| Popis: |
Background. 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. Methods. Goat anti-rabbit alloantibodies were pepsin-digested and labeled with 125 I, 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. Results. Binding of radiolabeled F(ab') 2 fragments to rabbit cornea cells reached a maximum at 12 hr. At 32°C (rabbit corneal temperature), the radiolabel eluted rapidly from the cornea, reaching baseline at 72 hr. At 4°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. Conclusion. 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. |
