Walcheck B, Watts G, Jutila M A
Veterinary Molecular Biology, Montana State University, Bozeman 59717.
J Exp Med. 1993 Sep 1;178(3):853-63. doi: 10.1084/jem.178.3.853.
E-Selectin is an inducible adhesion protein expressed by endothelial cells and recognized by leukocytes during their extravasation from the blood into inflamed tissues. Originally, E-selectin was defined as a myeloid cell-specific adhesion protein, but recent studies have shown it to be recognized by human lymphocytes as well. These lymphocytes represent a memory T cell subset and have been shown to express the HECA-452 carbohydrate epitope (CLA+ lymphocytes). We extend these findings and show that ruminant gamma/delta T cells bind E-selectin as well; and we provide preliminary evidence that this interaction is mediated by a novel glycoprotein receptor on the lymphocyte. Unlike conventional T cells (alpha/beta T cells), gamma/delta T cells from neonatal and mature animals bind E-selectin, suggesting that prior antigen stimulation and differentiation to a memory lymphocyte are not required for this interaction. Neuraminidase treatment of the gamma/delta T cells or addition of ethylenediaminetetraacetic acid (EDTA) to the assay abrogates binding, demonstrating the importance of sialic acid and divalent cations, which is consistent with other E-selectin-mediated adhesion events. However, previously defined E-selectin carbohydrate ligands, such as sialyl Lewis x on neutrophils and the HECA-452 epitope on human memory lymphocytes, are antigenically different than the carbohydrates on ruminant gamma/delta T cells since the mAbs CSLEX and HECA-452 do not recognize these cells. Protease treatment of gamma/delta T cells significantly inhibits their binding to E-selectin; however, previously characterized adhesion glycoproteins, such as L-selectin, CD44, and CD18, are not involved in the adhesive event. An E-selectin affinity column purifies a single glycoprotein of 250 kD (280 kD under reducing conditions) from gamma/delta T cell detergent lysates. Neuraminidase digestion of the 250-kD product as well as EDTA abolishes binding to E-selectin. Finally, E-selectin expression in vivo appears to mediate gamma/delta T cell accumulation. Stimulation of bovine skin with tumor necrosis factor alpha induced an increase in E-selectin expression that was associated with an influx of gamma/delta T cells at the same site.
E选择素是一种可诱导的黏附蛋白，由内皮细胞表达，在白细胞从血液外渗进入炎症组织的过程中被白细胞识别。最初，E选择素被定义为一种髓样细胞特异性黏附蛋白，但最近的研究表明它也能被人类淋巴细胞识别。这些淋巴细胞代表记忆性T细胞亚群，并且已被证明表达HECA-452碳水化合物表位（CLA+淋巴细胞）。我们扩展了这些发现，并表明反刍动物γ/δT细胞也能结合E选择素；并且我们提供了初步证据表明这种相互作用是由淋巴细胞上一种新的糖蛋白受体介导的。与传统T细胞（α/βT细胞）不同，新生动物和成熟动物的γ/δT细胞都能结合E选择素，这表明这种相互作用不需要先前的抗原刺激和向记忆性淋巴细胞的分化。用神经氨酸酶处理γ/δT细胞或在检测中加入乙二胺四乙酸（EDTA）会消除结合，这证明了唾液酸和二价阳离子的重要性，这与其他E选择素介导的黏附事件一致。然而，先前定义的E选择素碳水化合物配体，如中性粒细胞上的唾液酸化路易斯x和人类记忆性淋巴细胞上的HECA-452表位，在抗原性上与反刍动物γ/δT细胞上的碳水化合物不同，因为单克隆抗体CSLEX和HECA-452不能识别这些细胞。用蛋白酶处理γ/δT细胞会显著抑制它们与E选择素的结合；然而，先前鉴定的黏附糖蛋白，如L选择素、CD44和CD18，不参与黏附事件。一个E选择素亲和柱从γ/δT细胞去污剂裂解物中纯化出一种250kD（还原条件下为280kD）的单一糖蛋白。对250-kD产物进行神经氨酸酶消化以及加入EDTA都会消除与E选择素的结合。最后，体内E选择素的表达似乎介导γ/δT细胞的聚集。用肿瘤坏死因子α刺激牛皮肤会导致E选择素表达增加，这与同一部位γ/δT细胞的流入有关。
