Disease-associated antibodies in offspring of mothers with IDDM.

We studied 20 infants of mothers with IDDM participating in a pilot study for a dietary intervention trial, testing the hypothesis that avoidance of cow's milk proteins early in life will reduce the risk of subsequent IDDM. The aim was to evaluate the elimination of IDDM-associated antibodies from the peripheral circulation of the infants, the possible emergence of autoantibodies indicating beta-cell destruction, and the influence of the dietary intervention and genetic disease susceptibility on the development of these autoantibodies. Transplacentally transferred islet cell antibodies (ICAs) and antibodies to the 65-kDa isoform of glutamic acid decarboxylase (GAD65As) disappeared from the peripheral circulation of most infants over the first few months of life and in all infants before the age of 9 months. Insulin antibodies were eliminated before the same age in all cases but one. The higher the initial antibody level was, the longer the time required for elimination. Four infants tested positive for insulin autoantibodies (IAAs) on at least one occasion during the first year of life, and 5 out of 16 unaffected subjects (31%) had IAAs at the age of 2 years. One infant became positive for IAA before the age of 6 months, with increasing levels later, seroconverted to positivity for ICAs and GAD65As between 6 and 9 months and presented with clinical IDDM at the age of 14 months. He had the HLA DQB1*0302/x genotype, which predisposes carriers to IDDM, and had been given the casein hydrolysate formula as supplementary milk. There were no significant differences in the levels of various autoantibodies between two groups of subjects defined either on the type of dietary intervention or the degree of genetic susceptibility. The findings indicate that transplacentally transferred antibodies related to IDDM are usually eliminated from the peripheral circulation of infants before 9 months of age and that IDDM-associated autoantibodies may emerge before the age of 6 months. Our results also illustrate that avoidance of cow's milk proteins over the first 9 months of life does not provide total protection against IDDM.