Co-culture of BeWo cells with P. falciparum -infected erythrocytes. Parasites were either cultured normally (alone) or with BeWo-ST. Parasitaemia after 24 hrs in cultures initiated with (A) 0.2% parasitaemia or (B) 2% parasitaemia. Parasitaemia after 48 hrs in cultures initiated with (C) 0.2% or (D) 2% parasitaemia. Results are means percent parasitaemia ± SD for triplicate samples determined by flow cytometry. Horizontal lines indicate initial parasitaemia.