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. 2009 Mar 20;5(3):e1000349. doi: 10.1371/journal.ppat.1000349

Figure 4. Plasma ADAMTS13 activity inhibition in P. falciparum malaria.

Figure 4

(A&B) To investigate further the mechanisms responsible for the marked and discrepant increase in plasma VWF∶CB, and the significant reduction in ADAMTS13 activity, we investigated the effects of mixing malaria plasma with normal plasma. Plasma from four different children (□, •, ▵, ⧫) with SM (each with baseline ADAMTS13 activities of ∼0.4 U/dl) were mixed in various proportions with pooled normal plasma, and ADAMTS13 activity determined. No evidence of an immediate ADAMTS13 inhibitor effect was observed (Fig 4A). However following incubation at 37°C for 15 min or 30 min (Fig 4B), significant ADAMTS13 inhibition was observed in malaria plasmas at either 75%∶25% (▴), or 50%∶50% (•), but not in normal control plasma (□). All results represent mean±SEM. (C) To further investigate whether malarial plasma contained an ADAMTS13 inhibitor, individual malaria plasma samples (n = 4) and control plasmas (n = 4) were spiked with recombinant human ADAMTS13. Again, significant inhibition of rADAMTS13 activity (means±SEM) was observed only in malaria plasma (⧫) but not in normal plasma (▪).