Cassatt D R, Sweet R W, Arthos J A, Truneh A
Department of Cellular Biochemistry and Immunology, Smith Kline Beecham Pharmaceuticals, King of Prussia, PA 19406.
J Immunol. 1991 Sep 1;147(5):1470-6.
The T cell surface molecule CD4 (L3T4 in mouse) is important in the T lymphocyte response to Ag presented in association with MHC class II molecules. To examine the role of CD4 in immune function, we expressed a soluble form of murine CD4 by deleting the transmembrane and cytoplasmic regions of the L3T4 gene and transfecting the altered gene into Chinese hamster ovary cells. The recombinant soluble mouse CD4 (smCD4) retained the native conformation of the external portion, as indicated by the binding of L3T4 mAb. In vitro, smCD4 did not inhibit class II-dependent, Ag-specific, T cell proliferation or MLR, even at concentrations 300-fold greater, on a molar basis, than that of anti-CD4 mAb. Immunization of mice with smCD4 induced a strong anti-CD4 response. These antibodies showed some binding to native cell surface CD4, indicating that immunization with smCD4 generated an anti-self response. Analysis of lymphoid cells from spleen, lymph node, and thymus of smCD4-treated mice revealed no alteration in subset phenotypes. Also, Th cell function, as measured by response to soluble Ag, was not compromised. Thus, smCD4 did not inhibit T cell activity in vitro, and the autoimmune response arising from immunization with smCD4 had no apparent consequences for normal immune function.
T细胞表面分子CD4（小鼠中的L3T4）在T淋巴细胞对与MHC II类分子相关呈递的抗原的应答中起重要作用。为了研究CD4在免疫功能中的作用，我们通过缺失L3T4基因的跨膜区和胞质区并将改变后的基因转染到中国仓鼠卵巢细胞中，表达了一种可溶性形式的小鼠CD4。重组可溶性小鼠CD4（smCD4）保留了外部部分的天然构象，这通过L3T4单克隆抗体的结合得以表明。在体外，即使在摩尔浓度比抗CD4单克隆抗体高300倍的情况下，smCD4也不抑制II类依赖性、抗原特异性的T细胞增殖或混合淋巴细胞反应（MLR）。用smCD4免疫小鼠诱导了强烈的抗CD4反应。这些抗体显示出与天然细胞表面CD4有一定结合，表明用smCD4免疫产生了自身反应。对用smCD4处理的小鼠的脾脏、淋巴结和胸腺中的淋巴细胞进行分析，发现亚群表型没有改变。此外，通过对可溶性抗原的反应来衡量的Th细胞功能也未受损。因此，smCD4在体外不抑制T细胞活性，并且用smCD4免疫引起的自身免疫反应对正常免疫功能没有明显影响。
