Bilsland C A, Diamond M S, Springer T A
Center for Blood Research, Harvard Medical School, Boston, MA 02115.
J Immunol. 1994 May 1;152(9):4582-9.
p150,95 is a member of the leukocyte integrin family of adhesion proteins. Compared with LFA-1 and Mac-1, p150,95 is less well functionally characterized. Although p150,95 has complement receptor activity for iC3b and has been designated complement receptor type 4, transfected cells expressing p150,95 do not bind iC3b-sensitized cells. We report that cells cotransfected with a human p150,95 alpha subunit and a chicken, but not human, beta subunit bind IgM-iC3b-coated erythrocytes, suggesting that interactions between the alpha and beta subunits can regulate p150,95 adhesiveness. Furthermore, purified human p150,95 binds to cell-bound iC3b-coated erythrocytes. Because binding to iC3b by cellular and purified p150,95 is specifically abolished by mAbs that localize to the I domain of p150,95, we suggest that the I domain of the p150,95 alpha subunit is an important ligand recognition site for iC3b.
p150,95是粘附蛋白白细胞整合素家族的成员。与淋巴细胞功能相关抗原-1（LFA-1）和巨噬细胞抗原-1（Mac-1）相比，p150,95的功能特性了解较少。尽管p150,95对iC3b具有补体受体活性，并已被指定为4型补体受体，但表达p150,95的转染细胞并不结合iC3b致敏细胞。我们报告，共转染人p150,95α亚基和鸡（而非人）β亚基的细胞可结合IgM-iC3b包被的红细胞，这表明α亚基和β亚基之间的相互作用可调节p150,95的粘附性。此外，纯化的人p150,95可结合细胞结合的iC3b包被的红细胞。由于定位到p150,95 I结构域的单克隆抗体可特异性消除细胞和纯化的p150,95与iC3b的结合，我们认为p150,95α亚基的I结构域是iC3b的重要配体识别位点。
