Читать книгу Neonatal Haematology - Barbara J. Bain, Irene Roberts - Страница 16

Normal erythropoiesis, the production of red blood cells, is crucial to early embryonic and fetal development. Most of our knowledge about the cells and genes involved in this process derives either from mouse models or from inherited anaemias, particularly in children. Almost all the characteristic features of red blood cells are different in the fetus and the newborn compared with their adult counterparts. These differences are even greater in preterm neonates and are directly relevant to our understanding of neonatal anaemias. The differences in erythropoiesis during fetal development are summarised in Table 1.1 and those that are important for our understanding of neonatal anaemias are discussed below.

Table 1.1 Features of fetal and neonatal red cells compared with adult red cells

Haemoglobin production	Embryonic haemoglobins (globin chains) Gower 1 (ζ2ε2) Gower 2 (α2ε2) Portland (ζ2γ2) Fetal haemoglobin (globin chains) Fetal haemoglobin (α2γ2) Adult haemoglobins (globin chains) Haemoglobin A (α2β2) lower Haemoglobin A2 (α2δ2) considerably lower
Red cell membrane	Gives resistance to osmotic lysis Altered expression of receptors (e.g. insulin) Increased lipid content and altered phospholipid profile More prone to oxidative damage Altered glucose transport Weak expression of A, B and I blood group antigens Increased variation in red cell shape (poikilocytosis) Red cell ‘pocks’ due to hyposplenism
Red cell metabolism	Glycolytic pathway Increased glucose consumption Altered enzyme levels, e.g. low 2,3‐DPG and PFK Pentose phosphate pathway Increased susceptibility to oxidant‐induced injury Lower level of glutathione peroxidase Reduced ability to generate NADPH

2,3‐DPG, 2,3‐diphosphoglycerate; NADPH, nicotinamide adenine dinucleotide phosphate; PFK, phosphofructokinase.