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Biol225 > Chapter 43 > Flashcards

Chapter 43 Flashcards

1
Q

Pathogens

A

agents that cause disease

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2
Q

Immune system

A

recognizes foreign bodies and responds with the production of immune cells+proteins

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3
Q

All animals have(a)…vertebrates have(b)…

A

a) Innate immunity; defence active immediately upon infection.
b) adaptive immunity; specific recognition

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4
Q

Innate immunity

A
  • All animals/plants
  • present before any exposure to pathogens
  • effective from time of birth
  • external barriers plus internal cellular+chemical defences.
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5
Q

Adaptive immunity

A

(acquired immunity)

  • develops after exposure to agents
  • involves very specific response to pathogens
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6
Q

Invertebrates innate immunity (insects)

A
  • exoskeleton (chitinous) forms 1st barrier to pathogens
  • digestive system protected by chitin-based barrier and lysozyme (enzyme that breaks down bacterial cell walls)
  • Hemocytes circulate within hemolymph and carry out phagocytosis
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7
Q

Phagocytes

A

ingest and digest foreign substances (ie. bacteria)

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8
Q

Hemocytes

A

also secrete antimicrobial peptides that disrupt plasma membranes of fungi and bacteria

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9
Q

Vertebrate innate immunity defenses

A
  • barriers
  • phagocytes
  • antimicrobial peptides
  • natural killer cells
  • inflammatory response
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10
Q

Cellular innate defenses

A

pathogens entering mammalian body are subject to phagocytosis by WBC’s (which recognize groups of pathogens).

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11
Q

Barrier defences

A
  • skin
  • mucus membranes (respiratory, urinary, reproductive tracts)
  • saliva, tears
  • low pH of skin and digestive system prevents growth of many bacteria
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12
Q

Two types of phagocytic cells

A

WBC engulf invading pathogens; resulting vacuole containing microbe fuses with a lysosome to destroy it.

  1. Neutrophils
  2. Macrophages
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13
Q

Natural killer cells

A

circulate through body and detect abnormal cells

-release chemicals leading to cell death, inhibiting spread of virally infected/cancerous cells.

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14
Q

Antimicrobial peptides and proteins

A

function in innate defence by attacking pathogens or impeding their reproduction.

  • interferons
  • 30 proteins make up complement system
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15
Q

interferon

A

proteins that provide innate defence, interfering with viruses and helping activate macrophages.

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16
Q

Complement system

A

30 proteins make it up, which causes lysis of invading cells, helps trigger inflammation

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17
Q

Inflammatory response

A
  • pain, swelling
  • brought about by molecules released upon injury/infection
  • enhanced blood flow to site helps deliver antimicrobial peptides
  • mast cells (histamine)
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18
Q

Mast cells

A

a type of connective tissues release histamine.

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19
Q

histamine

A

triggers blood vessels to dilate, become more permeable, thus allowing peptides to pass into tissues.

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20
Q

Inflammation can either be…

A

local or systemic (throughout body)

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21
Q

Fever

A

systematic inflammatory response triggered by substances released by macrophages in response to certain pathogens.

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22
Q

Evasion of innate immunity by pathogens

A

some pathogens avoid destruction by modifying their surface, preventing recognition or by resisting breakdown following phagocytosis.
-ie. TB

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23
Q

Adaptive response relies on two types

A

of lymphocytes (WBC’s)

  1. T cells (matured in Thymus)
  2. B cells (T cells that mature in Bone marrow)
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24
Q

Adaptive response

A
  • T or B cells bind to antigens via specific antigen receptors
  • antigen receptors recognize part of one molecule of pathogen
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25
Q

T and B cell adaptive response specialization…

A
  • each individual B or T cell is specialized to recognize a specific type of molecule
  • antigen receptors of B and T cells have similar components, but encounter in a different way.
26
Q

B cell antigen receptor

A

-Y shaped molecule, two identical (heavy chains and light chains)

27
Q

Antigen recognition by B cells and antibodies

A
  • constant regions of chains vary little among B cells, but variable regions differ greatly
  • variable regions provide antigen specificity
  • binding of B cell antigen receptor to an antigen is an early step in B cell activation
28
Q

B cell activation

A
  • gives rise to cells that secrete a soluble form of receptor called antibody (immunoglobulin)
  • secreted antibodies similar to B cell receptors, but lack transmembrane regions that anchor receptors in plasma membrane
29
Q

Antigen recognition by T cells (part 1)

A
  • T cells bind to antigen fragments displayed/presented on a host cell
  • antigen fragments are bound to cell surface proteins (MHC)
30
Q

MHC

A

(Major histocompatibility complex

-molecules are host proteins that display antigen fragments on the cell surface

31
Q

Antigen presentation

A

MHC molecules bind and transport antigen fragments to cell surface.

