Growth factors for haemopoietic cells

Erythropoietin is made in the kidney in response to the oxygencarrying capacity of the blood and is required at all stages in the growth and differentiation of red blood cells. 

Lymphokines are secreted into the culture medium by hy-bridomas ( 13.6) and may be isolated following growth of cells in bioreactors ( 3.8) in serum-free medium ( 5.8.3). This is very tedious, however, and as the various genes are cloned, production in prokaryotes or yeast is becoming more common. 

Some growth factors (e.g. PDGF) induce DNA synthesis in quiescent 3T3 cells when no other growth factors are present, while others (e.g. EGF and IGF) are required in combinations indicating that all factors do not act by a common mechanism (Rozengurt, 1986 Wakelam, 1989). 

Factors produced following ingestion of a bacterium with a lipopolysaccharide coat by a macrophage. Based on data in Old (1988) 

On stimulation of quiescent cells with growth factors or serum there is a rapid increase in the transmembrane flux of Na+, K+ and H+ and a mobilisation of Ca2+ from intracellular stores. The increase in Ca2+ concentration can be mimicked by treating cells with the Ca2+ ionophore, A23187. There quickly follows a series of events leading to changes in gene expression and cell structure and eventually to DNA replication and cell division. 

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