offspring. This together with transfer of numerous cytokines and growth factors via milk may add to an active stimulation of the infant's immune system. Such an enhanced function could also explain why breastfeeding may protect against immunologic diseases like celiac disease and possibly allergy. Suggestions of protection against autoimmune diseases and tumors have also been published. Hanson LA. "Breastfeeding provides passive and likely long-lasting active immunity. Ann Allergy Asthma Immunol 1998 Dec;81(6):523-33; quiz 533-4, 537