《微生物学》课程PPT课件讲稿（英文版）Lecture 8 Microbial Interference with Host Defenses

Overall Strategies Defense against complement Subversion of phagocytosis Subversion of immune responses BIOL 533 Lecture 8

BIOL 533 2 Lecture 8 Overall Strategies • Defense against complement • Subversion of phagocytosis • Subversion of immune responses

General Aspects Pathogen finds itself in hostile territory Host fights back and usually--but not always--wins o Host's defenses are interrelated and so are organisms countermeasures BIOL 533 Lecture 8

BIOL 533 3 Lecture 8 General Aspects • Pathogen finds itself in hostile territory – Host fights back and usually—but not always—wins • Host’s defenses are interrelated and so are organism’s countermeasures

General Aspects Given organism sometimes has numerous different virulence factors Does not have to harm tissue to be called virulence factor, although many do Have to determine precise role of each factor if a large number are involved Not always sure in vitro situation is same as in disease state BIOL 533 Lecture 8

BIOL 533 4 Lecture 8 General Aspects – Given organism sometimes has numerous different virulence factors • Does not have to harm tissue to be called virulence factor, although many do • Have to determine precise role of each factor if a large number are involved – Not always sure in vitro situation is same as in disease state

E Defense Against Complement Overall strategies Inhibit complement activation Mask activating substances paul IgA antibodies Cover up target of complement membrane attack complex BIOL 533 Lecture 8

BIOL 533 5 Lecture 8 Defense Against Complement • Overall strategies – Inhibit complement activation • Mask activating substances – Capsule – IgA antibodies – Cover up target of complement membrane attack complex

E Defense Against Complement Overall strategies, continued Appropriate inhibitor to activation to surface Inactivate complement chemotaxin C5a BIOL 533 Lecture 8

BIOL 533 6 Lecture 8 Defense Against Complement • Overall strategies, continued – Appropriate inhibitor to activation to surface – Inactivate complement chemotaxin C5a

a Prevent Complement Activation "t Masking surface components that activate by the alternative pathway Capsules Murein of s, aureus good activator, but is covered by capsule Capsules rich in sialic acid of Group B streptococci and strains of e,co∥ BIOL 533 7 Lecture 8

BIOL 533 7 Lecture 8 Prevent Complement Activation • Masking surface components that activate by the alternative pathway – Capsules • Murein of S. aureus good activator, but is covered by capsule • Capsules rich in sialic acid of Group B streptococci and strains of E. coli

a Prevent Complement Activation "t IgA antibodies Meningococci get coated with IgA antibody Does not activate complement Prevents other ab that can activate from reaching surface of cell BIOL 533 Lecture 8

BIOL 533 8 Lecture 8 Prevent Complement Activation – IgA antibodies • Meningococci get coated with IgA antibody – Does not activate complement – Prevents other Ab that can activate from reaching surface of cell

a Prevent Complement Activation "t Cost of having capsule- antigenic Elicits activation by primary pathway Defend better against immediate defenses than later ones BIOL 533 Lecture 8

BIOL 533 9 Lecture 8 Prevent Complement Activation • Cost of having capsule— antigenic – Elicits activation by primary pathway • Defend better against immediate defenses than later ones

a Prevent Complement Activation "t Cover up target of membrane attack complex(outer membrane) Gram, such as salmone∥aorE,CO∥ Smooth strains with long 0 antigen polysaccharide chain do not allow access of mac while rough strains(with little or no 0 antigen)do Correlates with pathogenicity BIOL 533 Lecture 8

BIOL 533 10 Lecture 8 Prevent Complement Activation • Cover up target of membrane attack complex (outer membrane) – Gram—, such as Salmonella or E. coli • Smooth strains with long ‘0’ antigen polysaccharide chain do not allow access of mac while rough strains (with little or no ‘0’ antigen) do – Correlates with pathogenicity

Subversion of phagocytosis Overall str ategies Inhibition of phagocyte recruitment Microbial killing of phagocytes Escape of ingestion BIOL 533 Lecture 8

BIOL 533 11 Lecture 8 Subversion of Phagocytosis • Overall strategies – Inhibition of phagocyte recruitment – Microbial killing of phagocytes – Escape of ingestion