Abstract
Sickle cell anaemia (SCA) results from a single mutation in the β globin gene. It is seldom symptomatic in the first semester of life. We analysed the expression pattern of 9 adhesion molecules on red blood cells, in a cohort of 54 SCA and 17 non-SCA very young infants of comparable age (median 144days, 81–196). Haemoglobin F (HbF) level was unsurprisingly elevated in SCA infants (41.2%±11.2) and 2–4 fold higher than in non-SCA infants, yet SCA infants presented significantly decreased Hb level and increased reticulocytosis. Cytometry analysis evidenced a specific expression profile on reticulocytes of SCA infants, with notably an increased expression of the adhesion molecules Lu/BCAM, ICAM-4 and LFA-3, both in percentage of positive cells and in surface density. No significant difference was found on mature red cells. Our findings demonstrate the very early onset of reticulocyte membrane modifications in SCA asymptomatic infants and allow an insight into the first pathological changes with the release of stress reticulocytes expressing a distinctive profile of adhesion molecules.
Highlights
Sickle cell anaemia (SCA) is caused by a mutation in the β globin gene
Mean Haemoglobin F (HbF) level in SCA infants was 41.2% (±11.2), a value 2–4 fold higher than reference values (10.4% ± 1.8)
Median Hb level in SCA infants was 9.1 g/dL (6.5–12), a value significantly decreased in comparison with non-SCA infants (11 g/dL, 7.2– 12.6, P b 0.001) whilst median reticulocyte percentage was increased in SCA infants (2.9%, 0.5–10 vs 2%, 0.5–4.2, P = 0.04)
Summary
Sickle cell anaemia (SCA) is caused by a mutation in the β globin gene. Sickle haemoglobin (HbS) polymerises when deoxygenated, resulting in red cell membrane rigidity and surface protein modifications that subsequently contribute to vaso-occlusion. It is considered that abnormal red blood cell (RBC) adhesiveness in SCA through activation, sustained or increased expression of adhesion molecules is pivotal in the genesis of vaso occlusive crisis, the hallmark of SCA (Hebbel et al, 1980). We analysed the expression pattern of 9 adhesion molecules on both reticulocytes and mature RBCs in SCA and non-SCA very young infants. These markers are known surface molecules, which allow characterisation of erythroid maturation and/or which are adhesion molecules demonstrated to play an important pathophysiological role (Cartron and Elion, 2008).
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