Effects of invariant natural killer T cell activation on prognosis in early sepsis / 第二军医大学学报

ABSTRACT

Objective To explore the effects of invariant natural killer T (iNKT) cell activation on inflammation and severity of early sepsis. Methods Healthy C57BL/6 male mice were randomly divided into 3 groups sham group, cecal ligation and puncture (CLP)-induced sepsis model group (CLP group) and CLP-induced sepsis model plus treatment with anti-CD1d blocking antibody group (anti-CD1d group). Flow cytometry was used to determine the frequencies of the iNKT cells in the peripheral blood, spleen and thymus of mice after 24 h of CLP operation. Meanwhile, the ELISA assay was used to detect the serum levels of tumor necrosis factor-α (TNF-α), interleukin (IL)-6, interferon-γ (IFN-γ) and IL-4. The correlation of iNKT cells and cytokine was analyzed. The bacterial colonies in peripheral blood and peritoneal lavage fluid were determined. The 10-day survival rates of mice after CLP operation were observed. Twenty patients with confirmed sepsis and 20 healthy volunteers aging 18-70 years were selected. The frequency of peripheral blood iNKT cells and serum cytokine levels of all patients and healthy volunteers were detected. Correlations of iNKT cells and cytokines, Acute Physiology and Chronic Health Evaluation Ⅱ (APACHE Ⅱ) scores in septic patients were analyzed. Results Compared with the sham group, the mice in the CLP group showed significantly more iNKT cells, significantly higher levels of TNF-α, IL-6, IFN-γ and IL-4 (P<0.05, P<0.01), and significantly higher levels of bacterial colonies in peripheral blood and peritoneal lavage fluid (P<0.01). The mice in the CLP group all died within 7 days after operation. In the mice of the anti-CD1d group, iNKT cell proportions in peripheral blood, spleen and thymus, the serum levels of TNF-α, IL-6, IFN-γ and IL-4 in peripheral blood, and the bacterial burden in the abdominal cavity were decreased compared with the CLP group (P<0.05, P<0.01). Four mice in anti-CD1d group survived at 10 days of post-operation. Compared with healthy volunteers, septic patients displayed significantly higher frequency of iNKT cells and significantly higher levels of TNF-α, IL-6, IFN-γ and IL-4 (P<0.05, P<0.01). Moreover, there was a positive correlation between frequency of iNKT cells with serum IFN-γ and IL-4 and the score of APACHE Ⅱ (P<0.05). Conclusion Increase of peripheral blood iNKT cells in early sepsis is associated with the severity and prognoses of sepsis, which suggests iNKT cells may play an important role in the inflammation of sepsis.