Human MFG glycoproteins have protective functions in the newborn that could be most important in preemies. We have therefore quantitated three glycoproteins of the human MFG, milk mucin, butyrophilin, and lactadherin(formally BA46), in 105 gastric aspirates of 21 human milk-fed and 12 formula-fed preterm infants (24-30 weeks), collected after 2 hours of fasting. Mucin and lactadherin were found in almost all gastric aspirates (57/57 and 40/57, respectively) in the milk-fed infants, in contrast to butyrophilin(6/57). The levels correlated positively with the degree of milk feeding and with the levels in the milk of the infants' mothers. Early milks (< 15 days) contained significantly more mucin (913 ± 142 μg/ml) and lactadherin (139 ± 19 μg/ml) than later milks (15-90 days) (mucin, 555 ± 51 μg/ml; lactadherin, 66 ± 5 μg/ml), while butyrophilin did not correlate with postnatal age. Mucin and lactadherin were detected in the gastric aspirates with pHs ranging from 1-7, while butyrophilin was found only in aspirates with pH > 4. No lactadherin or butyrophilin were detected in the gastric aspirates of formula-fed infants or of infants with no oral feeding. The mucin assay detected low levels of crossreacting material, probably a gastric MUC1 mucin, in the latter two control groups: 9.1 ± 1.6 μg/ml (1-24) and 48 ± 14 μg/ml(9-159), respectively. We conclude that mucin (which binds to S-fimbriatedE. coli) and lactadherin (which inhibits rotavirus replication) survive in the stomach and can protect preemies against invasive microorganisms. Supported in part by NIH grant No. HD30444 and CA39932.Table

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