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. 2013 Jun 21;10(8):1053-60.
doi: 10.7150/ijms.6223. Print 2013.

FasL Expression on Human Nucleus Pulposus Cells Contributes to the Immune Privilege of Intervertebral Disc by Interacting With Immunocytes

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Free PMC article

FasL Expression on Human Nucleus Pulposus Cells Contributes to the Immune Privilege of Intervertebral Disc by Interacting With Immunocytes

Zhi-Heng Liu et al. Int J Med Sci. .
Free PMC article

Abstract

The mechanisms of immune privilege in human nucleus pulposus (NP) remain unclear. Accumulating evidence indicates that Fas ligand (FasL) might play an important role in the immune privilege of the disc. We aimed for addressing the role of FasL expression in human intervertebral disc degeneration (IDD) and immune privilege in terms of the interaction between NP cells and immunocytes via the FasL-Fas machinery. We collected NP specimens from 20 patients with IDD as degenerative group and 8 normal cadaveric donors as control. FasL expression was detected by qRT-PCR, western blotting and flow cytometry (FCM). We also collected macrophages and CD8(+) T cells from the peripheral blood of patients with IDD for co-cultures with NP cells. And macrophages and CD8(+) T cells were harvested for apoptosis analysis by FCM after 2 days of co-cultures. We found that FasL expression in mRNA, protein and cellular resolutions demonstrated a significant decrease in degenerative group compared with normal control (p<0.05). FCM analysis found that human NP cells with increased FasL expression resulted in significantly increased apoptosis ratio of macrophages and CD8(+) T cells. Our study demonstrated that FasL expression tends to decrease in degenerated discs and FasL plays an important role in human disc immune privilege, which might provide a novel target for the treatment strategies for IDD.

Keywords: CD8+ T cell.; FasL; immune privilege; intervertebral disc degeneration; macrophage.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interest exists.

Figures

Fig 1
Fig 1
FasL expression of NP cells in different levels from degenerative and normal NP. A. qRT-PCR analysis of FasL expression. B. Western blotting detection of FasL expression. C. Flow cytometry detection of FasL positive cells. Data are representative of six independent experiments. Error bars represent SEM. *p<0.05.
Fig 2
Fig 2
NP cells, macrophages and CD8+T cells from patients with intervertebral disc degeneration were detected. A. Cultured NP cells for 14 days. Scale bars = 500 µm. B. Cultured macrophages for 7 days from peripheral blood of patients with disc degeneration. Scale bars = 50 µm. C. Brightfield (left) and fluorescent (right) microscopy of human NP cells 96 h following transfection with lentivirus labeled with green fluorescent protein. Scale bars = 20 µm.
Fig 3
Fig 3
Flow cytometry apoptosis analysis of immunocytes after co-cultures. A. Contour diagram of Annexin V-FITC/PI FCM of human NP cells. The graphs stand for typical results of cell apoptosis; values represent the means for three experiments. B. Comparison of apoptotic cells in various macrophages groups (*p<0.05). Data are representative of three experiments. Error bars represent SEM. C. Comparison of apoptotic cells in various CD8+T cell groups (*p<0.05). Data are representative of three experiments. Error bars represent SEM.

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