Moore Sam W, Sidler Daniel, Zaahl Monique G
Division of Paediatric Surgery, Faculty of Health Sciences, University of Stellenbosch, PO Box 19063, 7505 Tygerberg, South Africa.
J Pediatr Surg. 2008 Aug;43(8):1439-44. doi: 10.1016/j.jpedsurg.2007.12.057.
Hirschsprung's disease (HSCR)-associated enterocolitis (HAEC) remains a major contributor to morbidity and mortality associated with HSCR, being sometimes difficult to diagnose in its subclinical form. Its pathogenesis appears to include impaired local defense mechanisms as well as dysfunctional immune response and leukocyte function. In this context, the ITGB2 (CD18) immunomodulation-related gene is a possible candidate in HAEC pathogenesis as it codes for the beta-subunit of leukocyte adhesion molecule lymphocyte function-associated antigen 1, which has an established role in T-cell development and function. ITGB2/CD18 has also been linked to chronic colitis in both human and animal models involving defense mechanisms within colonic mucosa. There is therefore a fairly compelling case for the potential involvement of the ITGB2 (CD18) in HAEC pathogenesis.
The aim of this study was to investigate the ITGB2 immunomodulatory gene (CD18) in a cohort of patients with HSCR and explore its correlation with enterocolitis.
Screening for mutations of the ITGB2 (CD18) gene was performed on DNA extracted from colonic tissue samples and whole blood of 33 HSCR patients controlled by analysis of 60 unaffected individuals from the diverse South African population. Polymerase chain reaction amplification was performed, followed by heteroduplex single-strand conformation polymorphism analysis and bidirectional semiautomated DNA sequencing analysis.
Heteroduplex single-strand conformation polymorphism banding patterns of the ITGB2 gene showed variations in 22 HSCR patients (66%), 13 of whom had severe episodes of HAEC, and 6 others had milder symptoms. Of the 13, 6 (46%) had Down's syndrome-associated HSCR. Genetic variations included 1 mutation (D77N), 2 known (V367, V441), and 4 novel polymorphisms (-111T/C, 24G/T, 295G/A, 892A/G). Significant associations were identified in the exon 5' untranslated promotor region (P < .0001), exon 10 (P < .0007), and the 3' untranslated promotor region at 122G/A (P < .0001) and 370 G/T positions (P = .04). Those regions of the gene most frequently associated with HAEC and severe symptoms were those with more than 1 variant identified in the gene.
This study shows that impaired CD18 leukocyte and T regulatory cell regulation can probably be linked to a genetic (ITGB2) predisposition to HAEC. It furthermore provides a possible genetic link to HAEC patient selection, identifying a potential molecular target.
先天性巨结肠病（HSCR）相关的小肠结肠炎（HAEC）仍然是与HSCR相关的发病和死亡的主要原因，其亚临床形式有时难以诊断。其发病机制似乎包括局部防御机制受损以及免疫反应和白细胞功能失调。在这种情况下，ITGB2（CD18）免疫调节相关基因可能是HAEC发病机制中的一个候选基因，因为它编码白细胞粘附分子淋巴细胞功能相关抗原1的β亚基，该亚基在T细胞发育和功能中具有既定作用。在涉及结肠黏膜防御机制的人类和动物模型中，ITGB2/CD18也与慢性结肠炎有关。因此，有相当有说服力的理由认为ITGB2（CD18）可能参与HAEC的发病机制。
本研究的目的是调查一组HSCR患者中的ITGB2免疫调节基因（CD18），并探讨其与小肠结肠炎的相关性。
对33例HSCR患者的结肠组织样本和全血中提取的DNA进行ITGB2（CD18）基因突变筛查，并通过分析来自不同南非人群的60名未受影响个体进行对照。进行聚合酶链反应扩增，随后进行异源双链单链构象多态性分析和双向半自动DNA测序分析。
ITGB2基因的异源双链单链构象多态性条带模式在22例HSCR患者（66%）中显示出变异，其中13例有严重的HAEC发作，另外6例症状较轻。在这13例中，6例（46%）患有唐氏综合征相关的HSCR。基因变异包括1个突变（D77N）、2个已知变异（V367、V441）和4个新的多态性（-111T/C、24G/T、295G/A、892A/G）。在外显子5'非翻译启动子区域（P <.0001）、外显子10（P <.0007）以及3'非翻译启动子区域的122G/A（P <.0001）和370 G/T位置（P =.04）发现了显著关联。该基因中最常与HAEC和严重症状相关的区域是那些在基因中鉴定出不止1个变异的区域。
本研究表明，CD18白细胞和T调节细胞调节受损可能与HAEC的遗传（ITGB2）易感性有关。此外，它为HAEC患者的选择提供了可能的遗传联系，确定了一个潜在的分子靶点。
