Ingested soluble CD14 from milk is transferred intact into the blood of newborn rats

BACKGROUND: Milk contains immunological constituents that comprise an edible immune system conveyed from mother to newborn. Soluble Cluster of Differentiation 14 (sCD14) is a protein found in significant quantities in human milk (~8–29 μg/ml). At a tenfold lower concentration in the blood (~3 μg/ml), the most notable role of sCD14 is to sequester lipopolysaccharide of Gram-negative bacteria from immune cells. METHODS: To explore the pharmacodynamics of this milk protein and its biological fate, the biodistribution of radiolabeled sCD14 ((14)C, (125)I) was monitored in 10 d old rat pups. RESULTS: Up to 3.4 ± 2.2% of the radiolabeled-sCD14 administered was observed, intact, in the pup blood for up to 8 h post-ingestion. Additionally, 30.3 ± 13.0% of the radiolabeled-sCD14 administered was observed degraded in the stomach at 8 h post-ingestion. A reservoir of intact, administered sCD14 (3.2 ± 0.3%), however, remained in the stomach at 8 h post-ingestion. Intact sCD14 was observed in the small intestine at 5.5 ± 1.6% of the dose fed at 8h post-ingestion. CONCLUSIONS: The presence of intact sCD14 in the blood and gastrointestinal tract of newborns post-ingestion has implications in the development of allergies, obesity and other inflammation-related pathogeneses later in life.