Okada Y, Kannagi R, Levery S B, Hakomori S
J Immunol. 1984 Aug;133(2):835-42.
Neutral glycolipids and gangliosides of umbilical cord and adult human erythrocytes were separated by high performance liquid chromatography, and each fraction was analyzed by direct binding of anti-I (Ma) and anti-i (Den) on solid phase glycolipid-lecithin-cholesterol. The I- and i-active glycolipids were isolated and their structures were determined by methylation analysis and direct probe mass spectrometry. The major I antigen in adult erythrocytes, showing a remarkable binding activity with anti-I(Ma), was found in one neutral glycolipid fraction, designated fraction y4, which was identified as a mixture of two glycolipids of a new type, lactoisooctaosylceramide and monofucosyllactoisooctaosylceramide (for structures, see Table I). In addition, two gangliosides displaying direct binding activity with anti-I(Ma) were identified as monosialoganglioside G8, as previously described and disialosyllactoisooctaosylceramide, which showed the same level of I activity as the y4 glycolipid. The same ganglioside was recently isolated and characterized by Kundu and co-workers. The major i-active glycolipid antigen in umbilical cord erythrocytes, showing a strong binding activity with anti-i(Den), was a neutral glycolipid, x4a, which was identified as lactonorhexaosylceramide. This glycolipid without fucosyl or sialosyl substitution has not been isolated previously and was present as an obvious normal component of umbilical cord erythrocytes, but an extremely minor component of adult erythrocytes. Sialosyllactonorhexaosylceramide (G6) was isolated and characterized as a second i antigen of umbilical cord erythrocytes, but showed a very weak binding activity with the anti-i antibody. Although these sialosyl derivatives displayed only weak activity, the chemical quantity of the sialosyl derivatives is significantly large in fetal erythrocytes; therefore, Ii activity of human erythrocytes, in general, must be significantly dependent on sialosyl derivatives in addition to unsubstituted structures.
采用高效液相色谱法分离脐带血和成人红细胞中的中性糖脂和神经节苷脂，通过抗-I（Ma）和抗-i（Den）在固相糖脂-卵磷脂-胆固醇上的直接结合对每个组分进行分析。分离出具有I活性和i活性的糖脂，并通过甲基化分析和直接探针质谱法确定其结构。在一个中性糖脂组分（命名为y4组分）中发现了成人红细胞中的主要I抗原，该组分与抗-I（Ma）具有显著的结合活性，经鉴定为一种新型的两种糖脂的混合物，即乳糖异辛糖基神经酰胺和单岩藻糖基乳糖异辛糖基神经酰胺（结构见表I）。此外，两种与抗-I（Ma）具有直接结合活性的神经节苷脂被鉴定为单唾液酸神经节苷脂G8（如前所述）和二唾液酸乳糖异辛糖基神经酰胺，其I活性水平与y4糖脂相同。最近，Kundu及其同事分离并鉴定了相同的神经节苷脂。脐带血红细胞中主要的i活性糖脂抗原与抗-i（Den）具有强烈的结合活性，是一种中性糖脂x4a，经鉴定为乳糖新己糖基神经酰胺。这种没有岩藻糖基或唾液酸基取代的糖脂以前尚未分离出来，是脐带血红细胞的一种明显正常成分，但在成人红细胞中是一种极其微量的成分。唾液酸乳糖新己糖基神经酰胺（G6）被分离并鉴定为脐带血红细胞的第二种i抗原，但与抗-i抗体的结合活性非常弱。尽管这些唾液酸基衍生物仅表现出较弱的活性，但在胎儿红细胞中唾液酸基衍生物的化学量显著较大；因此，一般来说，人类红细胞的Ii活性除了依赖于未取代的结构外，还必须显著依赖于唾液酸基衍生物。
