Antibody production system modulated by oral administration of human milk and TGF-beta.

Human milk contains large amounts of transforming growth factor-beta (TGF-beta), which exerts powerful suppressive effects on many immune functions. Oral administration of human milk and TGF-beta in mice strongly inhibited anti-sheep red blood cell (SRBC) responses obtained following oral immunization with SRBC, but enhanced the responses elicited by intraperitoneal, intrabronchial or intravenous immunization with SRBC. Anti-SRBC antibody responses stimulated by intraperitoneal or intravenous immunization with SRBC failed to augment when TGF-beta-depleted human milk was given orally. These findings suggest that TGF-beta in human milk functions as an adjuvant for protective antibody responses against parenteral infections.