Morgan B P, Imagawa D K, Dankert J R, Ramm L E
J Immunol. 1986 May 1;136(9):3402-6.
Previous studies have demonstrated that in general, nucleated cells are more resistant to killing by serum complement than are erythrocytes. During studies aimed at defining the mechanisms of nucleated cell resistance, we found that the human histiocytic cell line U937 was easily lysed by homologous serum. U937 cells were also killed by serum depleted of C9, but not by serum depleted of C8, implying that the C5b-8 complex was sufficient to cause lysis of these cells. Enumeration of complexes on the cell surface demonstrated that approximately 40-fold more complexes were required to lyse U937 cells in the absence of C9 than in the presence of an excess of C9. Examination of the effects of small amounts of C9 on lysis of U937 cells by the C5b-8 complex demonstrated that at very low doses, C9 inhibited C5b-8 mediated lysis. The use of radiolabeled anti-C8 antibody showed that C5b-8 complexes were eliminated from the surface of U937 cells at 37 degrees C, and C9 at the dose causing inhibition of lysis accelerated the elimination of complexes. These results suggest that the increased lytic potential resulting from binding of small amounts of C9 to C5b-8 complexes is outweighed by enhanced elimination of complexes resulting in decreased cell death.
先前的研究表明，一般来说，有核细胞比红细胞更能抵抗血清补体的杀伤作用。在旨在确定有核细胞抗性机制的研究过程中，我们发现人类组织细胞系U937很容易被同源血清溶解。U937细胞也会被缺乏C9的血清杀死，但不会被缺乏C8的血清杀死，这意味着C5b - 8复合物足以导致这些细胞溶解。对细胞表面复合物的计数表明，在缺乏C9的情况下，溶解U937细胞所需的复合物数量大约是存在过量C9时的40倍。研究少量C9对C5b - 8复合物溶解U937细胞的影响表明，在非常低的剂量下，C9会抑制C5b - 8介导的溶解。使用放射性标记的抗C8抗体表明，C5b - 8复合物在37℃时从U937细胞表面消除，而导致溶解抑制的剂量的C9加速了复合物的消除。这些结果表明，少量C9与C5b - 8复合物结合所产生的增加的溶解潜力，被复合物消除增强导致的细胞死亡减少所抵消。
