TIGIT/CD155通路在脓毒症DC功能障碍中的作用及机制研究

Dysfunction and dysmaturity of dendritic cell (DC) is one of the important causes of immunosuppression during sepsis. T cell Ig and ITIM domain (TIGIT) is a newly identified co-inhibitory receptor expressed on T cell，modulating function of DC by binding to CD155. However,the role of TIGIT/CD155 pathway in sepsis remains unknown. Our preliminary experiments showed that the expression of TIGIT on T cell and CD155 on DC of septic patients were both upregulated. Blocking the TIGIT/CD155 pathway in vitro promoted DC producing TNFα. In order to explore the potential role of TIGIT/CD155 pathway on dysfunction of DC during sepsis, we will examine the expression of TIGIT and CD155 on septic patients, CLP induced septic mice, and isolated DC lines by flow cytometry, siRNA，and adenovirus vector transfection. The correlations between the expression of TIGIT/CD155 and dysfunction of DC will be determined. We will further investigate the role of TIGIT/CD155 in DC dysfunction and dysmaturity as well as the underlying mechanism by upregulating or downregulating CD155 expressing on DC. All prior in vitro experiments will be validated in a murine CLP model by blocking antibodies. This current proposal will illustrate the role of TIGIT/CD155 pathway in dysfunction of DC during sepsis, so as to provide a new target and experimental evidence for therapy of sepsis-induced immunosuppression.

DC成熟障碍和功能低下是脓毒症免疫抑制的重要原因之一。TIGIT是新近发现的表达于T细胞上的共抑制受体，可与其配体CD155结合参与调控DC功能，但该新型共抑制通路在脓毒症中的作用尚不清楚。我们的预实验发现脓毒症患者DC表面CD155和T细胞表面TIGIT表达上调，体外阻断TIGIT/CD155通路可促进DC分泌TNFα。为探索TIGIT/CD155通路是否参与介导脓毒症时DC功能障碍，我们拟选择临床脓毒症患者、脓毒症小鼠及离体DC培养体系，采用流式细胞术、RNA干扰、腺病毒载体转染等手段分析脓毒症时T细胞和DC表面TIGIT/CD155表达，及其与DC功能的关系；探索上调或抑制CD155表达对DC功能的影响及可能机制；并在体验证阻断TIGIT/CD155通路对脓毒症小鼠DC成熟障碍和功能低下的影响,为未来通过TIGIT/CD155通路调节DC功能治疗脓毒症免疫抑制提供理论和实验依据。

脓毒症(sepsis)是机体对感染的反应失调而导致危及生命的器官功能障碍。脓毒症患者多器官衰竭是ICU住院患者主要死亡原因之一，尚缺乏有效的治疗措施。免疫抑制是脓毒症时细胞与分子层面机体反应失调的常见表现，其中一个重要原因是DC成熟障碍和功能低下。TIGIT是新近发现的表达于T细胞上的共抑制受体，可与其配体CD155结合参与调控DC功能，但该新型共抑制通路在脓毒症中的作用尚未见报道。在本研究中我们发现，脓毒症小鼠DC表面CD155和T细胞表面TIGIT表达上调，给予抗CD155抗体治疗可降低脓毒症小鼠血液及腹腔液中细菌数量，改善脓毒症小鼠的生存率。抗体中和CD155 可逆转脓毒症小鼠免疫抑制状态，提高其免疫功能；过表达CD155能够调节DC细胞因子的分泌，增加抑炎性细胞因子的表达，但不影响DC成熟。研究表明调节TIGIT/CD155通路对于治疗脓毒症免疫抑制具有重要意义，抗体中和CD155是逆转脓毒症免疫抑制、改善脓毒症患者治疗结局的潜在手段。本研究具有较重要的理论创新，该理论已发表于《Biochem Biophys Res Commun》，影响因子2.466。受本项目资助，共发表标记资助的论文3篇，均为SCI收录论著；协助培养博士生与硕士生各1名。