title: Simultaneous inhibition of insulin and somatomedin-C binding to cultured IM-9 lymphocytes by naturally occurring antireceptor antibodies.
abstract: A 53-y4-old male patient with insulin-resistant diabetes was found to have circulating inhibitors of both insulin and somatomedin-C binding. Serum obtained from the patient at the time of initial presentation inhibited 50% of both 125I-insulin and 125I-SM-C binding to IM-9 lymphocytes at dilutions of 1:150. Spontaneous improvement in the patient's diabetic state was associated with a simultaneous and equal decrease in the serum inhibitory titers for both radioligands. Scatchard analysis indicated that the observed serum-induced decrease in both insulin and SM-C binding was due to decreased receptor affinity, with no alteration in receptor number. The serum inhibitors of both insulin and SM-C binding were precipitated equally by Staph-A and also by 40% ammonium sulfate, suggesting they were immunoglobulins. The observation of naturally occurring autoantibodies against both the insulin and SM-C receptors suggests a structural homology between the two receptors.
mesh_terms: D000906:Antibodies; D003920:Diabetes Mellitus / Q000097:blood*; D006801:Humans; D007136:Immunoglobulins; D007328:Insulin / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I; D007700:Kinetics; D008214:Lymphocytes / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D011972:Receptor, Insulin / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D017451:Receptors, Somatomedin; D013002:Somatomedins / Q000378:metabolism*
chemical_list: D000906:Antibodies; D007136:Immunoglobulins; D007328:Insulin; D011956:Receptors, Cell Surface; D017451:Receptors, Somatomedin; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D011972:Receptor, Insulin