Diabetes, Vol 49, Issue 10 1657-1665, Copyright © 2000 by American Diabetes Association
Effect of cow's milk exposure and maternal type 1 diabetes on cellular and humoral immunization to dietary insulin in infants at genetic risk for type 1 diabetes. Finnish Trial to Reduce IDDM in the Genetically at Risk Study Group
J Paronen, M Knip, E Savilahti, SM Virtanen, J Ilonen, HK Akerblom and O Vaarala
Hospital for Children and Adolescents, University of Helsinki, Finland. johanna.paronen@hus.fi
Type 1 diabetes is considered to be a T-cell-mediated autoimmune disease in
which insulin-producing beta-cells are destroyed. Immunity to insulin has
been suggested to be one of the primary autoimmune mechanisms leading to
islet cell destruction. We have previously shown that the first
immunization to insulin occurs by exposure to bovine insulin (BI) in cow's
milk (CM) formula. In this study, we analyzed the development of
insulin-specific T-cell responses by proliferation test, emergence of
insulin-binding antibodies by enzyme immunoassay, and insulin
autoantibodies by radioimmunoassay in relation to CM exposure and family
history of type 1 diabetes in infants with a first-degree relative with
type 1 diabetes and increased genetic risk for the disease. The infants
were randomized to receive either an adapted CM-based formula or a
hydrolyzed casein (HC)-based formula after breast-feeding for the first 6-8
months of life. At the age of 3 months, both cellular and humoral responses
to BI were higher in infants exposed to CM formula than in infants fully
breast-fed (P = 0.015 and P = 0.007). IgG antibodies to BI were higher in
infants who received CM formula than in infants who received HC formula at
3 months of age (P = 0.01), but no difference in T-cell responses was seen
between the groups. T-cell responses to BI at 9 months of age (P = 0.05)
and to human insulin at 12 (P = 0.014) and 24 months of age (P = 0.009) as
well as IgG antibodies to BI at 24 months of age (P = 0.05) were lower in
children with a diabetic mother than in children with a diabetic father or
a sibling, suggesting possible tolerization to insulin by maternal insulin
therapy. The priming of insulin-specific humoral and T-cell immunity occurs
in early infancy by dietary insulin, and this phenomenon is influenced by
maternal type 1 diabetes.