Sportsman J R, Park M M, Cheresh D A, Fukuda M, Elder J H, Fox R I
J Immunol. 1985 Jul;135(1):158-64.
A cell surface antigen (gp140) was previously shown to exist on T cell subsets as well as on monocytes and macrophages in normal peripheral blood. Elevated expression of this antigen was associated with immune system disorders, acute lymphocytic leukemias, and in vitro activation of T cells. The antigen could be identified with monoclonal antibody (MAb) T305. Gp140 was a biosynthetic product of T cells because it could be labeled with [3H]leucine or [3H] glucosamine. Biochemical studies of gp140 used high performance liquid chromatography with nitrocellulose blotting to isolate aliquots suitable for 125I radiolabeling and immunoprecipitation to demonstrate: a) a reduction in m.w. of gp140 KD to 90 KD after deglycosylation by trifluoromethanesulfonic acid, b) alteration of isoelectric point from 4.1 to 5.7 after neuraminidase treatments, c) absence of N-linked sugars based on resistance to endoglycosidase F, d) resistance to trypsin and chymotrypsin digestion but susceptibility to pronase, and e) presence of sialic acid and lactosaminoglycan as O-linked sugars. Gp140 could be labeled with the periodate/NaB[3H]4 technique, indicating its similarity to a class of sialoglycoproteins previously described on activated T-cells in mouse and man. The antigenic epitope recognized by MAb T305 contains sialic acid linked (2----3) to galactose; however, periodate oxidation of the exocyclic ring of sialic acid did not affect binding by MAb T305. In an attempt to determine the functional role of gp140, we tested the ability of MAb T305 to block: a) proliferation of peripheral blood lymphocytes to mitogens, b) response to interleukin 2 (IL 2) of an IL 2 dependent T cell line, and c) growth of a T-ALL derived cell line. No inhibition of proliferation or growth was noted. Although the function of gp140 remains unknown, its association with lymphocyte activation and certain disease states suggests that it may provide a target for modulation of the immune response. These studies characterize the structural features of gp140 and further define the epitope recognized by MAb T305.
先前研究表明，一种细胞表面抗原（gp140）存在于正常外周血中的T细胞亚群以及单核细胞和巨噬细胞上。该抗原的表达升高与免疫系统紊乱、急性淋巴细胞白血病以及T细胞的体外激活有关。该抗原可用单克隆抗体（MAb）T305识别。Gp140是T细胞的生物合成产物，因为它可用[3H]亮氨酸或[3H]葡糖胺进行标记。对gp140的生化研究采用高效液相色谱结合硝酸纤维素印迹法，以分离适合125I放射性标记和免疫沉淀的等分试样，结果表明：a）经三氟甲磺酸去糖基化后，gp140 KD的分子量降至90 KD；b）经神经氨酸酶处理后，等电点从4.1变为5.7；c）基于对内切糖苷酶F的抗性，不存在N-连接糖；d）对胰蛋白酶和糜蛋白酶消化具有抗性，但对链霉蛋白酶敏感；e）存在唾液酸和乳糖胺聚糖作为O-连接糖。Gp140可用高碘酸盐/NaB[3H]4技术进行标记，这表明它与先前在小鼠和人类活化T细胞上描述的一类唾液糖蛋白相似。MAb T305识别的抗原表位含有与半乳糖连接（2----3）的唾液酸；然而，唾液酸外环的高碘酸盐氧化并不影响MAb T305的结合。为了确定gp140的功能作用，我们测试了MAb T305阻断以下方面的能力：a）外周血淋巴细胞对有丝分裂原的增殖；b）IL 2依赖性T细胞系对白细胞介素2（IL 2）的反应；c）T-ALL衍生细胞系的生长。未观察到增殖或生长受到抑制。尽管gp140的功能仍然未知，但其与淋巴细胞激活和某些疾病状态的关联表明，它可能为调节免疫反应提供一个靶点。这些研究表征了gp140的结构特征，并进一步确定了MAb T305识别的表位。
