Description of a human placental anti-insulin receptor polyclonal antibody that activates insulin binding to the receptor in vitro.

A polyclonal anti-human placental insulin receptor antibody has been developed, and its interaction with the receptor has been studied in vitro. This antibody enhances insulin binding to the receptor, both in the immunoprecipitate and also in in vitro binding assay. In the Scatchard analysis of the insulin-receptor interaction, in the presence of the antiserum, a marked increase in Bmax is observed, while Kd remains more or less unaffected. This antibody recognizes insulin receptor from all tissues of old world monkey but does not recognize new world monkey, rat or mouse receptor. Insulin receptor binds to this antibody very strongly on a immunoaffinity column and cannot be eluted by gentle means, but it retains insulin stimulated tyrosine kinase activity while immobilized to immunoaffinity column. This antibody also activates insulin receptor mediated histone phosphorylation in vitro. It has been proposed that this antireceptor antibody modulates receptor function by causing conformational perturbation in vitro.