IgG AND IgA SERUM ANTIBODIES TO COW MILK IN BREASTFED OR FORMULA FED HEALTHY INFANTS

Cow milk proteins belong to major food antigens in infancy. The aim of the study was to determine the levels of cow milk-specific IgG and IgA antibodies in healthy infants, both breastfed and formula fed, during the first six months of age. The initial levels of these antibodies were determined by ELISA in the cord blood samples of 75 healthy infants. Their concentrations were then determined during a follow-up study in the same cohort both at 3 and at 6 months of age (37 a 17 samples). IgG antibodies to milk were high at birth and decreased significantly from birth to 3 months and further from 3 to 6 months in breastfed infants. In formula fed infants, however, the levels increased during the first trimester and insignificantly decreased at 6 months. The milkspecific IgA antibodies, low in cord blood serum, increased continually from birth to 3 and then to 6 months regardless of milk feeding. The increase, however, was higher in formula fed infants. It is concluded that cow milk-specific IgG production is stimulated after cow milk formula feeding but not during exclusive breastfeeding. The production of specific IgA, however, is stimulated even during exclusive breastfeeding. These findings may be due to different mechanisms of immune response after lowor high-dose antigen exposure.