HUMAN ALPHA-LACTALBUMIN AND BOVINE BETA-LACTOGLOBULIN ABSORPTION IN INFANTS

We investigated gut permeability to human alpha-lactalbumin (ALA) and bovine beta-lactoglobulin (BLG) in 20 infants from birth to 8 months o r until weaning, before which they were on a strictly cow's-milk-free diet. We measured the proteins with a sensitive, solid-phase, double-s andwich immunofluorometric assay. Median (range) levels of serum ALA o n days 3-4 after birth, and at 1 and 2 months of age were 31 (12-225), 6 (0-55), and 2 (0-16) mug/l serum per g ALA given per kg body weight , respectively. At 3, 5, and 8 months of age, only trace amounts of AL A were found. One week after weaning, serum BLG was found in 5/13 infa nts (38%) and at 2 weeks in 3/14 infants (21%), with median concentrat ions of 7 and 4 mug/l serum per g BLG given per kg body weight, respec tively. No ALA could be detected in any of these samples. In absorptio n of ALA, the four infants who had allergic symptoms did not differ fr om those without symptoms. Thus, systemic absorption of ALA and BLG do es occur in infants. Absorption of ALA is greatest after birth, when 3 x 10(-4) (median) of the given antigens are absorbed, but absorption decreases rapidly. The gut may often be transiently permeable to BLG w hen cow's-milk-based formula is started.