Gebhardt B M, Varnell E D, Kaufman H E
Lions Eye Research Laboratories, LSU Eye Center, Louisiana State University Medical Center School of Medicine, New Orleans 70112-2234, USA.
Transplantation. 1999 Feb 27;67(4):594-9. doi: 10.1097/00007890-199902270-00018.
In this study, we determined the binding characteristics of F(ab')2 alloantibody fragments to corneal antigens and assessed the capacity of these antibody fragments to protect corneal allografts from immune attack.
Goat anti-rabbit alloantibodies were pepsin-digested and labeled with 125I, and the time course of association and dissociation of the F(ab')2 fragments was determined. Corneal allografts were incubated in unlabeled F(ab')2 fragments and transplanted into allogeneic recipients, and the graft survival times were recorded.
Binding of radiolabeled F(ab')2 fragments to rabbit cornea cells reached a maximum at 12 hr. At 32 degrees C (rabbit corneal temperature), the radiolabel eluted rapidly from the cornea, reaching baseline at 72 hr. At 4 degrees C (corneal graft storage temperature), significant amounts remained associated with the cornea at 96 hr. Mean survival time for grafts incubated in F(ab')2 anti-rabbit fragments was significantly greater than that of grafts incubated in nonimmune F(ab')2 fragments. Three of the corneal allografts incubated in goat F(ab')2 anti-rabbit fragments survived for 100 days, whereas the longest surviving control allograft incubated in goat F(ab')2 nonimmune fragments was rejected on day 24. Preincubation of corneas in unlabeled, immune F(ab')2 fragments followed by incubation in radiolabeled, immune F(ab')2 fragments suggested that antigen masking was not a factor in the prolongation of graft survival.
Based on the binding and release kinetics and the graft survival times, it appears that the protective effect of immune F(ab')2 fragments extends well beyond the binding interval of the antibody fragments to corneal cell membranes.
在本研究中，我们确定了F(ab')2同种异体抗体片段与角膜抗原的结合特性，并评估了这些抗体片段保护角膜同种异体移植物免受免疫攻击的能力。
用胃蛋白酶消化山羊抗兔同种异体抗体并用125I标记，测定F(ab')2片段的结合和解离时间进程。将角膜同种异体移植物在未标记的F(ab')2片段中孵育，然后移植到同种异体受体中，记录移植物存活时间。
放射性标记的F(ab')2片段与兔角膜细胞的结合在12小时达到最大值。在32℃（兔角膜温度）时，放射性标记物迅速从角膜洗脱，在72小时达到基线。在4℃（角膜移植物储存温度）时，96小时仍有大量与角膜结合。在F(ab')2抗兔片段中孵育的移植物的平均存活时间显著长于在非免疫F(ab')2片段中孵育的移植物。在山羊F(ab')2抗兔片段中孵育的3个角膜同种异体移植物存活了100天，而在山羊F(ab')2非免疫片段中孵育的存活时间最长的对照同种异体移植物在第24天被排斥。角膜在未标记的免疫F(ab')2片段中预孵育，然后在放射性标记的免疫F(ab')2片段中孵育，这表明抗原掩盖不是移植物存活延长的因素。
根据结合和释放动力学以及移植物存活时间，免疫F(ab')2片段的保护作用似乎远远超出抗体片段与角膜细胞膜的结合间隔。
