Mallett S, Fossum S, Barclay A N
MRC Cellular Immunology Unit, Sir William Dunn School of Pathology, University of Oxford, UK.
EMBO J. 1990 Apr;9(4):1063-8. doi: 10.1002/j.1460-2075.1990.tb08211.x.
The antigen recognized by the monoclonal antibody (mAb) MRC OX40 is present on activated rat CD4 positive T lymphocytes but not other cells. cDNA clones were isolated from an expression library using the MRC OX40 mAb and the protein sequence for the OX40 antigen deduced. It contains a typical signal sequence and a single putative transmembrane sequence of 25 predominantly hydrophobic amino acids giving an extracellular domain of 191 amino acids and a cytoplasmic domain of 36 amino acids. The sequence of the extracellular domain includes a cysteine-rich region with sequence similarities with the low affinity nerve growth factor receptor (NGFR) of neurons and the CD40 antigen present on human B cells. Within this region three cysteine-rich motifs can be recognized in OX40 compared with four similar motifs in both NGFR and CD40. OX40, CD40 and NGFR constitute a new superfamily of molecules with expression including lymphoid cells (OX40, CD40) and neuronal cells (NGFR). This is reminiscent of the immunoglobulin superfamily whose molecules are variously found at the surface of lymphoid or brain cells or both.
单克隆抗体（mAb）MRC OX40识别的抗原存在于活化的大鼠CD4阳性T淋巴细胞上，而不存在于其他细胞上。利用MRC OX40单克隆抗体从一个表达文库中分离出cDNA克隆，并推导了OX40抗原的蛋白质序列。它包含一个典型的信号序列和一个由25个主要为疏水氨基酸组成的单一推定跨膜序列，产生一个191个氨基酸的细胞外结构域和一个36个氨基酸的细胞质结构域。细胞外结构域的序列包括一个富含半胱氨酸的区域，该区域与神经元的低亲和力神经生长因子受体（NGFR）和人B细胞上存在的CD40抗原具有序列相似性。与NGFR和CD40中的四个相似基序相比，在OX40中可以识别出三个富含半胱氨酸的基序。OX40、CD40和NGFR构成了一个新的分子超家族，其表达包括淋巴细胞（OX40、CD40）和神经元细胞（NGFR）。这让人联想到免疫球蛋白超家族，其分子在淋巴细胞或脑细胞表面或两者表面均有不同程度的存在。
