Up-regulation of soluble TNF receptors, TNFR I (a) and TNFR II (b), released into the supernatant from human umbilical vein endothelial cells, after co-culture with Plasmodium falciparum strain ItG-infected and uninfected red blood cells (PRBC and RBC, respectively) for 20 h, determined by ELISA. Expressed as mean concentration ± SEM, from four separate experiments.