Girgrah N, Letarte M, Becker L E, Cruz T F, Theriault E, Moscarello M A
Department of Biochemistry, Hospital for Sick Children, Toronto, Ontario, Canada.
J Neuropathol Exp Neurol. 1991 Nov;50(6):779-92. doi: 10.1097/00005072-199111000-00009.
The CD44 antigen is a proteoglycan recently implicated in several adhesion events including that of lymphocytes to endothelium. The CD44 antigen, reactive with monoclonal antibody (MAb) 44D10, has been shown previously to be expressed in normal human white matter homogenates and to be found at higher concentrations in brain homogenates of victims of multiple sclerosis (MS). The cellular localization of CD44 in human brain of normal individuals and in those afflicted with MS has now been determined. Monoclonal antibody 44D10 reacted with astrocyte-like cells in 40 microns thick paraformaldehyde-fixed sections but not in thin (6 microns) fixed sections. A double labeling experiment performed on a frozen brain section with MAb 44D10 and rabbit anti-glial fibrillary acidic protein (GFAP), a cytoplasmic marker of astrocytes, confirmed the co-localization of these two antigens. The reactivity with brain tissue sections of a rabbit antiserum produced against lymphocyte-CD44 could be absorbed by a preparation of the CD44 glycoprotein, purified 2,100-fold from a white matter homogenate. The antiserum was shown by Western blot analysis to be specific for p80 glycoprotein in brain extracts derived from a normal and MS patients. This antibody reacted with fibrous astrocytes predominantly in white matter; staining was also noted in subependymal and subpial regions. Inhibition studies using a cellular radioimmunoassay indicated that the highest concentrations of CD44 in three MS victims were found in plaques, followed by periplaques and non-involved areas of white matter which were higher than normal white matter. Reactive astrocytes, identified in active lesions, expressed high levels of CD44 on their surfaces. Thus, CD44 is associated with astrocytes in human brain and the increased expression observed in MS brain may reflect activation and/or proliferation of astrocytes implicated in the pathogenesis of this disease.
CD44抗原是一种蛋白聚糖，最近发现它参与了包括淋巴细胞与内皮细胞黏附在内的多种黏附过程。与单克隆抗体（MAb）44D10反应的CD44抗原，先前已被证明在正常人脑白质匀浆中表达，并且在多发性硬化症（MS）患者的脑匀浆中浓度更高。现在已经确定了CD44在正常人和MS患者大脑中的细胞定位。单克隆抗体44D10在40微米厚的多聚甲醛固定切片中与星形胶质细胞样细胞反应，但在薄（6微米）固定切片中不反应。用MAb 44D10和兔抗胶质纤维酸性蛋白（GFAP，星形胶质细胞的细胞质标记物）对冷冻脑切片进行的双重标记实验证实了这两种抗原的共定位。用针对淋巴细胞CD44产生的兔抗血清与脑组织切片的反应性可被从白质匀浆中纯化2100倍的CD44糖蛋白制剂吸收。通过蛋白质印迹分析表明，该抗血清对来自正常人和MS患者的脑提取物中的p80糖蛋白具有特异性。该抗体主要与白质中的纤维性星形胶质细胞反应；在室管膜下和软脑膜下区域也观察到染色。使用细胞放射免疫测定的抑制研究表明，三名MS患者中CD44的最高浓度出现在斑块中，其次是斑块周围和未受累的白质区域，这些区域高于正常白质。在活动性病变中鉴定出的反应性星形胶质细胞在其表面表达高水平的CD44。因此，CD44与人脑星形胶质细胞相关，在MS脑中观察到的表达增加可能反映了与该疾病发病机制有关的星形胶质细胞的激活和/或增殖。
