Frank M M, Joiner K, Hammer C
Laboratory of Clinical Investigation, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland 20892.
Rev Infect Dis. 1987 Sep-Oct;9 Suppl 5:S537-45. doi: 10.1093/clinids/9.supplement_5.s537.
The factors controlling lysis of gram-negative bacteria by complement are being investigated systematically. The first question was how smooth Salmonella minnesota, which has on its surface lipopolysaccharide with long O polysaccharide side chains, avoids lysis. Rough organisms are serum sensitive. In both smooth and rough organisms, complement components are deposited on the surface and the lytic sequence proceeds to completion. However, with serum-resistant organisms the membrane attack complex (MAC), composed of late-acting complement proteins, does not successfully insert into the outer membrane to cause membrane damage. At the completion of the lytic sequence, the hydrophobic MAC is shed. C3b, which directs late component assembly, is deposited on the longest O polysaccharide side chains on these smooth organisms, where it does not direct successful insertion of the MAC into the outer membrane. Serum-resistant gonococci sequester the MAC on the organism's surface in association with specific outer membrane components, where it does no damage to the outer membrane. Antibody appears to mediate site-directed complement component deposition in a number of systems. Thus, depending on antibody specificity, complement may be deposited on the organism's surface to cause successful complement attack or may block complement attack induced by bactericidal antibody. Monoclonal antibodies of the same isotype directed at different epitopes on the same bacterial surface antigen may either induce lysis or block lytic attack.
正在系统研究补体对革兰氏阴性菌的裂解控制因素。第一个问题是，表面带有长O多糖侧链脂多糖的明尼苏达沙门氏菌是如何避免被裂解的。粗糙型菌株对血清敏感。在光滑型和粗糙型菌株中，补体成分都会沉积在表面，并且裂解过程会持续进行直至完成。然而，对于血清抗性菌株，由后期作用的补体蛋白组成的膜攻击复合物（MAC）无法成功插入外膜以造成膜损伤。在裂解序列完成时，疏水性MAC会脱落。指导后期成分组装的C3b沉积在这些光滑型菌株最长的O多糖侧链上，在此处它无法指导MAC成功插入外膜。血清抗性淋病奈瑟菌将MAC隔离在菌体表面并与特定外膜成分结合，在此处它不会对外膜造成损伤。在许多系统中，抗体似乎介导了补体成分的定点沉积。因此，根据抗体特异性，补体可能沉积在菌体表面导致成功的补体攻击，也可能阻断杀菌抗体诱导的补体攻击。针对同一细菌表面抗原上不同表位的同型单克隆抗体可能会诱导裂解或阻断裂解攻击。
