[Specificity of human proteoglycan radioimmunoassay]

The human articular cartilaginous proteoglycans (PG) R.I.A. is highly specific. The PG used as the standard and the 125I labelled molecule appear to be pure. Under these conditions, all the potential interfering substances which have been tested show no cross reaction. For instance, the Ag-Ab equilibrium is not affected by adding human IgG, human albumin, hyaluronic acid, chondroitin sulfate, rat type II collagen or total human serum proteins. This R.I.A. also exhibits a species specificity since there is no cross reaction with rat PG and negligible cross reaction with dog PG. The results obtained after addition of enzymes to the antigen demonstrate that the antigenic sites are localized on the protein region and not on the glycosaminoglycan region of the molecule.