Damage of pathogens

Question 1

ID50

Answer 1

Infectious dose 50
 50% of population
is infected by this amount

Question 2

LD50

Answer 2

Lethal dose 50

Toxin amount lethal to 50% of those infected

Question 3

What adaptions allow antigens to evade the immune system?

Answer 3

• Capsules
• Cell wall components
• Exo-Enzymes
• Antigenic variation

Question 4

Capsules

Answer 4

• Capsules have a thick protein layer
• May prevent/delay phagocytosis
• Presence often means high virulence
• Immune system will eventually produce antibodies to counter capsules

Question 5

Components of cell wall

Answer 5

• M protein resists phagocytosis
• Opa protein inhibits T helper cells
• Mycolic acid (waxy lipid) resists digestion

Question 6

Exo-Enzymes

Answer 6

Slow or stop some part of immune defense

• Coagulases  Cause blood clotting – wall off infection
• Hyaluronidase  Digests Hyaluronic acid – connective tissue  Increases spread of pathogen
• Collagenase  Digest collagen, similar to above
• IgA Proteases  Digest IgA - slows immune activation

Question 7

Antigenic variation

Answer 7

Immune system recognizes antigens – portions of proteins on cell surface.
Many pathogen can alter/change antigens over time