32
Q

Antigen recognition by T cells (part 2)

A
  • T cell can then bind both the antigen fragment and MCH molecule
  • necessary for the T cell to participate in adaptive immune response.
33
Q

Adaptive immune system (4 major characteristics)

A
  1. immense diversity of lymphocyte borne receptors
  2. Self tolerance; lack of reactivity against an animal’s own molecules
  3. B and T cells proliferate after activation
  4. Immunological memory
34
Q

Origin of self tolerance

A
  • antigen receptors generated by random rearrangement of DNA
  • as lymphocytes mature in bone marrow+thymus, they’re tested for self reactivity
  • B and T cells with receptors specific for body’s own molecules are destroyed by apoptosis, or rendered nonfunctional
35
Q

Apoptosis

A

programmed cell death

36
Q

Proliferation of B and T cells

A
  • in body there are a few lymphocytes with any particular antigen receptors
  • in lymph nodes; antigen is exposed to a steady stream of lymphocytes until a match is made.
  • binding of mature lymphocyte to an antigen initiates events that activate the lymphocyte
  • once activated, B or T cell undergoes multiple cell divisions (clonal selection) to produce a clone of identical cells.
37
Q

Two types of clone cells produced

A
  1. Effector cells (short lived, act immediately against the antigen
  2. Memory cells (long lived, give rise to effector cells if the same antigen is encountered again)
38
Q

Immunological memory

A

-responsible for long term protections against diseases (due to a prior infection of vaccination)

39
Q

Immunological memory responses

A

1st response=primary immune response. selected B and T cells give rise to their effector forms

2nd response=secondary immune response. Memory cells facilitate a faster, more efficient response than the first.

40
Q

Defenses by B and T lymphocytes can be divided into…

A
  1. humoral response

2. cell-mediated immune response

41
Q
  1. humoral immune response
A

antibodies help neutralize or eliminate toxins and pathogens in the blood and lymph

42
Q
  1. cell-mediated immune response
A

specialized T cells destroy affected host cells

43
Q

Helper T cells

A

A response to nearly all antigens

  • trigger both humoral and cell-mediated immune responses
  • signals from Helper T-cells initiate production of antibodies and activate T cells that kill infected cells
  • antigen receptors on surface of helper T cells bind to the antigen and MHC molecule.
  • helper T cell is activated proliferated and forms a clone of helper T cells, which activate appropriate B cells and cytotoxic T cells.
44
Q

Antigen-presenting cells

A

have MHC molecules on their surfaces

-MHC molecules are the basis upon which antigen presenting cells are recognized.

45
Q

Cytotoxic T cells

A

a response to infected cells

  • are effector cells in the cell-mediated immune response
  • use toxic proteins to kill cells infected by viruses or other intracellular pathogens
  • recognize fragments of foreign proteins produced by infected cells and bind to MHC molecules
46
Q

Activated cytotoxic T cells

A

secrete proteins that disrupt the membranes of target cells and trigger apoptosis

47
Q

B cells and antibodies

A

response to extracellular pathogens

  • humoral response is characterized by secretion of antibodies by B cells
  • activation of H.I.R. involves B cells and helper T cells responding to pathogen antigens
48
Q

Activation of B cells

A
  • in response to cytokines from helper T cells and an antigen, a B cell proliferates and differentiates into memory B cells and plasma cells.
  • activated B cell gives rise to thousands of identical plasma cells, which begin producing and secreting antibodies
49
Q

Antibodies don’t kill pathogens, instead they…

A
  • mark pathogens for destruction by macrophages
  • bind to viral surface proteins preventing infection of host cell
  • bind to toxins in body fluids and prevent them from entering body cells
  • bind to a complement protein, triggering a cascade of complement protein activation leading to cell lysis
50
Q

Both humeral and cell-mediated responses can include

A

primary and secondary immune responses

51
Q

Memory cells enable

A

the secondary response

52
Q

Immunization (2 types)

A

both can be induced artificially

  1. Active immunity
  2. Passive immunity
53
Q
  1. Active immunity
A

develops naturally when a pathogen invades the body, elicits a primary or secondary immune response
-can develop following immunization (vaccination)

54
Q
  1. Passive immunity
A

immediate and short-term protection
-conferred when antibodies cross the placenta from mother to fetus, or when antibodies pass from mother to infant (in breastmilk)

55
Q

artificial passive immunization

A

antibodies from an immune animal are injected into a non immune animal

56
Q

Allergies

A

-exaggerated responses to allergens (antigens)

57
Q

localized allergies

A

antibodies produced after first exposure to an allergen attach to receptors on mast cells.

  • next time allergen enters body, it binds to mast cell-associated antibodies.
  • mast cells release histamine and other mediators that cause vascular changes leading to symptoms
  • can also be acute–anaphylaxis
58
Q

Autoimmune diseases

A

individuals own immune system loses tolerance for self, turns against certain molecules of the body

59
Q

evolutionary adaptations of pathogens (immune system avoidance)

A

pathogens have evolved mechanisms that thwart immune responses.

  • prevent recognition through antigenic variation (flu, HIV)
  • some viruses remain in a host in an inactive state (called latency)
60
Q

Antigenic variation

A
  • human influenza virus mutates rapidly (basis of annual new strain of flu vaccines)
  • human viruses occasionally exchange genes with viruses of domesticated animals
  • poses a danger as human immune systems are unable to recognize the new viral strain
61
Q

HIV

A

persists in the host, despite an immune response because it has a high mutation rate that promotes antigen variation
-over time, if untreated; infection not only avoids the adaptive immune response, it abolishes it.

Biol225 (7 decks)

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