Abstract
Diabetic retinopathy (DR) induces the breakdown of the blood-retinal barrier and promotes neuroinflammation, although autoimmune responses to sequestered retinal antigens remain poorly understood. In this study, we investigated the autoantibodies for retinal antigens in sera from diabetic macular edema (DME) patients. Screening by immunoblotting demonstrated that IgG from 7 of 10 DME sera samples reacted to an ~102-kDa autoantigen from porcine retinas. Immunoprecipitation with autoantibodies from DME sera and subsequent mass spectrometry enabled us to identify hexokinase 1 as an autoantigen reactive to IgG from DME sera. IgG in 7 of 10 DME sera partially colocalized to hexokinase 1 in the outer plexiform layer of rodent retinas. Quantitative analyses using enzyme-linked immunosorbent assays revealed that the serum titers of this autoantibody were significantly higher in the DME sera than those in the sera from diabetic patients without DME, and 20 (24.1%) of the 83 DME serum samples had higher IgG titers than the cutoff value (mean + 2 standard deviations of the sera from diabetic patients without DR). Multivariate logistic regression analysis confirmed that the higher titer of anti-hexokinase 1 IgG was clinically feasible for the diagnosis of DME. These data identify anti-hexokinase 1 antibody as a serum biomarker of a subset of DME.
Highlights
Patients with diabetes mellitus (DM) routinely undergo blood sampling in the internal medicine clinic
Additional immunofluorescence analysis using patients’ sera as primary antibodies revealed that 7 (70.0%) of the 10 diabetic macular edema (DME) sera exhibited immunoreactivity to autoantigens in the outer plexiform layer (OPL) of C57BL/6 J mice
We identified anti-hexokinase 1 antibody as a novel autoantibody in sera from a subgroup of DME patients
Summary
Patients with diabetes mellitus (DM) routinely undergo blood sampling in the internal medicine clinic. We identified anti-hexokinase 1 antibody as a novel serum autoantibody using a combination of biochemistry and mass spectrometry, and we investigated the association between the antibody titer and clinical parameters in DME. To identify the antigens reactive to the autoantibodies, we performed immunoprecipitation using DME sera and analyzed the precipitated proteins by subsequent mass spectrometry (Fig. 2a, Supplementary Table S1).
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