Summary
Neutrophils are important cellular sources of interleukin (IL) 17A and –F. Moreover,
upon activation neutrophils are able to excrete chromatin embedded with components
from their cytoplasmic granules to form ‘neutrophil extracellular traps’ (NETs). Recent
studies suggested that NETs contribute to thrombosis by promoting fibrin deposition
and platelet aggregation. IL17A may also promote thrombosis by enhancing platelet
aggregation. In the present study we investigated the presence of neutrophils, NETs
and IL17A and –F in coronary thrombosuction specimens obtained from patients after
acute myocardial infarction. Neutrophils and NETs were identified using histochemical
(H&E, Feulgen procedure) and immunohistochemical stainings (Histone H1, myeloperoxidase,
neutrophil elastase) in 15 fresh, 15 lytic and 15 organised thrombi. The presence
and distribution of IL17A and –F was studied using (immuno)histochemical double staining
and spectral image analysis, rtPCR and Western blot. High numbers of neutrophils are
present (10–30% of the thrombus mass) in fresh and lytic, but not in organized thrombus.
NETs were frequently observed in fresh (4/15) and lytic (12/15), but never in organised
thrombus specimens. Double staining combining the Feulgen reaction with Histone- H1,
MPO or neutrophil elastase confirmed colocalisation with DNA. Cytoplasmatic IL17A/F
staining was found in the majority of the neutrophils, extracellularly and in NETs.
Western blotting confirmed the presence of IL17A and IL17F in thrombus specimens.
In conclusion, a large burden of neutrophils, neutrophil extracellular traps and IL17A
and –F are important constituents of fresh and lytic thrombus after acute myocardial
infarction. The specific colocalisation of these indicates a role during thrombus
stabilisation and growth.