Aakhus A M, Stavem P, Hovig T, Pedersen T M, Solum N O
Research Institute for Internal Medicine, Rikshospitalet, University of Oslo, Norway.
Br J Haematol. 1990 Mar;74(3):320-9. doi: 10.1111/j.1365-2141.1990.tb02590.x.
A 70-year-old patient with a life-long bleeding tendency, giant platelets and thrombocytopenia (10-40 x 10(9) platelets/l) has been studied. This is a condition often associated with lack of platelet membrane glycoprotein Ib (GP Ib). Electron microscopy of fixed platelets incubated with monoclonal antibodies to GP Ib (AN 51, AP 1) and gold-labelled goat anti-mouse IgG, showed a distinct distribution of GP Ib on the patient's platelets, however. Crossed immunoelectrophoresis and SDS-PAGE demonstrated a reduced mobility of the patient's GP Ib which could be explained by absence of sialic acid. Blotting with peroxidase-conjugated peanut agglutinin confirmed this conclusion. This lectin binds to galactose-N-acetyl-galactosamine residues exposed terminally when sialic acid is absent from the carbohydrate side-chains. Such binding could be seen with normal GP Ib only after neuraminidase treatment. Fluorescence studies with FITC-conjugated peanut agglutinin showed binding of the lectin to intact patient platelets, indicating that lack of sialic acid was not introduced during the platelet isolation procedure. Neither could the lack of sialic acid be attributed to increased neuraminidase activity as studied in vitro. Platelets treated with neuraminidase in vivo or in vitro are rapidly cleared from the circulation. Therefore the patient's thrombocytopenia may be associated with the reduced amount of GP Ib sialic acid. As far as we know, similar cases have not been described previously.
对一名70岁、有终生出血倾向、存在巨大血小板和血小板减少症（血小板计数为10 - 40×10⁹个/升）的患者进行了研究。这种情况常与血小板膜糖蛋白Ib（GP Ib）缺乏有关。然而，用抗GP Ib单克隆抗体（AN 51、AP 1）和金标山羊抗小鼠IgG孵育固定血小板后的电子显微镜检查显示，GP Ib在该患者血小板上有明显分布。交叉免疫电泳和SDS - PAGE显示该患者的GP Ib迁移率降低，这可以用唾液酸缺失来解释。用辣根过氧化物酶标记的花生凝集素进行印迹分析证实了这一结论。当碳水化合物侧链中没有唾液酸时，这种凝集素会与末端暴露的半乳糖 - N - 乙酰半乳糖胺残基结合。只有在神经氨酸酶处理后，正常的GP Ib才能出现这种结合。用异硫氰酸荧光素标记的花生凝集素进行荧光研究显示，该凝集素与完整的患者血小板结合，表明在血小板分离过程中没有引入唾液酸缺失的情况。体外研究也表明，唾液酸缺乏也不能归因于神经氨酸酶活性增加。体内或体外经神经氨酸酶处理的血小板会迅速从循环中清除。因此，该患者的血小板减少症可能与GP Ib唾液酸含量减少有关。据我们所知，此前尚未描述过类似病例。
