Vedeler C A, Matre R, Iversen B M
Broegelmann Research Laboratory for Microbiology, Gade Institute, Norway.
Int Arch Allergy Appl Immunol. 1990;92(1):60-3. doi: 10.1159/000235225.
Adherence of sheep erythrocytes (E) sensitized with IgM antibodies (A) and C3b (EAC3b) to C3b/C4b receptors (CR1) in cryostat sections of human renal glomeruli was studied using the closed chamber technique. The adsorption was stable for at least 3 h at 37 degrees C. In the presence of purified factor I, the indicator cells, however, detached from the sections after 30 min at 37 degrees C. Factor H was not required. The release was not due to loss of CR1 activity in the tissue. The detached indicator cells were negative in the immune adherence test and were agglutinated by antibody to C3d, but not by antibody to C3c. Western blot of the detached indicator cells revealed the presence of C3d and C3c was found in the chamber fluid. Accordingly, detachment of the indicator cells was due to degradation of C3b to C3d with the release of C3c into the chamber fluid. Protease inhibitors did not prevent the detachment of the indicator cells. EAC3b incubated with sections of renal glomeruli preincubated with anti-CR1 antibody were not degraded. The results therefore indicate that CR1 in situ in renal glomeruli can provide the necessary cofactor activity for factor I-mediated degradation of C3b to C3d and C3c.
采用封闭腔室技术，研究了用IgM抗体（A）和C3b致敏的绵羊红细胞（E）（EAC3b）与人肾小球冷冻切片中C3b/C4b受体（CR1）的黏附情况。在37℃下，这种吸附至少3小时是稳定的。然而，在存在纯化的I因子的情况下，指示细胞在37℃下30分钟后从切片上脱离。不需要H因子。这种释放不是由于组织中CR1活性的丧失。脱离的指示细胞在免疫黏附试验中呈阴性，并且被抗C3d抗体凝集，但不被抗C3c抗体凝集。对脱离的指示细胞进行蛋白质印迹分析显示存在C3d，并且在腔室液中发现了C3c。因此，指示细胞的脱离是由于C3b降解为C3d，同时C3c释放到腔室液中。蛋白酶抑制剂不能阻止指示细胞的脱离。用抗CR1抗体预孵育的肾小球切片与EAC3b孵育后未发生降解。因此，结果表明肾小球原位的CR1可以为I因子介导的C3b降解为C3d和C3c提供必要的辅因子活性。
