The Complement System CHAPTER 13 313 Killed FIGURE 13-11 Scanning electron micrographs of E coli showing Note membrane blebbing on lysed cells. From R. D. Schreiber et (a)intact cells and(b, c)cells killed by complement-mediated lysis. al, 1979, J Exp. Med. 149: 870.] inflammatory response. In addition to these mechanisms of Lysis of nucleated cells requires formation of multiple embrane attack complexes, whereas a single mac can lyse tain proteins that can interrupt the complement cascade on a red blood cell. Many nucleated cells, including the majority their surfaces, thus mimicking the effects of the normal com- of cancer cells, can endocytose the MAC. If the complex is plement regulatory proteins C4bBP, CRl, and dAF removed soon enough, the cell can repair any membrane TABLE 13-5 Microbial evasion of complement-mediated damage Microbial componen Mechanism of evasion Examples GRAM- NEGATIVE BACTERIA accharide chains chains prevent insertion of Resistant strains of e. coli and AC into bacterial membrane salmonella Outer membrane protein MAC interacts with membrane Resistant strains of neisseria protein and fails to insert into gonorrhoeae bacterial membrane Elastase Anaphylatoxins C3a and C5a are Pseudomonas aeruginosa inactivated by microbial elastase GRAM- POSITIVE BACTERIA Peptidoglycan layer of cell wall layer of peptidoglycan Bacterial capsule Capsule provides physical barrier bacterial membrane and crt on phagocytic cells OTHER MICROBES Proteins that mimic complemen Protein present in various bacteria Vaccinia virus, herpes simplex regulatory proteins viruses, fungi, and protozoans pstein-Barr virus, Trypanosoma inhibit the complement cascade cruzi candida albicans KEY: CR1 type 1 complement receptor; LPS=lipopolysaccharide; MAC membrane-attack complex(C5b-9)inflammatory response. In addition to these mechanisms of evasion, various bacteria, viruses, fungi, and protozoans con￾tain proteins that can interrupt the complement cascade on their surfaces, thus mimicking the effects of the normal com￾plement regulatory proteins C4bBP, CR1, and DAF. Lysis of nucleated cells requires formation of multiple membrane attack complexes, whereas a single MAC can lyse a red blood cell. Many nucleated cells, including the majority of cancer cells, can endocytose the MAC. If the complex is removed soon enough, the cell can repair any membrane The Complement System CHAPTER 13 313 (a) Alive FIGURE 13-11 Scanning electron micrographs of E. coli showing (a) intact cells and (b, c) cells killed by complement-mediated lysis. Note membrane blebbing on lysed cells. [From R. D. Schreiber et al., 1979, J. Exp. Med. 149:870.] (b) Killed (c) Killed TABLE 13-5 Microbial evasion of complement-mediated damage Microbial component Mechanism of evasion Examples GRAM-NEGATIVE BACTERIA Long polysaccharide chains Side chains prevent insertion of Resistant strains of E. coli and in cell-wall LPS MAC into bacterial membrane Salmonella Outer membrane protein MAC interacts with membrane Resistant strains of Neisseria protein and fails to insert into gonorrhoeae bacterial membrane Elastase Anaphylatoxins C3a and C5a are Pseudomonas aeruginosa inactivated by microbial elastase GRAM-POSITIVE BACTERIA Peptidoglycan layer of cell wall Insertion of MAC into bacterial Streptococcus membrane is prevented by thick layer of peptidoglycan Bacterial capsule Capsule provides physical barrier Streptococcus pneumoniae between C3b deposited on bacterial membrane and CR1 on phagocytic cells OTHER MICROBES Proteins that mimic complement Protein present in various bacteria, Vaccinia virus, herpes simplex, regulatory proteins viruses, fungi, and protozoans Epstein-Barr virus, Trypanosoma inhibit the complement cascade cruzi, Candida albicans KEY: CR1  type 1 complement receptor; LPS  lipopolysaccharide; MAC  membrane-attack complex (C5b–9)