In Plasmodium falciparum malaria, the ring forms are seen in peripheral blood smears but mature trophozoites and schizonts are typically absent. The reason is:
- A Mature stages are destroyed by spleen before reaching peripheral blood
- B PfEMP1 (P. falciparum erythrocyte membrane protein 1) expressed on infected RBCs causes cytoadherence to deep vascular endothelium (sequestration), removing mature parasites from circulation ✓
- C Mature trophozoites are too large to pass through pulmonary capillaries
- D The mature stages undergo premature apoptosis within the RBC
Correct answer: B. PfEMP1 (P. falciparum erythrocyte membrane protein 1) expressed on infected RBCs causes cytoadherence to deep vascular endothelium (sequestration), removing mature parasites from circulation
Explanation
P. falciparum-infected RBCs express PfEMP1 on their surface from the trophozoite stage onwards. PfEMP1 binds to endothelial receptors (CD36, ICAM-1, CSA in placenta) causing sequestration of mature-stage parasitised RBCs in deep microvascular beds. This explains why only ring forms are seen in peripheral blood and is directly responsible for the pathogenesis of cerebral malaria, placental malaria, and severe organ dysfunction — these deep sequestered parasites are not sampled by peripheral smear. Spleen destruction is not the mechanism.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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