Potential ligands for cell adhesion molecules in human milk

Area of Science:

• Biochemistry
• Immunology
• Pediatrics

Background:

• Human milk contains complex carbohydrates crucial for infant development and immunity.
• Lewis antigens are important glycans found in various biological fluids, including milk.

Purpose of the Study:

• To isolate and characterize specific Lewis antigens (sialyl Lewis a, sialyl Lewis x, Lewis x, Lewis y) in human milk.
• To determine the forms in which these carbohydrate epitopes exist in milk: as free oligosaccharides or bound to proteins.

Main Methods:

• Ultracentrifugation and fast-protein liquid chromatography (FPLC) for isolation.
• Monoclonal antibodies, lectins, and Western blotting for epitope identification on whey proteins.
• High-performance thin-layer chromatography (HPTLC) and high-pH anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) for oligosaccharide characterization.

Main Results:

• Isolated glycoproteins and oligosaccharides bearing sialyl Lewis a, sialyl Lewis x, Lewis x, and Lewis y epitopes from human milk.
• Confirmed the presence of these epitopes on whey proteins and as lactose-derived oligosaccharides (< 10 kD).
• Identified these carbohydrate structures in the soluble fraction of milk, not of cellular origin, and also bound to high molecular weight proteins (> 100 kD).

Conclusions:

• Lewis antigens are present in human milk as both free oligosaccharides and glycoproteins.
• These milk-borne Lewis antigens may function as non-immunological protective factors for infants.
• Lewis antigens could play a role in modulating inflammatory processes in breastfed infants.