Characterization of insulin autoantibodies in a patient with autoimmune hypoglycemia.
A 60-year-old man referred because of hypoglycemic bouts was found to have insulin autoantibodies. Total plasma insulin was as high as 1.44 nmol/l. Both plasma free insulin and C-peptide were in the normal range. The indirect immunofluorescence technique showed positivity for antinuclear antibodies. The T-lymphocyte populations in the peripheral blood were normal. When serum binding capacity for pork insulin was measured, antibodies binding pork insulin were not detected. The patient's serum bound 125I-insulin. The binding protein was identified to be an immunoglobulin G. The kinetics of dissociation, studied by the Scatchard analysis of the autoantibody, showed a curvilinear plot, which was analyzed in two components. Cold human insulin was able to compete with 125I-insulin for the antibody binding site (I.C.50 = 1.35 nmol/ml). These antibodies were apparently not associated with antibodies directed against the insulin receptor.
Di Cerbo
A
A
Divisione di Endocrinologia, IRCCS Casa Sollievo della Sofferenza, San Giovanni Rotondo, Foggia, Italy.
Tassi
V
V
Scillitani
A
A
Zoppetti
G
G
De Filippis
V
V
D001323:Autoantibodies / Q000276:immunology* / Q000378:metabolism*; D001327:Autoimmune Diseases / Q000150:complications / Q000276:immunology* / Q000378:metabolism; D001798:Blood Proteins / Q000378:metabolism; D002478:Cells, Cultured; D006801:Humans; D007003:Hypoglycemia / Q000150:complications / Q000276:immunology* / Q000378:metabolism; D007074:Immunoglobulin G / Q000096:biosynthesis / Q000378:metabolism; D007330:Insulin Antibodies / Q000276:immunology* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D011485:Protein Binding; D011972:Receptor, Insulin / Q000276:immunology
D001323:Autoantibodies; D001798:Blood Proteins; D007074:Immunoglobulin G; D007330:Insulin Antibodies; D011972:Receptor, Insulin