Circulating classical monocytes are associated with CD11c⁺ macrophages in human visceral adipose tissue

Immune cell accumulation in adipose tissue (AT) is associated with the development of AT inflammation, resulting in metabolic dysfunction. Circulating immune cell patterns may reflect immune cell accumulation in expanding AT. However, data linking human leukocytes in blood and AT is lacking. We investigated whether blood immune cell populations are associated with their counterparts in subcutaneous (scAT) or visceral AT (vAT). Flow cytometry was performed on blood, scAT and vAT from 16 lean and 29 obese men. Circulating natural killer (NK)-cells, classical monocytes and nonclassical monocytes were higher in obese individuals. vAT, but not scAT, of obese individuals contained more inflammatory CD11c⁺ "M1" macrophages and NK cells compared to lean individuals. Blood classical monocytes were associated with CD11c⁺ macrophages in vAT but not scAT. This association was unrelated to expression of the adhesion molecules CD11b and CD11c or of the chemokine receptor CX3CR1 on these monocytes. Other AT immune cells were not associated with their respective counterparts in blood. Finally, CD11c⁺ macrophages and CD4⁺ T-cells in vAT were associated with their counterparts in scAT. In conclusion, blood classical monocytes reflect CD11c⁺ macrophages in vAT.