Demonstration of an antibody against platelet-derived growth factor

An antibody was raised in a rabbit against platelet-derived growth factor (PDGF), purified from human platelets. It recognized specifically ¹²⁵I-labelled PDGF, as demonstrated by gel electrophoretic analysis of precipitated radioactivity. Addition of immunoglobulins from the immune serum to cell cultures together with PDGF inhibited the multiplication-stimulating activity of the growth factor. Further, multiplication-stimulating activity in crude platelet lysate was retained upon passage over a column of Sepharose-bound anti-PDGF; it was recovered after elution of the column with acid. A radioimmunoassay for PDGF was developed, permitting the determination of 5 ng PDGF/ml. Platelet factor 4 and β-thromboglobulin, both being proteins of the platelet α-granule, did not cross-react in the radioimmunoassay for PDGF. The radioimmunoassay was utilized to examine the immunological relationship between PDGF and some other growth factors. The anionic growth factors previously demonstrated in pletelets were found to be antigenically distinct from cationic PDGF. Similar results were obtained with epidermal growth factor (EGF) or fibroblast growth factor (FGF). In contrast, osteosarcomaderived growth factor, a PDGF-like growth factor previously known as a product of cultured human osteosarcoma cells, showed some cross-reactivity in the radioimmunoassay for PDGF. It was concluded that osteosarcoma-derived growth factor (ODGF) has both physical-chemical and immunological properties in common with PDGF.