CD81 and infection: Of all the PHH donor lots examined for sporozoite invasion and LS development, some lots were not supportive of either or both P. vivax and P. falciparum. We hypothesize this bimodal support of infection in otherwise healthy hepatocytes is a product of natural variation in presentation of hepatic surface receptors CD81 and SR-BI, as P. vivax and P. falciparum hepatocyte entry has been found receptor-specific61.