Alpha-lactalbumin in human milk alters the proteolytic degradation of soluble CD14 by forming a complex

William J. Spencer, Andrew Binette, Tonya L. Ward, Laura D.R. Davis, David R. Blais, Joann Harrold, David R. MacK, Illimar Altosaar

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


Mother's milk represents a foundational step in the proper development of newborn immunity. This is achieved, in part, through the action of numerous regulatory proteins such as soluble cluster of differentiation 14 (sCD14) found in significant quantities in human milk (∼25-50 μg/mL). In adults, CD14 stimulates cytokine production in response to lipopolysaccharide (LPS), the major lipid component found in the outer membrane of Gram-negative bacteria. However, the fate and function of sCD14 in the neonatal gastrointestinal (GI) tract are unknown and may function differently from adults. Therefore, we administered human sCD14 to experimental animals and observed that it persisted in the upper GI tract after feeding. In our search for potential proteolytic protectants, immunoprecipitation of sCD14 from human milk revealed a 15-kD novel protein that copurified with sCD14. Mass spectrometry analysis of the protein identified alpha-lactalbumin. CD14 was also identified by immunoblot after immunoprecipitation of alpha-lactalbumin from milk. In vitro digestion assays revealed that purified alpha-lactalbumin decreases the proteolytic degradation of human milk derived sCD14 in vitro, suggesting a mechanism by which this key LPS receptor may remain functional in the neonate gut.

Original languageEnglish (US)
Pages (from-to)490-493
Number of pages4
JournalPediatric Research
Issue number6
StatePublished - Dec 2010


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