Figure 5: Schematic drawing depicting influence of M1 or M2 monocyte activation on arginase 1 and NOS2 expression, NO production, and adherence of parasitized RBC to endothelium. | Scientific Reports

Figure 5: Schematic drawing depicting influence of M1 or M2 monocyte activation on arginase 1 and NOS2 expression, NO production, and adherence of parasitized RBC to endothelium.

From: Monocyte polarization in children with falciparum malaria: relationship to nitric oxide insufficiency and disease severity

Figure 5

Monocytes (M) acted upon by various cytokines differentiate to (A) M1-like cells (“classically activated”) or (B) M2-like cells (“alternatively activated”). M1 cells can produce NOS2 that converts arginine to nitric oxide (NO) (A). M2 cells can produce arginase 1 that converts arginine to ornithine (ORN) and urea (B), causing depletion of arginine and reduction of NO. NO decreases expression of endothelial cell adhesion molecules (EC-CAM) (e.g., ICAM-1 and VCAM-1), and absence of NO or low NO causes increased CAM expression. RBC expressing P. falciparum-encoded proteins such as PfEMP1 bind to EC-CAM (B) causing blockage of blood flow and distal tissue ischemia. NO reduces EC-CAM expression, increases RBC deformability, and increases vascular reactivity.

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