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Published on: January 3, 2012
Alteration in the rheologic properties of Plasmodium knowlesi--infected red cells. A possible mechanism for capillary
Abstract:
Red cells parasitized by Plasmodium knowlesi concentrate within the microcirculation of many organs including cerebral capillaries in rhesus monkeys. The possibility that P. knowlesi could alter the rheologic properties of red cells so that they are trapped within capillaries was investigated in the present study. The viscosity of P. knowlesi-infected red cells suspended in Ringer's solution was increased at all shear rates at hematocrits above 30%. At moderate parasitemia the resistance to flow through 5 mu polycarbonate sieves was increased; at high parasitemia the pores were obstructed. Mature trophozoites caused more obstruction than young trophozoites (rings) at any given level of parasitemia. The reduction of deformability of red cells infected by schizonts of P. knowlesi was further demonstrated by their exclusion from rouleaux in a plasma suspension. Therefore, the red cells infected by P. knowlesi become less deformable, and this reduction in red cell deformability may explain the obstruction of cerebral capillaries.
Insights
Plasmodium knowlesi infection reduces red blood cell deformability, increasing blood viscosity. This may explain how infected cells obstruct cerebral capillaries, impacting blood flow.
Area of Science:
- Parasitology
- Hematology
- Microcirculation
Background:
- Plasmodium knowlesi infects red blood cells, leading to their accumulation in organ microvasculature.
- Cerebral capillary obstruction is a potential complication of Plasmodium knowlesi infections.
Purpose of the Study:
- To investigate if Plasmodium knowlesi alters red blood cell rheology, causing capillary obstruction.
- To determine the relationship between parasitemia levels and red blood cell deformability.
Main Methods:
- Measuring the viscosity of infected red blood cells at various shear rates and hematocrits.
- Assessing flow resistance through micro-sieves with infected red blood cells.
- Observing red blood cell deformability using rouleaux formation in plasma.
Main Results:
- Increased blood viscosity in infected red blood cells at hematocrits above 30%.
- Elevated flow resistance and pore obstruction in micro-sieves, particularly at high parasitemia.
- Reduced red blood cell deformability, especially with mature trophozoites and schizonts.
Conclusions:
- Plasmodium knowlesi infection significantly reduces red blood cell deformability.
- Decreased red blood cell deformability is a likely mechanism for cerebral capillary obstruction in knowlesi malaria.
