Immune Evasion Strategies Flashcards
What are two possibilities when bacteria invade the immune system?
1) If, the immune system effectively recognize, and destroys all of the organisms that are present in any given infection, then that organism has failed to establish itself in the body, and thus cannot manifest in disease.
2) If, the immune system does fail in its task, often the reason for this failure is that the invading organism has evolved a strategy for evading or suppressing the hosts immune response to that organism.
What are seven strategies for bacteria to evade the immune system?
1) Strategies directed against acquired immunity.
2) Strategies directed against phagocytes.
3) Suppression of antibodies - hiding inside cells.
4) Anti-oxidant enzymes.
5) Forming spores.
6) Developing special adherence mechanisms.
7) Production of toxins and causing tissue damage.
How do bacteria suppress antibodies?
Here, the invading organism targets those cells of the immune system that specifically react against them. The organism prevents the body from mounting an immune response against it.
What bacteria species suppress antibodies?
Mycobacterium tuberculosis, the cause of the disease tuberculosis.
What substance does Mycobacterium tuberculosis reduce?
Interleukin-2.
How do bacteria hide inside cells?
The cells of the immune system with bacteria inside them do not present antigens that will evoke an immune response. They multiply inside these cells, and then further invade the body when they are greater in number.
What three bacteria hide inside cells?
1) Brucella.
2) Listeria.
3) Mycobacterium tuberculosis.
What cell do these three bacteria infect?
Macrophages.
What are two examples of bacteria that can escape the vacuole to access the cytoplasm?
1) Shigella.
2) Listeria.
What is the enzyme some bacteria have that negates superoxide produced by granulocytes?
Superoxide dismutase.
Which bacteria’s spores have been known to reinfect animals over 70 years after burial sites were disturbed?
Bacillus anthraces.
What is the major finding in the bodies of animals that have anthrax?
An enlarged spleen.
What are major clinical signs of anthrax?
1) Septicemia.
2) Respiratory distress.
3) Drooling.
4) Stupor.
5) Convulsions.
6) Collapse.
What are the two things that cause death in anthrax cases?
1) Asphyxiation.
2) Organ collapse.
What are the two toxins produced by bacteria that cause tissue damage?
1) Exotoxins.
2) Endotoxins.
What is an exotoxin?
An exotoxin is a toxin excreted by a microorganism.
How does an exotoxin cause damage to the host?
By destroying cells or disrupting normal metabolism. They are highly potent and can cause major damage to the host.
What are two well known exotoxins?
1) Botulinum toxin produced by Clostridium botulinum.
2) Corynebacterium diphtheriae exotoxin.
What bacterial organisms typically use exotoxins?
Cocci bacteria.
What are endotoxins?
They are part of the outer membrane of the cell wall of Gram-negative bacteria.
What do endotoxins do?
They trigger phagocytes to release cytokines that produce local or systemic symptoms.
What organisms usually have endotoxins?
Bacterial species ending in “-ella”.
What are three common symptoms caused by endotoxins?
1) Fever.
2) Shock.
3) Leukopenia.
What are four strategies directed against phagocytes?
1) Inhibit chemotaxis.
2) Inhibition of phagocytosis.
3) Killing the phagocyte.
4) Colonization of the phagocyte.
