Module 9 3.Patho: Describe the three mechanisms pathogens use to block the immune system. (hint Power-Kean: Table 8.3 is a nice review)

Question 1

What is one mechanism pathogens use to resist the immune system, and what is its effect on immunity?

Answer 1

• Mechanism: Production of toxins to kill phagocytes or interfere with chemotaxis.
  • Effect: Impairs the immune system’s ability to combat infection.
  • Example Microorganisms: Staphylococcus, Streptococcus, Mycobacterium tuberculosis.

Question 2

. How do some pathogens prevent phagocytosis, and which microorganisms employ this mechanism?

Answer 2

• Mechanism: Inhibition of phagocytosis by preventing fusion between phagosome and lysosomal granules.
  • Example Microorganisms: Staphylococcus, Salmonella typhi, Neisseria gonorrhoeae, Haemophilus influenzae, Streptococcus pneumoniae.

Question 3

What do pathogens produce to prevent killing by oxygen-dependent mechanisms, and which microorganisms use this strategy?

Answer 3

• Mechanism: Production of antioxidants (e.g., catalase, superoxide dismutase).
  • Example Microorganisms: Mycobacterium species, Salmonella typhi, Neisseria gonorrhoeae, Haemophilus influenzae, Streptococcus pneumoniae.

Question 4

How do some microorganisms interfere with the complement system and antibody opsonization, and which pathogens employ this mechanism?

Answer 4

• Mechanism: Production of surface molecules that mimic crystallizable fragment (Fc) receptors and bind antibodies.
  • Example Microorganisms: Staphylococcus, Herpes simplex virus.

Question 5

What is the mechanism used by pathogens to mimic self-antigens, and what is the potential consequence?

Answer 5

• Mechanism: Production of surface antigens similar to self-antigens.
  • Consequence: This resemblance may lead to the formation of antibodies against self-antigens, causing hypersensitivity diseases.
  • Example Microorganisms: Group A Streptococcus (M protein), Mycoplasma pneumoniae (red cell antigens).

Question 6

How do some pathogens change their antigenic profile, and what is the impact on the immune response?

Answer 6

• Mechanism: Undergo mutation of antigens or activate genes that change surface molecules.
  • Impact: Delays the immune response because the immune system fails to recognize the new antigen.
  • Example Microorganisms: Influenza, HIV, some parasites.