Stocks of the WHO islet cell antibody, GAD65 antibody, and IA‐2 antibody standard (NIBSC 97/550) are now very limited. We have therefore made and tested a series of control preparations in which human monoclonal autoantibodies to IA‐2 and to GAD65 were diluted in antibody‐negative human serum to different concentrations. Three different diabetes autoantibody controls (DAC 1–3) were made as was a negative control preparation. Aliquots containing 1 mL of autoantibodies in serum were freeze‐dried. After reconstitution (with 1 mL of water) the controls were tested by 125I‐IA‐2 immunoprecipitation assay (IPA), 125I‐GAD65 IPA, GAD65 Ab ELISA and IA‐2 Ab ELISA (kits from RSR Ltd.) and for ICA by immunofluorescence test (IFT). DAC1 is particularly suitable as a control for the 125I IA‐2 IPA; DAC2 is suitable for the 125I‐GAD65 IPA, GAD65 Ab ELISA, and IA‐2 Ab ELISA; and DAC3 is suitable for the ICA IFT. Freeze‐dried preparations showed good stability at 37°C. Reconstituted liquid preparations were stable when stored at 4°C and at 37°C. Availability of an essentially unlimited supply of these reagents should be useful in establishing reproducible and comparable measurements of diabetes autoantibodies in different laboratories using different assays.
