RECOGNITION OF LIGANDS BY SPECIFIC CYTOTOXIC T LYMPHOCYTES & NATURAL KILLER CELL

由NK细胞和T细胞亚群表达的CD 94/NKG 2受体已经被认为是广泛的经典和非经典HLA I类分子的受体。为了检查CD 94/NKG 2蛋白的配体特异性，产生了可溶性异源二聚体形式的受体，并用于与表达确定的HLA I类/肽复合物的细胞的直接结合研究。我们证实了CD 94/NKG 2A与HLA-E特异性相互作用，并证明这种相互作用依赖于HLA-E与肽的结合。此外，通过可溶性受体的直接结合或使用CD 94/NKG 2A + NK细胞的功能测定，未观察到CD 94/NKG 2A与经典HLA I类分子之间的相互作用。还评估了与HLA-E相关的肽在HLA-E与CD 94/NKG 2A之间的相互作用中的作用。所有检测的I类前导序列肽均与HLA-E结合，并被CD 94/NKG 2A识别。然而，I类前导序列的氨基酸变异影响HLA-E的稳定性。此外，并非所有检测的HLA-E/肽复合物均被CD 94/NKG 2A识别。因此，HLA-E的CD 94/NKG 2A识别在两个水平上受肽控制;首先，肽必须稳定HLA-E并促进细胞表面表达，其次，HLA-E/肽复合物必须形成CD 94/NKG 2A的配体。测定了CD 94胞内结构域的晶体结构，揭示了独特的C型凝集素折叠。该晶体结构可能是其他NK细胞受体如Ly-49、NKR-P1和CD-69的原型。在来自表达H-2（B）基因和小型猪I类转基因（PD 1）的转基因小鼠的原代胚胎成纤维细胞中，用腺病毒12转化导致所有I类复合物的组装和细胞表面表达的抑制。PD 1的细胞表面表达可以通过用肽转运蛋白基因转染细胞来恢复。然而，H-2K（B）基因表达的重建还需要H-2K（B）mRNA的稳态水平增加2倍，这可以通过用干扰素处理细胞或用H-2K（B）基因转染细胞来实现。I类分子的生物发生的详细分析揭示了游离I类重链的稳态表达，其即使在肽转运蛋白基因过表达时也不转化为整合的复合物。- 自然杀伤（NK）细胞、HLA I类受体、HLA-E、CD 94/NKG 2、MHC I类复合物、肽结合、癌症

The CD94/NKG2 receptors expressed by subpopulations of NK cells and T cells have been implicated as receptors for a broad range of both classical and nonclassical HLA class I molecules. To examine the ligand specificity of CD94/NKG2 proteins, a soluble heterodimeric form of the receptor was produced and used in direct binding studies with cells expressing defined HLA class I/peptide complexes. We confirmed that CD94/NKG2A specifically interacts with HLA-E and demonstrated that this interaction is dependent on the association of HLA-E with peptide. Moreover, no interaction between CD94/NKG2A and classical HLA class I molecules were observed, as assayed by direct binding of the soluble receptor or by functionalassays using CD94/NKG2A+ NK cells. The role of the peptide associated with HLA-E in the interaction between HLA-E and CD94/NKG2A was also assessed. All class I leader sequence peptides tested bound to HLA-E and were recognized by CD94/NKG2A. However, amino acid variations in class I leader sequences affected the stability of HLA-E. Additionally, not all HLA-E/peptide complexes examined were recognized by CD94/NKG2A. Thus CD94/NKG2A recognition of HLA-E is controlled by peptide at two levels; first, peptide must stabilize HLA- E and promote cell surface expression and second, the HLA-E/peptide complex must form the ligand for CD94/NKG2A. The crystal structure of the intracellular domain of CD94 was determined revealing a unique C- type lectin fold. The crystal structure is likely a prototype for other NK cell receptors such as Ly-49, NKR-P1 and CD-69.In primary embryonal fibroblasts from transgenic mice expressing H-2(b) genes and a miniature swine class I transgene (PD1), transformation with adenovirus 12 results in suppression of assembly and cell surface expression of all class I complexes. Cell surface expression of PD1 can be recovered by transfecting the cells with peptide transporter genes. However, reconstitution of the H-2K(b) gene expression requires, in addition, a 2-fold increase in the steady state level of the H-2K(b) mRNA that can be attained by treatment of the cells with interferons or by transfecting them with the H-2K(b) gene. A detailed analyses of the biogenesis of class I molecules has revealed the steady state expression of free class I heavy chains that are not converted into conformed complexes even when peptide transporter genes are overexpressed. - Natural Killer (NK) cells, HLA class I receptors, HLA- E, CD94/NKG2, MHC class I complexes, peptide binding, cancer