Xu Heping, Manivannan Ayyakkannu, Liversidge Janet, Sharp Peter F, Forrester John V, Crane Isabel J
Department of Ophthalmology, Aberdeen University Medical School, Scotland, United Kingdom.
J Leukoc Biol. 2002 Dec;72(6):1133-41.
In the present study, we investigated the involvement of CD44 in leukocyte trafficking in vivo at the blood-retinal barrier using experimental autoimmune uveoretinitis (EAU) as a model system. Leukocyte trafficking was evaluated using adoptive transfer of calcein-AM (C-AM)-labeled spleen cells harvested from syngeneic mice at prepeak severity of EAU to mice at a similar stage of disease. CD44 and its ligand hyaluronan were up-regulated in the eye during EAU. CD44-positive leukocytes were found sticking in the retinal venules and postcapillary venules but not in the retinal arterioles nor in mesenteric vessels. Preincubation of in vitro C-AM-labeled leukocytes with anti-CD44 monoclonal antibodies (mAb; IM7) or high molecular weight hyaluronic acid (HA) before transfer significantly suppressed leukocyte rolling but not sticking in retinal venules and also reduced cell infiltration in the retinal parenchyma. Administration of the HA-specific enzyme hyaluronidase to mice before cell transfer also reduced leukocyte infiltration, suggesting that CD44-HA interactions are involved in leukocyte recruitment in EAU. This was further supported by the observation that disease severity was reduced by administration of anti-CD44 mAb (IM7) at the early leukocyte-infiltration stage. Further studies also indicated that CD44 activation was associated with increased levels of apoptosis, and this may also be in part responsible for the reduction in disease severity. These findings demonstrate that CD44 is directly involved in leukocyte-endothelial interaction in vivo and influence the trafficking of primed leukocytes to the retina and their overall survival.
在本研究中，我们以实验性自身免疫性葡萄膜视网膜炎（EAU）作为模型系统，研究了CD44在血视网膜屏障处白细胞体内运输中的作用。通过将从处于EAU严重程度高峰前期的同基因小鼠采集的钙黄绿素-AM（C-AM）标记的脾细胞过继转移到处于相似疾病阶段的小鼠体内，来评估白细胞运输情况。在EAU期间，眼睛中CD44及其配体透明质酸上调。发现CD44阳性白细胞黏附于视网膜小静脉和毛细血管后小静脉，但不在视网膜小动脉和肠系膜血管中。在转移前，将体外C-AM标记的白细胞与抗CD44单克隆抗体（mAb；IM7）或高分子量透明质酸（HA）预孵育，可显著抑制白细胞在视网膜小静脉中的滚动，但不影响其黏附，并且还减少了视网膜实质中的细胞浸润。在细胞转移前给小鼠注射HA特异性酶透明质酸酶也可减少白细胞浸润，这表明CD44-HA相互作用参与了EAU中的白细胞募集。在白细胞浸润早期给予抗CD44 mAb（IM7）可减轻疾病严重程度，这一观察结果进一步支持了这一点。进一步的研究还表明，CD44激活与凋亡水平升高有关，这也可能部分导致了疾病严重程度的降低。这些发现表明，CD44直接参与体内白细胞与内皮细胞的相互作用，并影响致敏白细胞向视网膜的运输及其总体存活。
