Reevaluation of Autoantibodies to Islet Cell Membrane in IDDM: Failure to Detect Islet Cell Surface Antibodies Using Human Islet Cells as Substrate

Abstract

Since their demonstration in 1975, ICSAs have been proposed as serological markers and pathogenic elements in IDDM. ICSAs are detected in the sera of most newly diagnosed IDDM patients by indirect IFL that uses viable preparations of rat islet or insulinoma cells as substrate, but they also can be detected by using human insulinoma or fetal islet cells. We have tried to demonstrate ICSAs in the sera of 31 newly diagnosed diabetic patients, including 6 positive samples on human fetal islet cells, which used their natural target for the first time: normal human islet cells. In spite of using different types of preparations of these cells (i.e., freshly dispersed cell suspensions, monolayer cultures, or dispersed islets after culture), ICSAs could not be detected by IFL under the UV microscope, nor by flow cytometry. In contrast, 9 of 29 of the sera gave a positive staining on the RIN rat insulinoma cells. In an attempt to establish whether the putative ICSA autoantigen is present in the surface of human islet cells in the diabetic pancreas, the insulitis microenvironment was emulated by exposing the islets to three types of stress: 1) cytokines (IFN-gamma and TNF-alpha); 2) heat shock; and 3) hyperglycemia. However, diabetic sera failed again to recognize membrane antigens on the islet cells after either of these treatments. Neither were islet cells from a newly diagnosed diabetic patient stained by its autologous serum (ICA titer > 80 JDF U). These results suggest that ICSA autoantigen is not expressed in the membrane of human islet cells and therefore raises doubts about their proposed pathogenic role.

Seroconversion to Multiple Islet Autoantibodies and Risk of Progression to Diabetes in Children

“…22 Moreover, none of the known islet autoantigens are expressed on the β-cell surface, and no direct effect of islet autoantibodies on β-cell function has been reproducibly observed. 23 However, a pathogenetic role of the autoantibodies cannot be excluded. The observation made in this study that multiple islet autoantibodies are associated with highest risk of type 1 diabetes, together with previous indications that risk is associated with the titer of some islet autoantibodies, is consistent with a role in pathogenesis.…”

Anti-CD38 autoantibodies: Characterisation in new-onset Type I diabetes and latent autoimmune diabetes of the adult (LADA) and comparison with other islet autoantibodies

“…The finding that anti-CD38 aAbs are not an ICA subfraction is not surprising if a key difference in the epitopes recognised is considered. Indeed, the ICA immunofluorescence is located in the cytoplasm [44], while CD38 is expressed on the cell surface; moreover, all the anti-CD38 aAbs selected so far recognize its extracellular portion, since the target rsCD38 used in our assay does not include the transmembrane and intracellular domains [34].…”

T-cell reactivity to glutamic acid decarboxylase in stiff-man syndrome and cerebellar ataxia associated with polyendocrine autoimmunity

“…The presence of GAD‐Abs was assessed by radioimmunoassay (RIA), as previously described [11] and islet cell antibodies (ICA), by standard immunofluosrescence methods [26]. Antibodies to IA‐2 (IA‐2 Abs) were measured by radioimmunoassay using 125 I‐labelled human recombinant tyrosine phosphatase [27] and a commercial kit (CIS Biointernational, Gif‐sur‐Yvette, France).…”