Local and systemic immune responses to food antigens in neonates and infants.
Normal newborns regularly form circulating antibodies to milk proteins by 10 to 14 days of life. Concentrations of these antibodies are influenced by gestational age but not by passive maternal antibody. Secretory antibodies of the IgA and IgM-isotype directed against casein and beta-lactoglobulin are present in the saliva of normal neonates. SIgA-anti-casein is higher in saliva of newborns at risk to develop atopic disease.