- Autoantibodies in IDDM primarily recognize the 65,000-M(r) rather than the 67,000-M(r) isoform of glutamic acid decarboxylase. Hagopian, W.A., Michelsen, B., Karlsen, A.E., Larsen, F., Moody, A., Grubin, C.E., Rowe, R., Petersen, J., McEvoy, R., Lernmark, A. Diabetes (1993)