RESUMEN
The aim of the present work has been to screen siblings of children with type 1 diabetes for some immunological markers of the disease, namely GAD, IA-2 and insulin autoantibodies and to study their possible relation with other risk factors. Siblings of 151 child with type 1 diabetes [287 healthy siblings] besides 100 healthy control subjects matched for age and sex. Subjects were subjected to estimation of GAD antibodies using radiolig and binding assay developed by Peterson et al, in 1994, IA-2 antibodies by radiolig and assay and insulin autoantibodies [IAA] using ELISA technique. Subjects with positive immunological markers were screened for HLA-DR3 and DR4 and first phase insulin release [FPIR] arter IV glucose infusion. revealed that 39.7% of healthy siblings were positive for one or more autoantibodies, 22.8% for 2 antibodies and 4.38% for 3 antibodies. GAD antibodies were present in 27.9%, IA-2 antibodies in 9% and IAA in 15.3% of healthy siblings. These prevalences were statistically significantly higher than those found in control subjects: 7%, 2%, 1.5% respectively No relation could be elicited between positivity of immunological markers in siblings and their age, sex, duration of breast feeding, age at cow's milk feeding nor with parents consanguinity. On the other h and, HLA-DR3, HLA-DR4 and DR3/DR4 were found in 29.4%, 64.7% and 88.2% respectively in seropositive subjects while in 27.5% 32.5% and 45% in seronegative healthy siblings. Conclusion the high prevalence of positivity of autoantibodies among siblings of type 1 diabetic children suggests the importance of an environmental factor, perhaps via a mechanism of antigenic mimicry. Also the results in relation to other risk factors may help to a better underst and ing of the immuno-genetic susceptibility and /or pathogenesis of type 1 diabetes in a particular population