Serum antibodies to the major proteins found in cow's milk of Iranian patients with Type 1 diabetes mellitus.

The purpose of this study was to assess the humoral immune response to cow's milk proteins in Iranian children with Type 1 diabetes mellitus (T1DM). Eighty children aged 4-17 yr with T1DM from two centres in Iran (the Iranian Association of Diabetes in Tehran and Center for Diabetes Research in Hamedan), 37 apparently healthy siblings of diabetic patients (related controls), 82 apparently healthy age- and sex- matched controls (unrelated controls), and 32 patients aged 11-15 yr with auto-immune thyroiditis were examined for specific whole antibodies (Igs), IgG, and IgM to the major proteins found in cow's milk or to ovo-albumin by enzyme-linked immunosorbent assay (ELISA). A crude extract was made from 2.5% fat pasteurized cow's milk. This extract, together with individual commercial major proteins of cow's milk, was then used as antigen to evaluate the humoral immune response of the subjects to the individual proteins found in cow's milk or to cow's milk as a whole. A questionnaire on medical history, duration of exclusive and non-exclusive breast-feeding and daily intake of dairy products was completed before blood sampling. Diabetic children had significantly higher serum levels of Igs, IgG and IgM to the proteins found in cow's milk than unrelated healthy controls (p<0.001). Healthy siblings of diabetic patients, compared to unrelated controls, had significantly higher levels of serum Igs and IgG to cow's milk proteins (p<0.05 and p<0.01, respectively). Serum levels of Igs and IgG to the cow's milk proteins showed a significantly negative correlation with duration of non-exclusive breast-feeding but positive correlation with daily intake of dairy products. These correlations were stronger when calculated just within the T1DM group. In this group, serum levels of IgM to cow's milk proteins also showed a positive correlation with daily intake of dairy products. Though serum levels of IgG to casein were insignificantly higher in diabetic children than in healthy controls, there was a significant negative correlation between serum levels of IgG to casein and duration of non-exclusive breast-feeding. Again in the T1DM group, this correlation was stronger. There was no significant difference in serum levels of Igs, IgG or IgM to other major proteins of cow's milk or to ovo-albumin between groups. It was concluded that though high levels of Igs or IgG were found to cow's milk proteins, especially casein, it seems unrelated to the early introduction of cow's milk into an infant diet and the onset of T1DM in Iranian subjects.