RESUMEN
@#以程序性死亡因子 1（PD-1）及其配体 1（PD-L1）为代表的B7/CD28家族在肿瘤免疫治疗中显示出极大的应用潜力，但仍 有很多PD-L1检测阴性患者无法从中受益。作为B7家族成员，人内源性逆转录病毒-H长末端重复关联蛋白2 (HHLA2)分子结 构与PD-L1等其他B7家族成员有一定的同源性和相似性， 对T细胞有共刺激和共抑制作用，在多数实体肿瘤中呈高表达，且在某 些实体肿瘤中表达比PD-L1更广泛；其通过与受体穿膜和免疫球蛋白结构域2(TMIGD2)结合可促进肿瘤免疫逃逸，导致肿瘤的 进展和转移。基于此，HHLA2/TMIGD2有望成为肿瘤免疫治疗新的通路和靶点之一。本文就HHLA2及其受体TMIGD2的分子 结构、生物学功能及其在实体肿瘤中作用的研究进展作一综述。
RESUMEN
HHLA2 is a newly discovered B7 family member.HHLA2 appears to have limited expression in normal tissues.TMIGD,one of the receptors HHLA2 is established.Similar to HHLA2,TMIGD2 is absent in mouse and rat while it is found in human and higher primates.HHLA2 with inhibition of CD4 and CD8 T cell proliferation,but also can inhibit the role of T cells secrete some cytokines.HHLA2 protein is absent in most normal tissues,but mainly expressed on epithelial cells of a few tissues.But HHLA2 is widely expressed in various human cancers such as lung cancer,breast cancer and osteosarcoma et al,that make HHLA2 might be a new target for human cancers immunotherapy.