Triantafilou K, Triantafilou M, Wilson K M, Fernandez N
Department of Biological Sciences, University of Essex, Colchester, United Kingdom.
Hum Immunol. 2000 Jun;61(6):585-98. doi: 10.1016/s0198-8859(00)00112-9.
We have investigated the homotypic associations of major histocompatibilty, class II and class I molecules using immunoprecipitation from detergent solubilised cell extracts. A 120-kDa structure corresponding to an HLA-DR dimer of dimers was immunoprecipitated by the HLA-DR specific mAb L243 from both biotinylated cell-surface and metabolically labeled B cells and transfectant fibroblasts. The thermostability of this structure in SDS was examined. It was detected at 4 degrees C, 22 degrees C, and 37 degrees C, but not at 50 degrees C or 100 degrees C. Experiments performed with L243 Fab fragments and with purified HLA-DR molecules, indicated the presence of HLA-DR dimers of dimers and single heterodimers on B cells. HLA-DQ was also found to form SDS-stable dimers of dimers and single heterodimers on the cell surface of B cells, demonstrating that HLA class II isotypes, other than HLA-DR, also form homotypic associations. Similar experiments performed with HLA class I specific mAb, W632, revealed the existence of a 90 kDa and a 135-kDa structure corresponding to a MHC class I multimers. Under the same conditions, non-MHC molecules such as CD14 were found not to self-associate. These findings indicate that major histocompatibility molecules have the intrinsic ability to form homotypic associations at the cell surface of antigen presenting cells.
我们使用从去污剂溶解的细胞提取物中进行免疫沉淀的方法，研究了主要组织相容性复合体II类和I类分子的同型缔合。一种对应于HLA-DR二聚体的120 kDa结构，可被HLA-DR特异性单克隆抗体L243从生物素化的细胞表面以及代谢标记的B细胞和转染的成纤维细胞中免疫沉淀出来。我们检测了该结构在SDS中的热稳定性。它在4℃、22℃和37℃时可被检测到，但在50℃或100℃时未被检测到。用L243 Fab片段和纯化的HLA-DR分子进行的实验表明，B细胞上存在HLA-DR二聚体的二聚体和单个异二聚体。还发现HLA-DQ在B细胞表面也形成SDS稳定的二聚体的二聚体和单个异二聚体，这表明除HLA-DR外，HLA II类同种型也形成同型缔合。用HLA I类特异性单克隆抗体W632进行的类似实验揭示了存在对应于MHC I类多聚体的90 kDa和13 kDa结构。在相同条件下，发现非MHC分子如CD14不会自我缔合。这些发现表明，主要组织相容性分子具有在抗原呈递细胞表面形成同型缔合的内在能力。
