Heterozygous sickle cell anemia give protection against –
Correct Answer: Malaria
Description: Adult red cells contain mainly HbA along with small amounts of HbA2 and foetal Hemoglobin HbF.Sickle cell hemoglobin is HbS.some are heterozygous for HbS called as sickle cell trait.In them only about half of HbA is replaced by HbS. Parasite densities(falciparum malaria) are relatively lower in heterozygous due to 1-Metabolically active intracellular parasites consume oxygen and decrease intracellular pH,both of which promote Hb sickling in AS red cells.These distoed and stiffened cells may be cleared more rapidly by phagocytes in spleen and liver helping to keep parasite load down. 2-Sickling impairs the formation of membrane knobs containing a protein made by the parasite called PfEMP-1.These membrane knobs are implicated in adhesion of infected red cells to endothelium which is believed to have an impoant pathogenic role in the most severe form of the disease cerebral malaria. Ref:Robbins and Cotran Pathologic basis of disease , South Asia Edition -9 volume 1 Page no.63
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