8, 9 Rosetting has been associated with severe malaria in multiple African study sites (reviewed in Rowe et al.10), potentially because it leads to enhanced parasitised RBC sequestration and decreased blood flow in post-capillary venules.11, 12 CR1 acts as a receptor for P. falciparum RBC invasion via its interaction with the parasite ligand P. falciparum reticulocyte-binding-like homologue protein 4.4, 5, 6, 7. The gene discussed is CR1; the disease is malaria.