Synthesis of PDGF by cultured human T cells transformed with HTLV-I and II

Human T cells immortalized by human T lymphotropic virus (HTLV)-I and HTLV-II express the genes encoding both chains of platelet-derived growth factor (PDGF). These cells produce biologically active PDGF-like molecules of 31 and 32 kD, identified in the conditioned media of the virus-infected cells by direct immunoprecipitation, under non-reducing conditions, with antisera to PDGF. Upon reduction, the PDGF-like molecules are converted to mitogenically inactive single chains of 14 and 15 kD. The HTLV-transformed cells produce PDGF-like molecules regardless of their ability to produce viral particles. No PDGF-related mRNAs, PDGF-like proteins, nor PDGF-like mitogenic activity were detected in normal human T cells stimulated by phytohemagglutinin or in a T cell line which is not infected by HTLV. It is possible that one of the pathways of immortalization of T cells by HTLV-I or II might be by activation of PDGF-related genes.