Isolation of human monoclonal autoantibodies derived from pancreatic lymph node and peripheral blood B cells of islet autoantibody-positive patients

Abstract

Aims/hypothesis: Autoantibodies against pancreatic islets and infections by enteroviruses are associated with type 1 diabetes, but the specificity of immune responses within the type 1 diabetic pancreas is poorly characterised. We investigated whether pancreatic lymph nodes could provide a source of antigen-specific B cells for analysis of immune responses within the (pre)diabetic pancreas. Methods: Human IgG antibodies were cloned from single B lymphocytes sorted from pancreatic lymph node cells of three organ donors positive for islet autoantibodies, and from the peripheral blood of a patient with type 1 diabetes. Antibodies to insulinoma-associated antigen 2 (IA-2), GAD65, zinc transporter 8 (ZnT8) and Coxsackie B virus proteins were assayed by immunoprecipitation and by immunofluorescence on pancreatic sections. Results: Human IgG antibodies (863) were successfully cloned and produced from 4,092 single B cells from lymph nodes and peripheral blood. Reactivity to the protein tyrosine phosphatase domain of the IA-2 autoantigen was detected in two cloned antibodies: one derived from a pancreatic lymph node and one from peripheral blood. Epitopes for these two antibodies were similar to each other and to those for circulating antibodies in type 1 diabetes. The remaining 861 antibodies were negative for reactivity to IA-2, GAD65 or ZnT8 by both assays tested. Reactivity to a Coxsackie viral protein 2 was detected in one antibody derived from a peripheral blood B cell, but not from lymph nodes. Conclusions/interpretation: We show evidence for the infrequent presence of autoantigen-specific IgG+ B lymphocytes in the pancreatic-draining lymph nodes of islet autoantibody-positive individuals.