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MICR 2420 > The Innate Immune System > Flashcards

The Innate Immune System Flashcards

1
Q

what is the difference between infection and disease?

A

if the number of infecting organisms is small and the immune system is effective, a person will not get sick

to cause disease, a pathogen must: breach host defenses, survive innate defense mechanisms, multiply

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2
Q

what are the physical barriers to infection?

A

skin (contains keratin)
mucous membranes (epithelial cells tightly connected, supports barrier function, selectively permeable)
lungs (mucociliatory escalator to remove small particles, microbes are trapped in nose and cilia lining upper airway)

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3
Q

what does SALT stand for?

A

Skin Associated Lymphoid Tissue

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4
Q

what does GALT stand for:

A

Gut Associated Lymphoid Tissue

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5
Q

what are primary lymphoid organs?

A

factory for lymphoid cells

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6
Q

what are secondary lymphoid organs?

A

stations for antigen encounters

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7
Q

what are complements?

A

set of proteins made by the liver
complement antibodies in the killing of bacteria

circulate in blood, enter tissue all over body
circulate as inactive forms and are proteolytically cleaved to activate

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8
Q

what are the three complement activation pathways?

A

classical
lectin
alternative

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9
Q

how do all complement pathways converge?

A

LYTIC

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10
Q

what are the components of the alternative pathway?

A

C3b - acts as an OPSONIN (proteins that coat pathogens)
C3a and C5 - anaphylotoxins, direct immune cell traffic to where it’s most needed
MEMBRANE ATTACK COMPLEX - punch holes in target cells, killing them

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11
Q

what are cytokines?

A

molecules secretes by a cell that can effect other cells
ex. interferon, which act as an alarm bell, helping other cells nearby fend off the virus

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12
Q

what molecule is found in the gut?

A

high concentration of DEFENSINS

higher concentration in close proximity to the crypts of the epithelium

secreted from crypts

keeps out even normal microbiota

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13
Q

what defence cells are found in white blood cells?

A

polymorphonuclear leukocytes
monocytes
macrophages
dendritic cells
mast cells
lymphocytes

1 litre of human blood contains 6 billion WBCs

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14
Q

what do myeloid bone marrow stem cells differentiate into?

A

PHAGOCYTES

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15
Q

why are bacterial cells hard to catch?

A

REPULSION
bacterial cells carry a negative charge, so do phagocytes

C3b binds to the surface of proteins, making it easier for phagocytes to bind

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16
Q

describe NEUTROPHILS

A

capture pathogens with NETs
sense and invader and spews a latticework of chromatin and antimicrobial compounds
prevents spread of the pathogen
allows rapid phagocytosis

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17
Q

what can interfere with NETosis?

A

a CAPSULE

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18
Q

what are monocytes?

A

differentiate into macrophages
circulate in the blood stream
attracted to by cytokines to where they are needed
differentiate while travelling through blood vessels

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19
Q

what are macrophages?

A

large structures that can ingest many microbes at once

can also be found in organs
ex. kuppfer cells in the liver, langerhans in the skin, microglia in the brain, alveolar macrophages in the lung

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20
Q

what are dendrocytes?

A

finger-like projections, give cells a bigger surface area
posess long protrusions that can squeeze through tight spaces into samples

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21
Q

what is inflammation?

A

a key part of the innate immune response

signs: heat at site, edema, redness, pain, altered function (cell is dealing with infection)

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22
Q

what is pus?

A

dead neutrophils

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23
Q

why is long term inflammation bad?

A

extremely hard to kill some microbes - have a thick cell wall and slow reproduction time

ex. mycobacterium tuberculosis, fish tank granuloma, chrones disease

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24
Q

describe phagocytes as antigen presenting cells?

A

process the antigens they ingest and display them on their surface for T-cells

link between innate and adaptive immune system

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25
Q

what are peyer’s paches?

A

specialist sites within the small intestine

rich in “M-cells”, uptake of antigens in the gut to present to macrophages

help body differentiate between friend and foe

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26
Q

how do pathogens evade the immune system?

A

CAPSULES - slippery, stain with India Ink

ex. strep. pneumoniae, neisseria meningitidis, bacillus anthracis

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27
Q

how are pathogens recognized by the immune system?

