In vitro regulatory effects of IL-18 on natural killer-like B cells in patients with primary hepatocellular carcinoma / 中华微生物学和免疫学杂志

ABSTRACT

Objective:To investigate the changes in peripheral blood and liver-infiltrating natural killer-like B (NKB) cells in patients with primary hepatocellular carcinoma (HCC), and to assess the influence of IL-18 on NKB cells in vitro and the underlying mechanism. Methods:Forty-three HCC patients and 21 normal controls (NC) were enrolled in the study. Peripheral blood samples were collected to isolate plasma and peripheral blood mononuclear cells (PBMC). Intrahepatic lymphocytes (IHL) were isolated from tumor tissues and para-tumor tissues obtained from 16 HCC patients who received surgery. IL-12, IL-18 and IL-18 binding protein (IL-18BP) levels in plasma were measured by enzyme linked immunosorbent assay. The percentages of CD3 -NKp46 + CD19 + NKB cells and IL-18 + NKB cells in PBMC and IHL were analyzed by flow cytometry. Changes in the percentages of NKB cells and IL-18 + NKB cells were measured after stimulating PBMC and IHL with recombinant human IL-18 (1 ng/ml and 10 ng/ml). Changes in IL-18BP levels in the culture supernatants and phosphorylated nuclear factor-κB (NF-κB) in NKB cells were also assessed. Student′s t test, one-way analysis of variance or LSD-t test was used for statistical analysis. Results:There was no significant difference in plasma IL-12 level between HCC patients and NC ( P=0.245). Compared with NC, HCC patients had decreased IL-18 level in plasma [(224.3±58.89) pg/ml vs (327.0±52.27) pg/ml, P<0.000 1], but increased IL-18BP level [(4.421±0.97) ng/ml vs (0.92±0.18) ng/ml, P<0.000 1]. The percentages of peripheral blood NKB cells and IL-18 + NKB cells were lower in HCC patients than in NC [(2.68±1.23)% vs (8.88±2.95)% and (54.42±12.60)% vs (69.74±12.65)%, both P<0.000 1]. The percentage of NKB cells in IHL was reduced in tumor tissues as compared with that in para-tumor tissues [(2.89±0.86)% vs (4.66±1.17)%, P<0.000 1]. Moreover, the percentage of IL-18 + NKB cell was also down-regulated in tumor tissues as compared with that in para-tumor tissues [(51.50±13.18)% vs (62.13±9.24)%, P=0.013]. Recombinant human IL-18 stimulation reduced the IL-18BP level in the culture supernatants ( P<0.05). IL-18 stimulation at 1 ng/ml did not affect NKB cell percentage, IL-18 + NKB cell percentage or NF-κB phosphorylation in NKB cells from PBMC or IHL ( P>0.05), while 10 ng/ml of IL-18 not only elevated NKB cell percentage and IL-18+ NKB cell percentage, but also promoted NF-κB phosphorylation in NKB cells ( P<0.01). Conclusions:In vitro stimulation with high concentration of IL-18 might promote NF-κB phosphorylation by inhibition of IL-18BP expression. This process might play a positive feedback role to induce the activation of NKB cells and IL-18 secretion.