Chapter 43 Flashcards
1
Q
Pathogens
A
agents that cause disease
2
Q
Immune system
A
recognizes foreign bodies and responds with the production of immune cells+proteins
3
Q
All animals have(a)…vertebrates have(b)…
A
a) Innate immunity; defence active immediately upon infection.
b) adaptive immunity; specific recognition
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.
5
Q
Adaptive immunity
A
(acquired immunity)
- develops after exposure to agents
- involves very specific response to pathogens
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
7
Q
Phagocytes
A
ingest and digest foreign substances (ie. bacteria)
8
Q
Hemocytes
A
also secrete antimicrobial peptides that disrupt plasma membranes of fungi and bacteria
9
Q
Vertebrate innate immunity defenses
A
- barriers
- phagocytes
- antimicrobial peptides
- natural killer cells
- inflammatory response
10
Q
Cellular innate defenses
A
pathogens entering mammalian body are subject to phagocytosis by WBC’s (which recognize groups of pathogens).
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
12
Q
Two types of phagocytic cells
A
WBC engulf invading pathogens; resulting vacuole containing microbe fuses with a lysosome to destroy it.
- Neutrophils
- Macrophages
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.
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
15
Q
interferon
A
proteins that provide innate defence, interfering with viruses and helping activate macrophages.
16
Q
Complement system
A
30 proteins make it up, which causes lysis of invading cells, helps trigger inflammation
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)
18
Q
Mast cells
A
a type of connective tissues release histamine.
19
Q
histamine
A
triggers blood vessels to dilate, become more permeable, thus allowing peptides to pass into tissues.
20
Q
Inflammation can either be…
A
local or systemic (throughout body)
21
Q
Fever
A
systematic inflammatory response triggered by substances released by macrophages in response to certain pathogens.
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
23
Q
Adaptive response relies on two types
A
of lymphocytes (WBC’s)
- T cells (matured in Thymus)
- B cells (T cells that mature in Bone marrow)
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
25
T and B cell adaptive response specialization...
- 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
B cell antigen receptor
-Y shaped molecule, two identical (heavy chains and light chains)
27
Antigen recognition by B cells and antibodies
- 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
B cell activation
- 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
Antigen recognition by T cells (part 1)
- T cells bind to antigen fragments displayed/presented on a host cell
- antigen fragments are bound to cell surface proteins (MHC)
30
MHC
(Major histocompatibility complex
| -molecules are host proteins that display antigen fragments on the cell surface
31
Antigen presentation
MHC molecules bind and transport antigen fragments to cell surface.
32
Antigen recognition by T cells (part 2)
- T cell can then bind both the antigen fragment and MCH molecule
- necessary for the T cell to participate in adaptive immune response.
33
Adaptive immune system (4 major characteristics)
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
Origin of self tolerance
- 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
Apoptosis
programmed cell death
36
Proliferation of B and T cells
- 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
Two types of clone cells produced
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
Immunological memory
-responsible for long term protections against diseases (due to a prior infection of vaccination)
39
Immunological memory responses
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
Defenses by B and T lymphocytes can be divided into...
1. humoral response
| 2. cell-mediated immune response
41
1. humoral immune response
antibodies help neutralize or eliminate toxins and pathogens in the blood and lymph
42
2. cell-mediated immune response
specialized T cells destroy affected host cells
43
Helper T cells
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
Antigen-presenting cells
have MHC molecules on their surfaces
| -MHC molecules are the basis upon which antigen presenting cells are recognized.
45
Cytotoxic T cells
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
Activated cytotoxic T cells
secrete proteins that disrupt the membranes of target cells and trigger apoptosis
47
B cells and antibodies
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
Activation of B cells
- 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
Antibodies don't kill pathogens, instead they...
- 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
Both humeral and cell-mediated responses can include
primary and secondary immune responses
51
Memory cells enable
the secondary response
52
Immunization (2 types)
both can be induced artificially
1. Active immunity
2. Passive immunity
53
1. Active immunity
develops naturally when a pathogen invades the body, elicits a primary or secondary immune response
-can develop following immunization (vaccination)
54
2. Passive immunity
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
artificial passive immunization
antibodies from an immune animal are injected into a non immune animal
56
Allergies
-exaggerated responses to allergens (antigens)
57
localized allergies
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
Autoimmune diseases
individuals own immune system loses tolerance for self, turns against certain molecules of the body
59
evolutionary adaptations of pathogens (immune system avoidance)
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
Antigenic variation
- 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
HIV
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.
