Targeted Expression of Human CD1d in Transgenic Mice Reveals Independent Roles for Thymocytes and Thymic APCs in Positive and Negative Selection of Vα14i NKT Cells1
Targeted Expression of Human CD1d in Transgenic Mice Reveals Independent Roles for Thymocytes and Thymic APCs in Positive and Negative Selection of Vα14i NKT Cells1
复制标题
转基因小鼠中人 CD1d 的靶向表达揭示了胸腺细胞和胸腺 APC 在 Vα14i NKT 细胞的正向和负向选择中的独立作用1
作者：
J. Schümann;P. Pittoni;Elena Tonti;H. Macdonald;P. Dellabona;G. Casorati
CD 1d依赖性不变Vα14（Vα 14 i）NKT细胞是表达保守的半不变TCR的先天性T淋巴细胞，在小鼠中由主要与Vβ8.2和Vβ7配对的不变Vα14-Jα18 TCR α链组成。胸腺阳性和阴性选择Vα 14 i NKT细胞的细胞要求仅部分了解。因此，我们在胸腺细胞（主要是CD 4 + CD 8+双阳性）或APC（与Vα 14 i NKT细胞选择有关的细胞）上产生表达人CD 1d（hCD 1d）的转基因小鼠。在不存在内源性小鼠CD 1d（mCD 1d）的情况下，hCD 1d在胸腺细胞（而非APC）上的表达足以选择经Ag α-半乳糖基神经酰胺离体激活后证明具有功能的Vα 14 i NKT细胞。然而，在胸腺细胞上通过hCD 1d选择的Vα 14 i NKT细胞获得的数量低于对照小鼠，并且基本上表达Vβ8.2。胸腺细胞上hCD 1d选择的Vβ8.2+ Vα 14 i NKT细胞数量较少，但mCD 1d的伴随表达并未逆转，相反，mCD 1d恢复了Vβ7+ Vα 14 i NKT细胞的发育。在APC上同时表达hCD 1d和mCD 1d的小鼠中，Vβ8.2+（而非Vβ7+）NKT细胞发育受损。综上所述，我们的数据表明，胸腺细胞选择性表达CD 1d足以对功能性Vα 14 i NKT细胞进行阳性选择，而胸腺细胞和APC可能独立介导阴性选择。
CD1d-dependent invariant Vα14 (Vα14i) NKT cells are innate T lymphocytes expressing a conserved semi-invariant TCR, consisting, in mice, of the invariant Vα14-Jα18 TCR α-chain paired mostly with Vβ8.2 and Vβ7. The cellular requirements for thymic positive and negative selection of Vα14i NKT cells are only partially understood. Therefore, we generated transgenic mice expressing human CD1d (hCD1d) either on thymocytes, mainly CD4+ CD8+ double positive, or on APCs, the cells implicated in the selection of Vα14i NKT cells. In the absence of the endogenous mouse CD1d (mCD1d), the expression of hCD1d on thymocytes, but not on APCs, was sufficient to select Vα14i NKT cells that proved functional when activated ex vivo with the Ag α-galactosyl ceramide. Vα14i NKT cells selected by hCD1d on thymocytes, however, attained lower numbers than in control mice and expressed essentially Vβ8.2. The low number of Vβ8.2+ Vα14i NKT cells selected by hCD1d on thymocytes was not reversed by the concomitant expression of mCD1d, which, instead, restored the development of Vβ7+ Vα14i NKT cells. Vβ8.2+, but not Vβ7+, NKT cell development was impaired in mice expressing both hCD1d on APCs and mCD1d. Taken together, our data reveal that selective CD1d expression by thymocytes is sufficient for positive selection of functional Vα14i NKT cells and that both thymocytes and APCs may independently mediate negative selection.