Tissue-specific antibodies against the fibroblast insulin receptor in a patient with lupus nephritis and hypoglycemia.
We recently reported that the serum from a patient with lupus nephritis, insulin resistance, and hypoglycemia contains multiple populations of antibodies directed at the human insulin receptor. In the present study, we found a subpopulation of antibodies (eluted from a protein A-Sepharose affinity column at pH 4.3) directed at the human fibroblast insulin receptor. When tested against human placental membranes, IM-9 lymphocytes, circulating monocytes and erythrocytes, and isolated adipocytes, the antibody subpopulation did not compete with 125I-insulin for binding to its receptor. In contrast, the antibody subpopulation competed with 125I-insulin for binding to the human fibroblast insulin receptor. This antibody subpopulation stimulated [3H]alpha-aminoisobutyric acid [( 3H]AIB) uptake to these cells. Unlike the effect of insulin, however, this regulation of transport was not antagonized by a mouse monoclonal antibody to the human insulin receptor that inhibits 125I-insulin binding. These studies indicate, therefore, that a tissue-specific antibody subpopulation can occur spontaneously in patients with antibodies to the human insulin receptor. Furthermore, they indicate the presence of anti-insulin receptor autoantibodies specifically directed against a tissue that is not primarily involved in glucose metabolism.
D000818:Animals; D000906:Antibodies / Q000276:immunology* / Q000302:isolation & purification; D000911:Antibodies, Monoclonal / Q000276:immunology; D001323:Autoantibodies / Q000276:immunology; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D005921:Glomerulonephritis / Q000378:metabolism*; D006801:Humans; D007003:Hypoglycemia / Q000378:metabolism*; D007074:Immunoglobulin G / Q000276:immunology / Q000302:isolation & purification; D007333:Insulin Resistance; D008180:Lupus Erythematosus, Systemic / Q000378:metabolism*; D008875:Middle Aged; D051381:Rats; D011919:Rats, Inbred Strains; D011972:Receptor, Insulin / Q000276:immunology* / Q000378:metabolism
D000906:Antibodies; D000911:Antibodies, Monoclonal; D001323:Autoantibodies; D007074:Immunoglobulin G; D011972:Receptor, Insulin