Early Autoantibody Responses in Prediabetes Are IgG1 Dominated and Suggest Antigen-Specific Regulation

Abstract

The islet autoimmunity of preclinical type 1 diabetes remains poorly characterized in humans. In this paper, the IgG subclass response to the islet autoantigens insulin, glutamic acid decarboxylase, and IA-2 was studied sequentially from birth to diabetes onset or current follow-up in 26 autoantibody positive offspring of parents with diabetes. Islet autoantibody appearance was characterized by an early IgG1 peak response to one or more Ags, most commonly to insulin, at a median age of 2.2 yr (interquartile range, 2–2.9 yr). In five offspring, an acute fulminant β-cell destruction and diabetes onset occurred during this initial Ab response. In the remainder, early Ab levels declined markedly, and Ab peaks against other β cell Ags arose sequentially over several years suggesting regulation and spreading of autoimmunity. Second peak Ab responses to the same Ag were observed in only two offspring, both developing diabetes at this time. Two others developed diabetes with declining Ab levels. Abs of IgG1 subclass dominated against each Ag, and other subclasses, were usually only detected during peak IgG1 responses. The IgG4 response to insulin was exceptional, being dominant over IgG1 in four offspring and in five others appeared and/or persisted after IgG1 levels declined. These Th2-associated IgG4 responses were not correlated with protection from diabetes. The presence of IgG1-restricted responses to DA2 were associated with diabetes development. These findings suggest that type 1 diabetes has an early acute destructive phase of β cell autoimmunity, which may be regulated and which spreads chronically until diabetes onset.

Intralymphatic glutamic acid decarboxylase administration in type 1 diabetes patients induced a distinctive early immune response in patients with DR3DQ2 haplotype

“…GADA IgG 1, 2, 3, and 4 subclasses were measured by radio-binding assays using IgG subclass-specific biotin-labelled mouse-anti-human monoclonal antibodies bound on Streptavidin Sepharose High Performance beads (GE Healthcare Life Sciences, Freiburg, Germany) ( 17 ). Results were expressed as cpm and converted to arbitrary units (AUs) proportional to the cpm of a local standard serum.…”

Tissue Transglutaminase Immunoglobulin Isotypes in Children With Untreated and Treated Celiac Disease

“…The IgG‐tTG assay used in the present study constituted of the IgG1, IgG2, and IgG4 subclasses. Since it was recently shown that autoantibodies against glutamic acid decarboxylase (GAD65Ab) in type 1 diabetic patients before clinical onset are of the IgG1 subclass (13), we further tested if a specific subgroup of patients with IgG1‐tTG could be identified. The results showed a high prevalence (51%) of untreated CD patients considered positive for IgG1‐tTG.…”

“…IgG1‐tTG and IgM‐tTG were analyzed similarly except that protein A sepharose was replaced by biotin‐conjugated mouse anti‐human monoclonal IgG1 or IgM (BD Pharmingen, San Diego, CA) bound to streptavidin agarose (Pierce, Rockford, IL). A suspension of 20% streptavidin agarose and 3 μg biotinylated antibody per well in the assay reaction was prepared (13). Serum diluted 1/25 was incubated with 15,000 cpm of labeled tTG overnight at 4°C.…”

Autoantibodies to truncated GAD(96-585) antigen stratify risk of early insulin requirement in adult-onset diabetes

“…Approaches that improve specificity of GADA testing for identifying patients with type 1 diabetes would allow targeting of intensive monitoring, advice, and early insulin initiation to those most likely to benefit. Developments in assay technology allow measurement of additional characteristics beyond full-length (f-)GADA titre, including epitope specificity, affinity, and IgG subclasses (7)(8)(9). The clinical utility of these GADA characteristics is unclear.…”

“…Developments in assay technology allow measurement of additional characteristics beyond full-length (f-)GADA titre, including epitope specificity, affinity, and IgG subclasses (7-9). The clinical utility of these GADA characteristics is unclear.…”