E. Kawasaki et al., AUTOANTIBODIES TO PROTEIN-TYROSINE PHOSPHATASE-LIKE PROTEINS IN TYPE-I DIABETES - OVERLAPPING SPECIFICITIES TO PHOGRIN AND ICA512 IA-2/, Diabetes, 45(10), 1996, pp. 1344-1349
Citations number
20
Categorie Soggetti
Endocrynology & Metabolism","Medicine, General & Internal
An insulin granule membrane protein, protein (phosphatase homologue of
granules from rat insulinoma), with homology to islet cell antigen (I
CA) 512/IA-2 has recently been cloned from an insulinoma cDNA expressi
on library with antigranule membrane sera. We have developed a radioim
munoassay for detecting anti-phogrin autoantibodies using in vitro tra
nscribed and translated phogrin and have established the sensitivity a
nd specificity of this assay, Thirty-two of 57 (56%) new-onset patient
s with type I diabetes and 26 of 44 (59%) first-degree relatives follo
wed to diabetes had anti-phogrin antibody levels exceeding the 99th pe
rcentile of 108 normal control subjects. Levels of anti-phogrin autoan
tibodies correlated with ICA512/IA-2 autoantibodies (r = 0.82, P < 0.0
001), but minimally with insulin autoantibodies (r = 0.20, P = 0.05) a
nd not with GAD65 autoantibodies (r = 0.16, P = 0.12), Ninety-eight pe
rcent (57 of 58) of-patients positive for anti-phogrin autoantibodies
were also positive for autoantibodies against ICA512/IA-2. Nine percen
t (9 of 101) of new-onset patients and relatives followed to diabetes
mere ICA512/IA-2 autoantibody-positive but anti-phogrin autoantibody-n
egative. Preincubation of sera with recombinant ICA512/IA-2 protein co
mpletely for the majority and partially for a minority inhibited bindi
ng to in vitro translated phogrin. In three relatives in which ICA512/
IA-2 autoantibodies concerted to positivity with sequential follow-up,
anti-phogrin autoantibodies developed at the same time, These results
suggest that anti-phogrin and ICA512/IA-2 autoantibodies are related
subsets of anti-islet autoantibodies.