Rosenberg H F, Tiffany H L
Laboratory of Host Defenses, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892.
J Leukoc Biol. 1994 Oct;56(4):502-6. doi: 10.1002/jlb.56.4.502.
Monoclonal antibodies EG1 and EG2 have the unique ability to distinguish the storage from the secreted forms of the eosinophil cationic protein (ECP). EG2 has been used extensively as a marker for activated, secreting eosinophils, despite the fact that no biochemical differences between the storage and secreted forms of ECP have been identified. We have determined that the activation-specific EG2 detects only one of three distinct glycosylated forms of ECP (18 kDa); in contrast, both EG1 and polyclonal anti-ECP antiserum can detect three glycosylated forms of this protein (18, 20, and 22 kDa). We have also determined that EG2 detects fully deglycosylated ECP as well as fully deglycosylated eosinophil-derived neurotoxin. Our results indicate that activation-specific EG2 recognizes a polypeptide epitope that is masked in the higher-molecular-weight, more heavily glycosylated forms of ECP. These findings suggest that deglycosylation may occur in conjunction with activation and secretion; alternatively, the 18-kDa form of ECP may be present in the storage granule of resting eosinophils but may remain undetected in an inaccessible location or conformation.
单克隆抗体EG1和EG2具有独特的能力，能够区分嗜酸性粒细胞阳离子蛋白（ECP）的储存形式和分泌形式。尽管尚未确定ECP的储存形式和分泌形式之间存在生化差异，但EG2已被广泛用作活化的、分泌性嗜酸性粒细胞的标志物。我们已经确定，活化特异性的EG2仅能检测到ECP（18 kDa）三种不同糖基化形式中的一种；相比之下，EG1和多克隆抗ECP抗血清都能检测到该蛋白的三种糖基化形式（18、20和22 kDa）。我们还确定，EG2能检测到完全去糖基化的ECP以及完全去糖基化的嗜酸性粒细胞衍生神经毒素。我们的结果表明，活化特异性的EG2识别的多肽表位在分子量更高、糖基化程度更高的ECP形式中被掩盖。这些发现表明，去糖基化可能与活化和分泌同时发生；或者，18 kDa形式的ECP可能存在于静息嗜酸性粒细胞的储存颗粒中，但可能因位于难以接近的位置或构象而未被检测到。
