Human whole blood was collected and red blood cells were lysed with an erythrocyte lysing agent (ACK). Immune cells were stained for cell surface TSPO and the following immune cell markers: CD14 to identify monocytes, CD16 to identify neutrophils, CD3, CD4, and CD8 to identify T cells, CD19 to identify B cells, and CD56 and CD57 to identify NK cells. The percentage of surface TSPO positivity was calculated within each individual immune cell population, the average of at least 2 independent experiments with 16 individual human donors is shown. Values are mean ± SEM.