A

specialized set of receptors that recognize INVARIANT and ESSENTIAL microbial factors that are UNIQUE to the immune system

called: PATTERN RECOGNITION RECEPTORS
recognize: MICROBE ASSOCIATES MOLECULAR PATTERNS

do NOT discriminate between good and bad

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28
Q

what are Toll-like receptors?

A

TRANSMEMBRANE receptors on some IMMUNE cells that RECOGNIZE VIRAL AND BACTERIAL PRODUCTS

ligand bonding (molecule that binds to another molecule to send signals between cells): stimulate CYTOKINES to signal inflammatory response

induce macrophage response

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29
Q

what are NODs and NOD-LIKE RECEPTORS?

A

used if pathogen is INSIDE a host cell
bind to MAMPs and activate cytokine production
form an INFLAMMASOME that activates apoptosis (“good” cell death)

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30
Q

what are the types of cell death?

A

NECROSIS: “bad” cell death, leakage of cellular components, triggers cell death

APOPTOSIS: packages up nicely, phagocytosis of cells and fragments

31
Q

how many toll-like receptors are there?

A

SEVEN
**MISSING 7 and 8
1,2,4,5,9 –> recognize BACTERIA
3 –> recognize viruses
6 –> recognizes mycoplasma

LGDLFDU

OUTSIDE CELL

32
Q

how many NOD-like receptors are there?

A

FOUR
1 –> grame NEGATIVE bacteria
2-4 –> bacteria

CPPF

INSIDE CELL

33
Q

what are inflammasomes?

A

protein complexes that allow rapid secretion of cytokines

34
Q

what are NATURAL KILLER CELLS?

A

NOT PHAGOCYTIC

large and granular

role in innate defense

ATTACK HOST CELLS THAT HAVE BECOME OVERWHELMED BY PATHOGENS

35
Q

describe the mechanism of NKCs

A

ALERTED by interferons or cytokines

infected host signals an ALTERED SELF response

NK cell binds to infected cell, punches holes in membrane

GRANZYME moves through pores, triggers APOPTOSIS

36
Q

what is EFFEROCYTOSIS?

A

allows dying cell to be neatly packaged before death

small enough for neutrophils to consume via EFFEROCYTOSIS

neutrophils dispose of apoptotic cell bodies WITH intruder microbes

inflammation kept to a minimum

37
Q

what is the adaptive immune system

A

branch with MEMORY

38
Q

what are the types of adaptive immune?

A

T-cells: RECOGNIZE antigens on infected cells, TARGET infections

B-cells: ANTIBODIES target invaders, target infections of the body’s fluids

like a WEAPONS CACHE

39
Q

describe adaptive immunity

A

develops 3-4 days following exposure to invading microbe

recognizes small pieces of a given antigen - EPITOPES, produced by PHAGOCYTOSIS

40
Q

what are HAPTENS?

A

a molecule that is too small to elicit an immune response, must be BOUND to another molecule to act as an antigen

41
Q

what macromolecules elicits the best immune response?

A

IMMUNOGENICITY

  1. Proteins –> greatest diversity in shape
  2. Carbs
  3. Nucleic acids and lipids
42
Q

describe T-cell education

A

happens in the THYMUS
begins shortly before birth
thymus shrinks as we grow older

as cells mature, they develop a T-cell RECEPTOR –> each receptor recognizes a different antigen

43
Q

describe “thymus college”

A

T-cells must be able to identify MHC peptides, tested for reactivity against self-antigens

understand commands, well disciplined

98% of T-cells are KILLED

44
Q

what are the types of “effector” T-cells?

A

CYTOTOXIC T-cells: trained ASSASSINS, destroy cells presenting noxious antigens

HELPER T-cells: memorize databanks of antigens and ALERT B-cells if a circulating antigen is detected

45
Q

what are MEMORY t-cells?

A

retain antigen affinity
act as effector cells during reinfection
short lifecycle, replicate

hazy memory over time, why we need booster shots

46
Q

what are REGULATORY t-cells?

A

RESTORE HOMEOSTASIS after infection

lack of these cause chronic inflammation

47
Q

what are MHC proteins?

A

the proteins infected cells place on antigens to display to the immune system

infected cell loads antigen to show they are infected

allows T-cells to recognize self vs antigen

48
Q

what is MHC1?

A

display antigens on the SURFACE of the infected cell

49
Q

what is MHCII?

A

display antigens on the surface of APCs

50
Q

what is the initiation of cell-mediated reponse?

