TSH BINDING BY GLOBULINS FROM PATIENTS WITH GRAVES-DISEASE

Abstract

Forty-one globulin preparations from patients with Graves'' disease were tested for their specific TSH binding properties and compared with their thyroid stimulating immunoglobulin activity in human thyroid membrane competition assay, adenylate cyclase stimulation and colloid droplet formation. The preparations tested were divided into 2 well distinguishable groups according to their specific TSH binding: 24 of 41 samples contained thyrotropin binding sites similar to the globulins from normal healthy persons (A-type binding, Kd: 1.2 pmol/g and Bmax [maximum binding]: 0.8 pmol g-1) and 17 samples bound TSH with lower affinity but higher capacity (B-type binding, mean Kd: 15.3 pmol-1 g, mean Bmax: 2.7 pmol g-1). Both A- and B-type TSH binding globulins containing samples were active in binding to human thyroid membrane, in droplet formation and adenylate cyclase stimulation. There was a linear correlation between the potential TSH binding capacity of a B-type sample and the percentage adenylate cyclase stimulation and droplet formation; a reverse correlation was found with their thyroid membrane binding activity. B-type TSH binding globulins may play a role in the formation and/or modification of the pathogenetic TSH action.