Etzioni A, Tonetti M
Department of Pediatrics, Rambam Medical Center, B. Rappaport School of Medicine, Technion, Haifa, Israel.
Immunol Rev. 2000 Dec;178:138-47. doi: 10.1034/j.1600-065x.2000.17805.x.
Leukocyte adhesion deficiency (LAD) type II is the second human disorder identified which involves the adhesion cascade. While in LAD I the integrin family is defective, in LAD II the selectin system is involved. The syndrome has been described in only five patients and is transmitted as an autosomal recessive trait. The infectious episodes and the severity are much milder than those observed in LAD I, and the only persistent clinical symptom is chronic severe periodontitis. Delay separation of the umbilical cord, which is a hallmark for LAD I, was not observed in any of the LAD II patients. The exact defect in the system is absence of the SLeX, which is an important ligand for the selectin on the leukocyte lead ing to a profound defect in leukocyte rolling, the first step in the adhesion cascade. This causes a marked decrease in chemotaxis accompanied by pronounced neutrophilia. Apart from the leukocyte defect, these patients suffer from severe growth and mental retardation and exhibit the rare Bombay blood group type. The primary defect in the syndrome is in fucose metabolism, with the absence of all fucosylated glycans on cell surface membranes. Recently, it is was found that the defect is in a specific transporter of GDP fucose into the Golgi apparatus, and thus no fucosylation process takes place, and no surface expression can be detected. The exact genetic defect in the transporter is still unknown. Four of the patients were of Arabic origin while the fifth was of Turkish origin. It seems that the primary defect is somewhat different and, therefore, fucose administration was effective in the Turkish child, but did not show any beneficial results in the patients of Arabic origin.
II型白细胞黏附缺陷症（LAD）是第二种被确认的涉及黏附级联反应的人类疾病。在I型LAD中，整合素家族存在缺陷，而在II型LAD中，选择素系统受累。该综合征仅在5例患者中被描述，呈常染色体隐性遗传。其感染发作及严重程度比I型LAD中观察到的要轻得多，唯一持续的临床症状是慢性严重牙周炎。I型LAD的标志性症状脐带延迟脱落，在任何II型LAD患者中均未观察到。该系统的确切缺陷是缺乏SLeX，SLeX是白细胞上选择素的重要配体，导致黏附级联反应的第一步白细胞滚动出现严重缺陷。这会导致趋化性显著降低并伴有明显的嗜中性粒细胞增多。除了白细胞缺陷外，这些患者还患有严重的生长和智力发育迟缓，并表现出罕见的孟买血型。该综合征的主要缺陷在于岩藻糖代谢，细胞表面膜上所有岩藻糖基化聚糖均缺失。最近发现，缺陷在于将GDP岩藻糖转运至高尔基体的特定转运蛋白，因此无法进行岩藻糖基化过程，也检测不到表面表达。转运蛋白的确切基因缺陷仍不清楚。其中4例患者来自阿拉伯，第5例来自土耳其。似乎主要缺陷有所不同，因此，给予岩藻糖对土耳其患儿有效，但对阿拉伯裔患者未显示出任何有益效果。
