Figure 2

Comparison of HB3 platelet-mediated clumping frequencies detected by in vitro assays performed at a constant haematocrit (Ht) but varying parasitaemia (Pt). A. In vitro platelet-mediated clumping assays were set up at 2% Ht and varying Pt (1%, 4% and 12%) and the clumping frequency (percentage of IE in clumps out of at least 500 IE counted) was assessed by fluorescence microscopy of wet preparations at four time points (15 min, 30 min, 1 h and 2 h). The mean and standard deviation of three wet preparations from each time point are shown, and the range of clump sizes (number of IE forming the clumps) detected in each assay and each time point is indicated. Two replicates of each experiment, done on different days and with platelet-rich plasma from different donors, are shown. Each experiment included a negative control performed with PPP (platelet-poor plasma) and 12% Pt to determine the potential for non-platelet mediated clumping. B. As above but at 5% Ht. C. As above but at 10% Ht.