Morrow D M, Xiong N, Getty R R, Ratajczak M Z, Morgan D, Seppala M, Riittinen L, Gewirtz A M, Tykocinski M L
Institute of Pathology, Case Western Reserve University, Cleveland, Ohio 44106-4943.
Am J Pathol. 1994 Dec;145(6):1485-95.
Placental protein 14 (PP14), an immunosuppressive molecule previously known to be expressed in the female and male reproductive tracts only, was shown to be expressed by hematopoietic cells of the megakaryocytic lineage. Northern blot analysis confirmed the induction specificity of PP14 mRNA in phorbol ester-treated K562 cells. Potent immunosuppressive activity in conditioned medium from phorbol ester-treated K562 cells was attributed to hematopoietic PP14 by anti-PP14 antibody blocking. Immunoprecipitation with anti-PP14 antibodies from conditioned medium revealed two distinct PP14 protein isoforms, designated PP14.1 and PP14.2. Polymerase chain reaction cloning and analysis demonstrated the presence of distinct mRNA counterparts to PP14.1 and PP14.2 that had not been resolved by Northern blot analyses. Hematopoietic PP14.1 mRNA corresponds in size to endometrial PP14 mRNA, whereas the smaller hematopoietic PP14.2 mRNA displays an internal in-frame 66-nucleotide deletion that can be explained by alternative splicing and predicts a 22-amino-acid deletion in the encoded gene product. Both PP14 mRNA isoforms were additionally detected by reverse transcriptase polymerase chain reaction analyses in two human megakaryocytic cell lines and in normal human megakaryocytes and platelets. PP14 mRNA was not detected by reverse transcriptase polymerase chain reaction in a panel of nonhematopoietic, nonendometrial tissues examined. The finding of hematopoietic PP14 within the megakaryocytic lineage provides an additional regulatory link between the coagulation and immune systems in normal and pathological settings.
胎盘蛋白14（PP14）是一种免疫抑制分子，此前已知仅在雌性和雄性生殖道中表达，现发现巨核细胞系的造血细胞也可表达。Northern印迹分析证实了佛波酯处理的K562细胞中PP14 mRNA的诱导特异性。佛波酯处理的K562细胞条件培养基中的强效免疫抑制活性可通过抗PP14抗体阻断归因于造血PP14。用抗PP14抗体对条件培养基进行免疫沉淀，发现了两种不同的PP14蛋白异构体，分别命名为PP14.1和PP14.2。聚合酶链反应克隆和分析表明，存在与PP14.1和PP14.2不同的mRNA对应物，Northern印迹分析未解析出这些对应物。造血PP14.1 mRNA的大小与子宫内膜PP14 mRNA相对应，而较小的造血PP14.2 mRNA显示有一个66个核苷酸的框内内部缺失，这可以通过可变剪接来解释，并预测编码基因产物中有一个22个氨基酸的缺失。通过逆转录聚合酶链反应分析，在两个人巨核细胞系以及正常人巨核细胞和血小板中也额外检测到了这两种PP14 mRNA异构体。在一组检测的非造血、非子宫内膜组织中，逆转录聚合酶链反应未检测到PP14 mRNA。在巨核细胞系中发现造血PP14，为正常和病理情况下凝血系统和免疫系统之间提供了一个额外的调节联系。
