Jepsen H H, Teisner B, Rasmussen J M, Svehag S E
Institute of Medical Microbiology, Odense University, Denmark.
Scand J Immunol. 1989 Feb;29(2):247-55. doi: 10.1111/j.1365-3083.1989.tb01122.x.
Erythrocytes (E) from three factor I-deficient patients were investigated for surface-bound complement factors and CR1 (CD 35) expression and function. The E were coated with C4b, C3b, and factor H. Following plasma infusion or in vitro incubation of the patients' E with normal human serum (NHS) or purified factor I, cell-bound C4b and C3b could no longer be detected. The E now expressed C3d, and factor H was unaffected, indicating that factor H was bound to the C3d part of the C3b molecules, providing the co-factor for effective cleavage of E-bound C3b when purified factor I was added. The binding of monoclonal anti-CR1 antibodies (M710) to the patients' E was markedly reduced compared with control E, and was not normalized by treatment with NHS, probably because covalently bound C3d/factor H interfered with the binding of M710. By contrast, the reduced ability of the patients' E-CR1 to bind complement-opsonized immune complexes (IC) was normalized after plasma infusion. This shows that the impaired CR1 function was acquired and emphasizes the importance of performing functional CR1 assays. Complement opsonization of IC for binding to normal E was severely compromised in the patients' sera due to consumption of factor B and C3. After plasma infusion the opsonization capacity of the patients' sera was restored. Thus, two mechanisms of importance for normal clearance of IC were compromised in factor I-deficient patients: (1) the opsonization of IC for binding to E-CR1, and (2) the capacity of E-CR1 to bind opsonized complexes. Both dysfunctions were temporarily corrected by plasma infusion.
对三名I因子缺乏患者的红细胞（E）进行了表面结合补体因子以及CR1（CD 35）表达和功能的研究。这些红细胞包被有C4b、C3b和H因子。在输入血浆后，或将患者的红细胞与正常人血清（NHS）或纯化的I因子进行体外孵育后，细胞结合的C4b和C3b不再能被检测到。此时红细胞表达C3d，而H因子未受影响，这表明H因子与C3b分子的C3d部分结合，在加入纯化的I因子时为有效裂解结合在红细胞上的C3b提供了辅因子。与对照红细胞相比, 单克隆抗CR1抗体（M710）与患者红细胞的结合显著减少，并且用NHS处理后未恢复正常，这可能是因为共价结合的C3d/H因子干扰了M710的结合。相比之下，患者红细胞CR1结合补体调理的免疫复合物（IC）的能力降低在输入血浆后恢复正常。这表明受损的CR1功能是后天获得的，并强调了进行CR1功能检测的重要性。由于B因子和C3的消耗，患者血清中IC与正常红细胞结合的补体调理作用严重受损。输入血浆后，患者血清的调理能力得以恢复。因此，I因子缺乏患者中正常清除IC的两个重要机制受到损害：（1）IC与红细胞CR1结合的调理作用，以及（2）红细胞CR1结合调理复合物的能力。两种功能障碍都通过输入血浆得到了暂时纠正。
