Pregnancy induces nonimmunoglobulin insulin-binding activity in both maternal and cord blood serum

Abstract

SUMMARYTo evaluate whether pregnancy has any effect on insulin antibody levels and to test the concordance between a conventional radioimmunoassay and a new microassay for the detection of insulin antibodies, insulin antibodies were analysed in 104 mothers in early pregnancy and at delivery and in their newborn infants. Thirty-eight of the mothers had type 1 diabetes. The concordance between the assays was high in the samples taken in early pregnancy (95%), but substantially lower in the samples taken at delivery (40%) and in the cord blood samples (68%). A considerable proportion of the mothers at delivery, especially the unaffected mothers (71%), and the newborn infants of the unaffected mothers (32%) were positive for insulin antibodies in the conventional assay but not in the microassay. Insulin antibody levels increased in the mothers, significantly so in the unaffected mothers (P , 0´001), during pregnancy in the conventional assay, whereas in the microassay they decreased significantly (P , 0´01) in affected mothers and remained negative in the unaffected mothers. Since immune complexes are precipitated with protein A specific for IgG in the microassay and with polyethylene glycol lacking specificity for immunoglobulins in the conventional assay, our data indicate that insulin antibody levels decrease on average during pregnancy and that the increasing non-IgG anti-insulin activity observed in the conventional assay is induced by pregnancy and is present in both the maternal and the foetal circulation.

Age at introduction of new foods and advanced beta cell autoimmunity in young children with HLA-conferred susceptibility to type 1 diabetes

“…The disease sensitivity of the ICA assay in our laboratory was 100% and the specificity 98% in the most relevant standardisation workshop round [12]. Serum IAA were quantified with a microassay [13,14] and GADA and IA-2A with specific radiobinding assays [15,16] . Among these, 32 had been repeatedly positive for ICA plus at least one other autoantibody.…”

Fatty acid status in infancy is associated with the risk of type 1 diabetes-associated autoimmunity

“…IAA were quantified by microassay [29,30] and GADA and IA-2A were analysed using specific radiobinding assays [31][32][33]. Details of the autoantibody methods are described by Kimpimäki et al [34].…”

Characterization of the humoral immune response to islet antigen 2 in children with newly diagnosed type 1 diabetes.

“…All samples initially tested as having IA-2A levels above 90 RU were diluted in NHS to obtain reliable results from the linear part of the standard curve. IAA and GADAwere analyzed with specific radiobinding assays (14,15) with disease sensitivities of 44 and 82% and specificities of 98 and 97% respectively according to DASP 2005. ICA were quantified by a standard indirect immunofluorescence method (16).…”