title: Dynamic pattern of disease-associated autoantibodies in siblings of children with type 1 diabetes: a population-based study.
abstract: To study the dynamics of disease-associated humoral immune responses, we analyzed autoantibodies to the IA-2 protein (IA-2A), glutamic acid decarboxylase (GADA), and insulin (IAA) and also islet cell antibodies (ICA) in a population-based, prospective, representative series of 710 siblings (<20 years of age) of children with type 1 diabetes. Positivity for single autoantibodies was observed in 8-13% of these siblings during an average follow-up of 4 years. The overall incidence rates per 1,000 years (number of cases/person-years in parentheses) for positive seroconversion of IA-2A were nine (19/2,123), followed by six (12/2,049) for GADA, 19 (40/2,111) for IAA, and 16 (31/1965) for ICA. Positive seroconversions seemed to be associated with a young age of the sibling, HLA DR3/DR4 heterozygosity, HLA identity, and a high initial number of detectable autoantibodies. The overall incidence rates per 1,000 years (number of cases/person-years in parentheses) for inverse seroconversion of IA-2A were 76 (12/157), followed by 42 (10/237) for GADA, 460 (32/70) for IAA, and 27 (9/331) for ICA. No consistent risk factor for inverse seroconversions was present, although seroconversions were most frequent in siblings with older age, male sex, HLA phenotypes other than DR3/DR4, a small family size, and no other autoantibodies detectable at seroconversion. Altogether, these observations indicate that beta-cell autoimmunity may be induced at any age in childhood and adolescence. HLA-conferred genetic disease susceptibility is a strong determinant of persistent beta-cell autoimmunity, but environmental factors may also contribute to such autoimmunity.
authors.affiliation: Pediatrics University of Oulu, Oulu, Finland. Kaisa.Savola@oulu.fi
authors.forename: K
authors.initials: K
authors.lastname: Savola
authors.forename: E
authors.initials: E
authors.lastname: Läärä
authors.forename: P
authors.initials: P
authors.lastname: Vähäsalo
authors.forename: P
authors.initials: P
authors.lastname: Kulmala
authors.forename: H K
authors.initials: HK
authors.lastname: Akerblom
authors.forename: M
authors.initials: M
authors.lastname: Knip
mesh_terms: D000293:Adolescent; D000328:Adult; D001323:Autoantibodies / Q000032:analysis*; D002648:Child; D002675:Child, Preschool; D003922:Diabetes Mellitus, Type 1 / Q000235:genetics* / Q000276:immunology*; D005260:Female; D005968:Glutamate Decarboxylase / Q000276:immunology; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007328:Insulin / Q000276:immunology; D007515:Islets of Langerhans / Q000276:immunology; D008297:Male; D011446:Prospective Studies
chemical_list: D001323:Autoantibodies; C096322:ICA512 autoantibody; D007328:Insulin; D005968:Glutamate Decarboxylase