http://en.wikipedia.org/wiki/Monocyte
There are at least three types of monocytes in human blood:
a) the classical monocyte is characterized by high level expression of the CD14 cell surface receptor (CD14++ CD16- monocyte)
b) the non-classical monocyte shows low level expression of CD14 and additional co-expression of the CD16 receptor (CD14+CD16++ monocyte).
c) the intermediate monocyte with high level expression of CD14 and low level expression of CD16 (CD14++CD16+ monocytes).
Ghattas et al. state that the "intermediate" monocyte population is likely to be a unique subpopulation of monocytes, as opposed to a developmental step, due to their comparatively high expression of surface receptors involved in reparative processes(including vascular endothelial growth factors type 1 and 2, CXCR4, and Tie-2) as well as evidence that the "intermediate" subset is specifically enriched in the bone marrow.After stimulation with microbial products the CD14+CD16++ monocytes produce high amounts of pro-inflammatory cytokines like tumor necrosis factor and interleukin-12. Said et al. showed that activated monocytes express high levels of PD-1 which might explain the higher expression of PD-1 in CD14+CD16++ monocytes as compared to CD14++CD16- monocytes. Triggering monocytes-expressed PD-1 by its ligand PD-L1 induces IL-10 production which activates CD4 Th2 cells and inhibits CD4 Th1 cell function.
There are at least three types of monocytes in human blood:
a) the classical monocyte is characterized by high level expression of the CD14 cell surface receptor (CD14++ CD16- monocyte)
b) the non-classical monocyte shows low level expression of CD14 and additional co-expression of the CD16 receptor (CD14+CD16++ monocyte).
c) the intermediate monocyte with high level expression of CD14 and low level expression of CD16 (CD14++CD16+ monocytes).
Ghattas et al. state that the "intermediate" monocyte population is likely to be a unique subpopulation of monocytes, as opposed to a developmental step, due to their comparatively high expression of surface receptors involved in reparative processes(including vascular endothelial growth factors type 1 and 2, CXCR4, and Tie-2) as well as evidence that the "intermediate" subset is specifically enriched in the bone marrow.After stimulation with microbial products the CD14+CD16++ monocytes produce high amounts of pro-inflammatory cytokines like tumor necrosis factor and interleukin-12. Said et al. showed that activated monocytes express high levels of PD-1 which might explain the higher expression of PD-1 in CD14+CD16++ monocytes as compared to CD14++CD16- monocytes. Triggering monocytes-expressed PD-1 by its ligand PD-L1 induces IL-10 production which activates CD4 Th2 cells and inhibits CD4 Th1 cell function.
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