Schematic representation of the adhesion of P falciparum-infected erythrocytes to blood capillaries in the human placenta. A variant of PfEMP1 encoded by the var2CSA gene, expressed on the surface of infected erythrocytes, binds to CSA, a component of the proteoglycan matrix on placenta. PfEMP1 is presented in knob-like protrusions, and sequestration of infected erythrocytes in the placenta is believed to result in maternal malaria, a severe syndrome associated with low birth weight, prematurity, and chronic intervillositis. Higher receptor density (CSA) leads to greater binding and cooperativity as measured by functionalized membranes model system in vitro.¹