IL-7 regulates in vitro activity of CD8 + T cells in patients with sepsis through modulation of CD127 expression / 中华微生物学和免疫学杂志

ABSTRACT

Objective:To investigate the expression of membrane-bound CD127 (mCD127) and soluble CD127 (sCD127) in patients with sepsis, and to assess the mechanism of IL-7 in regulating CD8 + T cell activity in these patients. Methods:A prospective cohort study was conducted on 47 patients with sepsis (sepsis group) and 18 healthy controls (control group). Serum samples and peripheral blood mononuclear cells (PBMCs) were isolated. CD8 + T cells were purified. IL-7 and sCD127 levels in serum were measured by enzyme-linked immunosorbent assay. Expression of mCD127 on CD8 + T cells was measured by flow cytometry. Total CD127 and sCD127 expression at mRNA level in CD8 + T cells was semi-quantified by real-time PCR. CD8 + T cells were stimulated with recombinant human IL-7, along with signal transducer and activator of transcription 5 (STAT5) inhibitor or phosphatidylinositol 3-kinase (PI3K) inhibitor. Changes in mCD127 expression on CD8 + T cells and the expression of total CD127 and sCD127 at mRNA level were then measured. The cytotoxicity of CD8 + T cells in response to IL-7 stimulation was assessed using a co-culture system with CD8 + T cells and MCF-7 cells. Student′s t test and LSD- t test were used for statistical analysis. Results:Serum IL-7 and sCD127 were lower in sepsis group than in control group [(101.82±12.58) pg/ml vs (111.07±11.10) pg/ml, P<0.01; (278.58±62.31) pg/ml vs (334.62±70.55) pg/ml, P<0.01]. Serum IL-7 was positively correlated with serum sCD127 in patients with sepsis ( r=0.46, P<0.01). The percentage of mCD127 + CD8 + T cells in CD8 + T cells and the mean fluorescence intensity of mCD127 in sepsis group were higher than those in control group ( P<0.05). The expression of sCD127 at mRNA level in CD8 + T cells was lower in sepsis group than in control group (1.34±0.33 vs 1.80±0.60, P<0.001). Stimulation with recombinant human IL-7 promoted sCD127 secretion and total CD127 and sCD127 expression at mRNA level in CD8 + T cells ( P<0.05). Inhibition of STAT5 suppressed the IL-7-induced sCD127 secretion and total CD127 and sCD127 expression at mRNA level ( P<0.05). However, inhibition of PI3K could not achieve those effects ( P>0.05). CD8 + T cells-induced target cell death was inhibited in sepsis group as compared with that in control group [(12.49±2.12)% vs (23.83±3.76)%, P<0.001]. Recombinant human IL-7 promoted the CD8 + T cell-induced target cell death ( P<0.05) and increased the secretion of cytokines and cytotoxic granule proteins ( P<0.05). Inhibition of STAT5 suppressed IL-7-mediated CD8 + T cell cytotoxicity ( P<0.05). However, inhibition of PI3K did not affect IL-7-mediated CD8 + T cell cytotoxicity ( P>0.05). Conclusions:IL-7 promoted sCD127 secretion and enhanced the in vitro cytotoxicity of CD8 + T cells in patients with sepsis through STAT5 signal pathway.