A

APCs that have phagocytosed a pathogen travel to lymph nodes to display captured antigens to display captured antigens

binding of antigen loaded MHCs to receptors activates T-cells, cell-mediated adaptive immune response begins

cytotoxic T-cells can directly kill an infected host

51
Q

describe t-cell deployment

A

travel to LYMPH NODES
otherwise, t-cells and APCS will not find each other

4x10^11 t-cells in body
10 T-cells will recognize same pattern - CLONOTYPE

52
Q

describe helper T-cells and the humoral response

A

some T-cells activate B-cells

B-cells undergo education in bone marrow, only recognize 1 antigen epitope

B cell activates when a helper T-cell presents the same antigen to a B-cell as the one on its receptor

53
Q

what do B-cells differentiate into?

A

PLASMA cells

live 4-5 days, but produce 2000 antibodies per second

54
Q

what is B cell and T-cell tolerance

A

ANTIGEN DOSE
if the antigen does is over the threshold value, B and T cells become overstimulated, do not respond

realize it is not killing you

55
Q

describe the anatomy of an antibody

A

forms a T shape

top is antigen binding site (F(ab))
pepsin cleavage site in the middle
Fc fragment at the bottom

56
Q

what binds antibodies together?

A

disulfide bonds

57
Q

how many polypeptide chains are in an antibody?

A

4 - 2 heavy, 2 light

58
Q

what are constant regions?

A

conserved amino acid sequences
5 heavy chain types: alpha, mew, gamma, delta, epsilon (defines antibody class)
2 light chain types: Kappa, lambda

59
Q

what is an isotype?

A

defines various chains belonging to a SPECIES

60
Q

what is an allotype?

A

differences in the constant region shared by some, but not all, members of a species

61
Q

what is an idiotype?

A

differences in hypervariable region within an individual

REMEMBER: idiots are hyper

62
Q

what is IgG?

A

simplest, smallest, most ABUNDANT
4 classes
binds and opsonizes microbes
neutralizes viruses
activates classical pathway

63
Q

what is IgA

A

secreted antibody my MUCOSAL surfaces
found as a DIMER –> can bind 4 antigens
secretory piece wrapped around both molecules during secretion
found in tears, breast milk, mucose

64
Q

IgM

A

can be found as MONOMERS on B-cells
most commonly found as a pentamer
can bind to 10 antigens
FIRST antibody detected during infection

65
Q

what is IgD?

A

trace amounts, in blood
monomeric on surface of B-cells
does not bind to complement

66
Q

what is IgE?

A

trace amounts in blood
more prominently of surface of mast cells and basophils
cells degranulate and amplify immune response
AMPLIFY body’s response to invaders

67
Q

what are allergies

A

IgE triggers release of chemicals such as histamines from mast cells or leukotrienes

harmless antigens perceived as threats

68
Q

what is anaphylaxis?

A

severe form of an allergy
excess histamine triggers smooth muscle contraction in lungs, weakens junctions between cells lining blood vessels

epipens: block process of degranulation. deliver spinephrine

69
Q

describe complement as part of adaptive immunity

A

alternative pathway: C3b binds to bacteria –> forms MAC

antibodies made activate complement through the classical pathway

70
Q

what is the classical pathway?

A

C1 complex binds Fc region

C1 cleaves C4 and C2 –> rejoin to make C3 convertase

C3 cleaves into C3a and C3b

C3B JOINS C3 CONVERTASE TO MAKE C5 CONVERTASE

convertase cleaves C5 to C5a and C5b

C5b forms MAC

71
Q

how is the lectin path similar?

A

lectins produced in liver, bind to sugars on bacterial cells
trigger formation of C3 convertase
same as classical pathway

72
Q

why do we need 3 pathways?

A

people missing pathways susceptible to blood-borne illnesses –> shape shifting pathogens

change antigens regularly to elude immune system

ex. Neisseria meningitidis, neisseria gonorrhoeae, salmonella typhi

73
Q

what are the components of the gut microbiome?

A
  1. epithelial barrier: studded with T-cells
  2. Dendritic cells: between epithelial cells to sample antigens
  3. M cells also sample antigens

sIgA –> coats microbita components considers a threat

74
Q

where are there the most TLRs?

A

on the lumen facing side of epithelial cells (see more antigens)

less on basal side

MICR 2420 (9 decks)

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