Department of Physiology, Osaka Medical College, Takatsuki, Osaka-fu 569-8686, Japan.
Gene. 2010 Apr 1;454(1-2):31-8. doi: 10.1016/j.gene.2010.01.007. Epub 2010 Feb 1.
We previously reported that a population of allograft (H-2D(d)K(d))-induced macrophages (AIM) in C57BL/6 (H-2D(b)K(b)) mice exhibited major histocompatibility complex (MHC) haplotype (H-2D(d) or H-2K(d))-specific killing of allografts in a macrophage MHC receptor 1 or 2 (MMR1 or 2)-dependent manner. In the present study, we isolated a cDNA encoding a human homologue (83.6% amino-acid identity) of mouse MMR2 from a human cDNA library, the donors of which had never been allografted. The cDNA (2376-bp) encoded a 791-amino-acid polypeptide with a calculated molecular mass of 91kDa. Unexpectedly, the mRNA was expressed at least in part in peripheral blood mononuclear cells (PBMCs) or monocytes, but not in granulocytes or lymphocytes. The expression varied from volunteer to volunteer: PBMCs from 8 volunteers expressed human MMR2 at similar levels, whereas those from 8 other volunteers showed no or much less expression of it. Flow cytometric analyses revealed that HEK293T cells expressing human MMR2 protein bound fluorescein-labeled HLA-B62, but not A2, A-11, A-24 or B7, with a dissociation constant (=8.9x10(-9)M) and that the interaction was completely inhibited by the addition of R12 mAb specific for mouse MMR2. Similarly, the expression of mouse MMR2 varied from strain to strain in mice: PBMCs from 9 non-H-2K(d), but not from 3 H-2K(d), mice expressed mouse MMR2 specific for H-2K(d). These results suggest that human MMR2 on monocytes may be a novel receptor for HLA-B62.
我们之前曾报道，在 C57BL/6（H-2D(b)K(b)）小鼠中，一种同种异体（H-2D(d)K(d)）诱导的巨噬细胞（AIM）群体以巨噬细胞 MHC 受体 1 或 2（MMR1 或 2）依赖性方式表现出对同种异体移植物的 MHC 单倍型（H-2D(d)或 H-2K(d)）特异性杀伤。在本研究中，我们从人类 cDNA 文库中分离出编码小鼠 MMR2 同源物（83.6%氨基酸同一性）的 cDNA，其供体从未进行过同种异体移植。该 cDNA（2376bp）编码一个 791 个氨基酸的多肽，计算的分子量为 91kDa。出乎意料的是，mRNA 至少部分在外周血单核细胞（PBMC）或单核细胞中表达，但不在粒细胞或淋巴细胞中表达。表达因人而异：8 名志愿者的 PBMC 以相似水平表达人 MMR2，而其他 8 名志愿者的表达水平则较低或几乎不表达。流式细胞术分析表明，表达人 MMR2 蛋白的 HEK293T 细胞与荧光素标记的 HLA-B62 结合，但不与 A2、A-11、A-24 或 B7 结合，解离常数（=8.9x10(-9)M），并且该相互作用可被特异性针对鼠 MMR2 的 R12 mAb 完全抑制。同样，在小鼠中，MMR2 的表达也因品系而异：9 只非 H-2K(d)小鼠而非 3 只 H-2K(d)小鼠的 PBMC 表达特异性针对 H-2K(d)的鼠 MMR2。这些结果表明，单核细胞上的人 MMR2 可能是 HLA-B62 的一种新型受体。
