Blake K M, Carrigan S O, Issekutz A C, Stadnyk A W
Department of Microbiology and Immunology, Dalhousie University and the Dalhousie Inflammation Group, Halifax, Nova Scotia, Canada.
Clin Exp Immunol. 2004 May;136(2):262-8. doi: 10.1111/j.1365-2249.2004.02429.x.
Recruitment of polymorphonuclear leucocytes (PMN) across the intestinal epithelium is dependent on specific adhesion molecules and chemoattractants diffusing from the intestinal lumen. The present understanding is that in response to fMLP, PMN migration across a T84 colon carcinoma monolayer is dependent on the beta(2) integrin, Mac-1 (CD11b/CD18). To further understand PMN transepithelial migration, we sought to determine whether migration to C5a, IL-8 and LTB(4) was similarly Mac-1-, or even CD18-dependent. T84 epithelial cell monolayers growing on Transwell filters were used in combination with radiolabelled peripheral blood PMN. The number of migrated PMN was established by the amount of radioactivity recovered from the well after the migration period. Monoclonal antibodies were used to block integrin function. Whereas essentially all migration to fMLP across T84 monolayers was prevented by anti-CD18 antibody, significant migration to C5a, IL-8 or LTB(4) persisted despite anti-CD18 antibody, indicating PMN are capable of beta(2) integrin-independent transepithelial migration. An antibody to CD11b but not CD11a blocked migration to an extent similar as with anti-CD18. CD18-independent PMN migration to C5a occurred only in the basolateral-to-apical direction across epithelial cells. Co-stimulation of PMN with C5a and fMLP or IL-8 plus LTB(4) and fMLP still resulted in CD18-independent migration. Thus CD18 use during PMN migration across this model epithelium is a function of the chemoattractant inducing migration. The finding of CD18-independent migration mechanisms needs to be considered when developing antiadhesion molecule strategies to reduce or reverse intestinal inflammation.
多形核白细胞（PMN）穿越肠上皮的过程依赖于特定的黏附分子以及从肠腔扩散而来的趋化因子。目前的认识是，在fMLP的刺激下，PMN穿越T84结肠癌细胞单层的迁移依赖于β(2)整合素Mac-1（CD11b/CD18）。为了进一步了解PMN的跨上皮迁移，我们试图确定向C5a、IL-8和LTB(4)的迁移是否同样依赖于Mac-1，甚至是否依赖于CD18。将生长在Transwell滤器上的T84上皮细胞单层与放射性标记的外周血PMN联合使用。迁移期结束后，通过从孔中回收的放射性活度来确定迁移的PMN数量。使用单克隆抗体来阻断整合素功能。尽管抗CD18抗体基本上阻止了所有PMN穿越T84单层向fMLP的迁移，但在抗CD18抗体存在的情况下，向C5a、IL-8或LTB(4)的显著迁移仍然存在，这表明PMN能够进行不依赖于β(2)整合素的跨上皮迁移。一种针对CD11b而非CD11a的抗体在一定程度上阻断迁移，其程度与抗CD18抗体相似。不依赖于CD18的PMN向C5a的迁移仅发生在上皮细胞从基底外侧到顶端的方向。用C5a和fMLP或IL-8加LTB(4)和fMLP共同刺激PMN仍然导致不依赖于CD18的迁移。因此，PMN在穿越该模型上皮迁移过程中对CD18的利用是诱导迁移的趋化因子的一个功能。在开发抗黏附分子策略以减轻或逆转肠道炎症时，需要考虑不依赖于CD18的迁移机制这一发现。
