Objective: To score the number of plaque neutrophils and relate the score to plaque morphology and inflammatory status.
Methods and results: Neutrophils are inflammatory cells with tissue destruction capabilities that have been found at the site of an atherosclerotic plaque rupture or erosion. Poor evidence exists for neutrophil infiltration in human carotid atherosclerotic plaques, and its association with plaque morphology has not yet been described. A set of 355 human carotid plaques was stained for the neutrophil marker CD66b. High neutrophil numbers were found in plaques with a large lipid core, high macrophage numbers, and low collagen amount and smooth muscle cell numbers. High neutrophil numbers were associated with high interleukin 8 (P<0.001) and matrix metalloproteases 8 (P=0.005) and 9 (P<0.001) plaque levels. High microvessel density within plaques was correlated with high neutrophil numbers (P=0.01). In addition, low numbers of neutrophils were associated with female sex and use of beta-blockers.
Conclusions: For the first time to our knowledge, these results show that neutrophil numbers are strongly associated with the histopathologic features of rupture-prone atherosclerotic lesions and suggest a role for neutrophils in plaque destabilization.