Expression of Fas/FasL in CD8+ T and CD3+ Foxp3+ Treg Cells - Relationship with Apoptosis of Circulating CD8+ T Cells in Hepatocellular Carcinoma Patients

Aims: Dysfunction of the host immune system in cancer patients can be due to a number of factors, includinglymphocyte apoptosis. Several studies showed that Foxp3+T cells take part in inducing this process by expressingFasL in tumor patients. However, the relationship between apoptosis, CD8+T cells and Foxp3+T cells in HCCpatients is still unclear. The present study was designed to investigate the correlation between apoptosis levelsand Fas/FasL expression in CD8+T lymphocytes and Foxp3+T cells in patients with HCC.
Methods: CD8+T cellsand CD3+Foxp3+T cells were tested from peripheral blood of HCC patients and normal controls and subjectedto multicolor flow cytometry. The expression of an apoptosis marker (annexin V) and the death receptor Fas inCD8+T cells and FasL in CD3+Foxp3+T cells were evaluated. Serum TGF-β1 levels in patients with HCC weremeasured by enzyme-linked immunosorbent assay. The relationship between apoptosis and Fas expression, aswell as FasL expression in CD3+Foxp3+T cells was then evaluated.
Results: The frequency of CD8+T cells bindingannexin V and Fas expression in CD8+T cells, were all higher in HCC patients than normal controls and theproportion of apoptotic CD8+T cells correlated with their Fas expression. Serum TGF-β1 levels correlated inverselywith CD3+Foxp3+T cells.
Conclusions: Fas/FasL interactions might lead to excessive turnover of CD8+T cellsand reduce anti-tumor immune responses in patients with HCC. Further investigations of apoptosis inductionin Fas+CD8+T cells in vitro are required.