The blood platelets contribution to innate host defense - what they have learned from their big brothers

Matthias Klinger (1)

1 Institute of Anatomy

Bactericidal effects of blood platelets are known for more than 120 years, but the underlying mechanisms are largely obscure. Keeping in mind structural and functional analogies of platelets to neutrophiles, three different mechanisms are thinkable: Engulfment of pathogens, release of microbicidal proteins, and production of reactive oxygen species (ROS). Here, we focus on the release of ROS and a possible contribution of blood plasma and thrombin to the bactericidal effects. Killing of bacteria was evaluated by DNA fluorescence labeling and electron microscopy. Release of ROS by platelets was measured photometrically by cytochrom C and phenolred/peroxidase assays and was further evaluated by topological methods. We found that (1) platelets produce 1500 times less O2- and 4000 times less H2O2 compared to neutrophils, (2) ROS do not effect the killing rates, (3) no local enrichment of ROS was detectable. On the other hand, thrombin and plasma proteins with a MW >100 kDa are essential for bactericidal effects. We suggest that platelets contribute to the innate host defence by providing a catalytical surface for synthesis of thrombin. In the presence of a heat-instable plasma protein, thrombin may generate a strong bactericidal complex, which is only effective in close vicinity to the platelet membrane.

Mots clés: Life Sciences

Matthias Klinger. The blood platelets contribution to innate host defense - what they have learned from their big brothers. Biotechnology Journal, 2009, 4 (6), pp.914. ⟨10.1002/biot.200800362⟩. ⟨hal-00490110⟩