α-半乳糖神经酰胺活化肺iNKT细胞诱导气道免疫耐受及其机制探讨

课题组发现α-半乳糖神经酰胺（α-GalCer）活化肺恒定自然杀伤（iNK）T细胞不诱导野生型小鼠产生气道炎症，但小鼠肺CD4+FoxP3+T细胞数量增加，同时α-GalCer不诱导缺乏iNKT细胞的CD1d KO小鼠肺CD4+FoxP3+T细胞数量增加。由于调节性T细胞可以诱导气道免疫耐受，防止机体发生Th2反应，故假设α-GalCer活化肺iNKT细胞通过诱导调节性T细胞介导气道免疫耐受。课题组初步发现α-GalCer活化肺iNKT细胞时，小鼠肺IL-2表达水平增加。由于IL-2可以诱导产生调节性T细胞，故假设α-GalCer活化肺iNKT细胞通过IL-2诱导机体产生调节性T细胞。为此，以野生型小鼠，CD1d、Jα18、CNS1 和IL-2 KO小鼠及人源化免疫重建SCID小鼠为实验动物，探讨α-半乳糖神经酰胺活化肺iNKT细胞是否通过IL-2诱导机体产生调节性T细胞介导气道免疫耐受。

Invariant natural killer T (iNKT) cells display substantial functional heterogeneity, and there is growing evidence, particularly in mouse models of asthma, showing that interactions between iNKT cells and regulatory T cells (Treg cells) play an important role in induction of tolerance in many different settings to lead to the prevention of diverse disease conditions such as autoimmunity, type 1 diabetes and transplant rejection. In our previous study, α-galactosylceramide (α-GalCer) administration via intraperitoneal injection can activate iNKT cells in the lung from normal wild-type BALB/c mice, but the activation of iNKT cells alone cannot induce airway inflammation without ovalbumin immunization and challenge. Meanwhile, the number of CD4+FoxP+Treg cells significantly increase in the lung, as accompanied with the activation of lung iNKT cells by intraperitoneal injection of α-GalCer in normal wild-type mice. In addition, it was found that intraperitoneal injection of α-GalCer can not results in increase of the lung CD4+FoxP+Treg cells in CD1d knockout-BALB/c mice, which lack iNKT cells, compared with wild-type BALB/c mice. It is well known that Treg cells play a vital role in inducing and maintaining airway immune tolerance, and thereby preventing Th2 response. As a result, it was hypothesized that α-GalCer-activated lung iNKT cells generate CD4+Foxp3+ regulatory T cells to induce airway tolerance. In our preliminary study, α-GalCer-activated lung iNKT cells can significantly enhance the concentration of interleukin-2 (IL-2) in bronchial alveolar lavage fluid (BALF) and the expression of IL-2 mRNA in the lung tissue from wild-type BALB/c mice, compared with CD1d knockout-BALB/c mice. IL-2 can drive the development of CD4+FoxP3+ regulatory T cells, which have suppresser function and mediate immune tolerance. As such, it was hypothesized that α-GalCer-activated lung iNKT cells generate CD4+Foxp3+ regulatory T cells through interleukin-2. For the purpose, wild-type BALB/c mice, CD1d knockout-BALB/c mice, Jα18 knockout-C57BL/6 mice, CNS1 knockout-BALB/c mice, IL-2 knockout-BALB/c mice and humanized mice of immune reconstitution using severe combined immunodeficiency (SCID) mice were used as experiment animals to investigate that α-GalCer-activated lung iNKT cells generate CD4+Foxp3+ regulatory T cells to induce airway tolerance through interleukin-2. Therefore, a better understanding of this immunoregulatory network will add to the ability to optimize iNKT cell-based therapeutics.