Haemopoietic growth factors and leukaemogenesis.

Haemopoietic stem cells give rise to all the different mature circulating blood cell types by a process of differentiation, proliferation and development. T h e pluripotent haemopoietic stem cells are required throughout the lifespan of an animal because mature cells, such as erythrocytes and neutrophils, are short lived. T h e defining characteristic of the stem cell population is therefore its continued pluripotentiality: it can both generate lineage-restricted progenitor cells which proliferate and develop into mature cells and self-renew to maintain the population of stem cells throughout the life of the organism. T h e structure and regulatory mechanisms that govern blood cell production have been the subject of intense research. It is hoped that, by