Monocyte subsets in human liver disease show distinct phenotypic and functional characteristics.
Liver fibrosis is a wound healing response to chronic liver injury and inflammation in which macrophages and infiltrating monocytes participate in both the development and resolution phase. In humans, three monocyte subsets have been identified: the classical CD14++CD16-, intermediate CD14++CD16+, and nonclassical CD14+CD16++ monocytes. We studied the phenotype and function of these monocyte subsets in peripheral blood and liver tissue from patients with chronic inflammatory and fibrotic liver diseases. The frequency of intrahepatic monocytes increased in disease compared with control liver tissue, and in both nondiseased and diseased livers there was a higher frequency of CD14++CD16+ cells with blood. Our data suggest two nonexclusive mechanisms of CD14++CD16+ accumulation in the inflamed liver: (1) recruitment from blood, because more than twice as many CD14++CD16+ monocytes underwent transendothelial migration through hepatic endothelial cells compared with CD14++CD16- cells; and (2) local differentiation from CD14++CD16- classical monocytes in response to transforming growth factor β and interleukin (IL)-10. Intrahepatic CD14++CD16+ cells expressed both macrophage and dendritic cell markers but showed high levels of phagocytic activity, antigen presentation, and T cell proliferation and secreted proinflammatory (tumor necrosis factor α, IL-6, IL-8, IL-1β) and profibrogenic cytokines (IL-13), chemokines (CCL1, CCL2, CCL3, CCL5), and growth factors (granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor), consistent with a role in the wound healing response.


CONCLUSIONS
Intermediate CD14++CD16+ monocytes preferentially accumulate in chronically inflamed human liver as a consequence of enhanced recruitment from blood and local differentiation from classical CD14++CD16- monocytes. Their phagocytic potential and ability to secrete inflammatory and profibrogenic cytokines suggests they play an important role in hepatic fibrogenesis.
Centre for Liver Research and NIHR Biomedical Research Unit in Liver Disease, Institute of Biomedical Research, University of Birmingham, Birmingham, United Kingdom.
Evaggelia
E
Liaskou
Henning W
HW
Zimmermann
Ka-Kit
KK
Li
Ye H
YH
Oo
Shankar
S
Suresh
Zania
Z
Stamataki
Omar
O
Qureshi
Patricia F
PF
Lalor
Jean
J
Shaw
Wing-kin
WK
Syn
Stuart M
SM
Curbishley
David H
DH
Adams
D016207:Cytokines / Q000378:metabolism; D058851:GPI-Linked Proteins / Q000378:metabolism; D006801:Humans; D018950:Lipopolysaccharide Receptors / Q000378:metabolism; D008103:Liver Cirrhosis / Q000276:immunology; D008107:Liver Diseases / Q000276:immunology*; D009000:Monocytes / Q000473:pathology* / Q000502:physiology; D010641:Phenotype; D017452:Receptors, IgG / Q000378:metabolism
D016207:Cytokines; C428200:FCGR3B protein, human; D058851:GPI-Linked Proteins; D018950:Lipopolysaccharide Receptors; D017452:Receptors, IgG