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Evolutionary Medicine > Quiz 4 (lecture 14) > Flashcards

Quiz 4 (lecture 14) Flashcards

1
Q

What are the 3 defensive strategies used to deal with many hostile environmental factors, not just infections?

A

avoidance, resistance, and tolerance
- whenever possible all are used (if cannot be used then remaining will be main defenses)

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2
Q

When are avoidance behaviors used?

A
  • to reduce pathogen exposure
  • include innate and acquired aversion of markers of high microbial density (smell, taste)
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3
Q

Avoidance is a normal defensive response, but people vary in what?

A

significantly in expression
- ex. extreme response is germophobia (a common form of OCD)

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4
Q

What do tolerance mechanisms do?

A
  • reduce the negative effects on host fitness of a given level of pathogen burden
  • they protect and repair tissues
  • we all tolerate chronic viral infections
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5
Q

Do tolerance mechanisms affect pathogens directly?

A

No, they impose less selection on pathogens than do resistance mechanisms

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6
Q

What is the evolutionary consequence of tolerance mechanisms?

A

there is less of an “arms race” and little variation among individuals for tolerance genes

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7
Q

T/F Most of us are chronically infected by some virus and tolerate it.

A

true

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8
Q

If you are infected, then what are your choices and why do you make that choices?

A
  • the choice is to tolerate or resist
  • make that decision based on the benefits and cost of resistance (varies among tissues and organs)
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9
Q

typically but not universally, the rule of defense

A

if possible, avoid; if cannot avoid, resist; if cannot resist, tolerate

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10
Q

What is the aim of resistance mechanisms?

A
  • to eliminate the infection once it is established
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11
Q

What system’s main function is resistance?

A
  • the immune system
    – reduce pathogen burden through detection, destruction, and elimination
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12
Q

what is the major cost of resistance?

A

immunopathology

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13
Q

resistance definition

A

host use inflammation to reduce infection intensity until the cost of the immune response is larger than the cost of infection in the absence of inflammation

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14
Q

what is the function of the immune system?

A

to protect the organism against pathogens

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15
Q

what are the problems of the immune system?

A
  • pathogens can re-infect
  • pathogens evolve
  • pathogens are made from the same stuff that we are
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16
Q

what are solutions of the immune system?

A
  • a memory of past infections
  • respond flexibly to pathogens w/ characteristics never seen before
  • figure out how to recognize self and not destroy it
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17
Q

Which animals have innate immune systems?

A

found in all animals

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18
Q

What are the five features of the innate immune system?

A
  1. Epithelial barriers (mucosa and skin)
  2. Phagocytes and their antimicrobial defenses (lysozymes)
  3. Complement system (coat, smother, and attach to pathogens)
  4. Anti-viral defenses (NK cells and interferons)
  5. Anti-parasitic defenses
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19
Q

What does the innate immune system rely on?

A

pattern recognition receptors to sense microbial infections

20
Q

What do the pattern recognition receptors sense?

A

detect conserved structures that are unique to microorganisms

21
Q

The innate immune system leads to the activation of what? (just in vertebrates)

A

adaptive immunity

22
Q

What is the key feature of the adaptive immune system?

A

The generation of antigen receptors by somatic recombination

23
Q

What does the adaptive immune systems’ output?

A

highly diverse repertoire of antigen receptors (antibodies and t cell receptors)

24
Q

Antigen receptors can detect?

A

any antigen
(self, microbial non-self, or non-microbial non-self)

25
Q

What is an antigen?

A
  • any substance that causes an immune system to produce antibodies against it
  • is often a small section of a pathogen protein
26
Q

What is an antibody?

A
  • a protein that binds specifically to a particular substance, its antigen
  • antibodies are known collectively as immunoglobulins (Igs)
27
Q

What are antibodies produced by?

A

B cells

28
Q

What are antibodies function?

A

to identify and neutralize pathogens

29
Q

what is somatic recombination?

A

a mechanism of genetic rearrangement that generates a diverse repertoire of antibodies

30
Q

what do immune cells arise from?

A

stem cells in bone marrow

31
Q

Where to t cells and b cells mature?

A

t cells- thymus
b cells- bone marrow

32
Q

Where to t and b cells migrate to for processing?

A

lymph nodes, spleen, tonsils, appendix, and Peyer’s patches

33
Q

The heavy chain is produced by randomly selecting one gene from which segments?

A
  • 1 of ~40 variable (V) segments
  • 1 of 25 diversity (D) segments
  • 1 of 6 joining (J) segments
34
Q

which region is highly diverse across cells (also where the antigen binds)?

A

variable region

35
Q

What are the paths that stem cells differentiate in the bone marrow?

A
  1. differentiate into B cells in bone marrow
  2. Migrate to thymus to differentiate into T cells
  3. Migrate to tissues, differentiate into dendritic cells & macrophages
36
Q

what happens when immature dendritic cells encounter an antigen?

A

they internalize it, display its fragments on the cell surface, and migrate to lymph nodes, where they activate naive t cells

37
Q

when do dendritic cells mature and what is the implication?

A

mature during migration
lose their ability to engulf pathogens
– will instead deliver one clear signal to T cells

38
Q

how are cytotoxic t cells activated?

A

by dendritic cells undergo rapid clonal expansion and then migrate throughout the body in search of cells exhibiting the corresponding antigens

39
Q

How do t cells kill cells?

A
  1. by damaging the cell membrane, which causes the cell to swell and lyse
  2. through inducing apoptosis, which causes the target cell to shrink and die
40
Q

what happens when b-cell receptors recognize antigens?

A

they activate and undergo rapid clonal expansion and clonal selection, gaining increased ability to recognize foreign antigens

41
Q

What is the first step of clonal selection?

A

somatic recombination

42
Q

What is the second step of clonal selection?

A

B/c receptors created by random recombination, many will bind to self proteins— will be deleted
- end product is a vast diversity of immune receptors

43
Q

What is the third step of clonal selection?

A

After clonal selection, immune cells proliferate rapidly through clonal expansion (creates a large # of cells that react w/ the antigen that has been detected)

44
Q

What is the fourth step of clonal selection?

A

during clonal expansion of b-cells, affinity maturation occurs
- an improved match to the pathogen (part of clonal expansion)

45
Q

What is the fifth step of clonal selection?

A

B cell lineages activated in an immune response set aside some cells to serve as immunological memory

Evolutionary Medicine (17 decks)

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