Carotid artery plaque uptake of (11)C-PK11195 inversely correlates with circulating monocytes and classical CD14(++)CD16(−) monocytes expressing HLA-DR

BACKGROUND: We explored the relation between blood concentrations of monocyte/lymphocyte subsets and carotid artery plaque macrophage content, measured by positron emission tomography (PET) with (11)C-PK11195. METHODS AND RESULTS: In 9 patients with carotid plaques we performed (11)C-PK11195-PET/computed tomography angiography imaging and measurement of absolute concentrations and frequencies of circulating monocytes and T-cell subsets. Plaque standardized uptake value (SUV) for (11)C-PK11195 was negatively correlated with concentrations of total monocytes (r = −0.58, p = 0.05) and CD14(++)CD16(−)HLA-DR(+) classical subset (r = −0.82, p = 0.005). These correlations hold true also in relation to plaque target to background ratio. No correlation was observed between plaque SUV and CD3(+)T lymphocytes, CD4(+)T lymphocytes nor with activated CD3(+)CD4(+)T cells expressing HLA-DR. CONCLUSIONS: We first demonstrated a reduction in the absolute concentration of monocytes and particularly in classical monocytes expressing HLA-DR in the presence of an increased uptake of (11)C-PK11195 in carotid plaques. The present work, despite being a pilot study comprising only a small number of subjects provides new insights in the search for specific cellular biomarkers with potential diagnostic and prognostic value in patients with a known carotid plaque.