Role of a single haemopoietic growth factor in multiple proliferative disorders of haemopoietic and related cells.

Activated T cells secrete a glycoprotein (P-cell-stimulating factor; PSF) that stimulates the proliferation of many types of haemopoietic progenitor cells and the pluripotential haemopoietic stem cells. Based on experiments in mice, it is proposed that some proliferative disorders of the pluripotential haemopoietic stem cell or its progeny may result from the abnormal production and secretion of PSF by these cells themselves. The secreted PSF binding to specific receptors on the surface of these cells causes autostimulation and uncontrolled proliferation. Acute non-lymphocytic leukaemias and the late stages of Hodgkin's disease might be due to such autostimulation. More chronic proliferative diseases (eg, chronic myeloid leukaemia and the early stages of Hodgkin's disease) may involve the expansion of an abnormal, immortalised, clone of pluripotential haemopoietic stem cells or committed haemopoietic progenitor cells that are not autonomous but remain strictly dependent for their proliferation and survival on the presence of exogenous PSF.