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Microbiology > 5. Immunity and Host Defense > Flashcards

5. Immunity and Host Defense Flashcards

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1
Q

What is the immune system

A

fights off foreign material that threatens the body
- protects against disease

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2
Q

2 Branches of immune system- specificity, memory, respond rate

A
  1. Innate
    - born with it
    - non-specific
    - no memory component
    - responds rapidly
  2. Adaptive
    - highly specific
    - memory component
    - responds in a few days
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3
Q

Can you use both branches of the immune system at the same time

A

yes! not mutually exclusive

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4
Q

Innate immune system

A
  • protects humans from most infectious diseases
  • exists at birth and always present
  • natural host resistance (microbiota)
  • no memory
  • can be specific for a particular tissue
  • physical barrier, chemical defenses, cellular defenses, molecular defenses, physiological processes
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5
Q

Innate: Infection site and tissue specificity

A

pathogens prefer a specific body site to initiate infection
- based on nutritional and metabolic needs
- mechanism of spread (aerosols vs blood/bodily fluids)

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6
Q

Ex of bacteria that can be ingested into deep wounds

A

Clostridium tetani

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7
Q

Innate: natural host resistance and examples

A
  • illness from pathogens varies from one species to another
  • anthrax - causes fatal blood infection in cattle and cutaneous infection in humans
  • HIV - infect human cells but not mice or guinea pig
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8
Q

Physical barriers to infection

A
  1. Skin
  2. Mucous membranes
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9
Q

Skin

A
  • prevents invasion by microbes
    -has protein (keratin) that is thick
  • slightly acidic (5)
  • high NaCl - for drying
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10
Q

What can grow on skin surface

A
  • Some fungal infections can grow right on the skins surface (but needs broken skin to cause infection)
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11
Q

Mucous membranes

A
  • line tracts in the body - resp, digestive, reproductive, urinary
  • mucus produced by goblet cells - traps microbes to prevent infection
  • contains microbial secretions
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12
Q

Mucous membranes in resp tract

A
  • contains the mucocilliary escalator
  • mucosal epithelial cells contain cilia - serve to filter incoming air
  • sweeping action of cilia allows the removal of mucous and trapped microbes from the lungs
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13
Q

Mucous membranes in gastrointestinal tract

A
  1. stomach
    - acidic (pH = 2)
    - proteases
  2. small intestine
    - pancreatic juice buffers acidity of incoming contents from stomach (pH of 7) and containes enzymes
    - bile from liver
  3. large intestine
    - normal microbiota
    - normal resident that live symbiotically inside of the colon
    - use attachment sites to stay inside colon
    - competitive exclusion - consume undigested nutrients
    - microbial antagonism - produce antimicrobial compounds
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14
Q

Mucous membranes in genitourinary tract

A
  • contains urine - toxins that are intolerable by bacteria
  • act of urinating removes these contamianting microbes
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15
Q

female urinary tract

A
  • contains normal microbiota
  • glycogen secreted by vagina epithelial cells supplies nutrients for microbial growth
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16
Q

Ex of bacteria found in female urinary tract

A

lactobacillus acidophilus
- ferments glucose to lactic acid
- pH of 4.5

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17
Q

Lymphatic system

A
  • Composed of organs and vessels that allow immune cells to contact foreign antigenic material
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18
Q

Antigen

A

foreign material that is able to activate cells of the immune system

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19
Q

Components of the lymphatic system

A
  1. lymphatic vessels
    - Carry lymph from the tissues to the lymph nodes (unidirectional - away from tissues)
    - Lymph is rich in leukocytes (wbc) and no erythrocytes (rbc)
  2. Lymphoid organs
    - primary and secondary
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20
Q

Primary lymphoid organs

A
  1. Bone marrow - where leukocytes are produced
  2. thymus gland - some leukocytes mature here
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21
Q

Secondary lymphoid organs

A
  1. lymph nodes
  2. spleen
  3. MALTS (mucosa associated lymphatic tissue - mucus membrane
    **These all contain high concentration of leukocytes and incoming lymph is filtered (removing microbes)
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22
Q

MALT and GALT

A

mucosa associated lymphatic tissue
gut associated lymphatic tissue - leukocytes present here are constantly phagocytosing material in their surroundings in search of foreign content

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23
Q
A
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24
Q

Cellular defenses: leukocytes - location

A
  • circulate in the blood and lymphatic system
  • reside in the tissues and lymph nodes
  • play a role in both innate and adaptive immunity
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25
Q

granulocytes - type of, what it looks like, func

A
  • category of leukocytes
  • large visible granules in the cytoplasm
  • granules are reactive

2 functions:
-kill microbes
-signalling molecule for other components of the immune system

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26
Q

types of granulocytes

A
  1. neutrophils
  2. eosinophils
  3. basophils and mast cells
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27
Q

Neutrophils - function, location, stain, granules contain

A
  • strongly phagocytic
  • cytoplasmic granules contain lysozyme and defensins
  • circulate in blood (exit the capillaries during periods of infection
  • stain: no basic + acidic dyes
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28
Q

Eosinophils - function, location, stain

A
  • non-phagocytic
  • cytoplasmic granules will stain with acidic dyes
  • work to destroy large parasitic cells like protozoa and parasitic worms
  • secrete-extra-cellular enzymes and reactive oxygen species
  • can also exit the capillaries into infected tissues
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29
Q

Basophils and Mast Cells - function, location, stain

A
  • not strongly phagocytic
  • cytoplasmic granules stain with basic dyes
  • basophils circulate in blood
  • mast cells reside in mucosal tissue
  • degranulate in response to stimuli and releases histamine
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30
Q

what happens when histamine is released systemically and which cells do this?

A

causes life threatening vasodilation and bronchioconstriction

basophils and mast cells:
- important part of the allergic response
- causes vasodilation locally

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31
Q

agranulocytes (2nd category of leukocytes)

A
  • contain cytoplasmic granules that are much smaller and difficult to view than granulocytes
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32
Q

types of agranulocytes

A
  1. monocytes
  2. lymphocytes
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33
Q

monocytes - location and function

A
  • circulate in blood
  • once in the tissues they are strongly phagocytic
  • present foreign antigen to other cells of immune system
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34
Q

types of monocytes

A
  1. macrophages
  2. dendritic cells

only turn into these when they migrate into tissues and mature

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35
Q

macrophages

A

location:
- tissues
- lungs, connective tissue, spleen and liver

function:
- contain surface TLR (toll-like-receptors): recognize many pathogens like LPS, peptidoglycan, elements of the fungal cell wall
- induces phagocytosis

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36
Q

dendritic cells - location and function

A

Location:
- tissues that are often sites of entry for infectious material
- mucus membranes of the nose, lungs and intestines

Function:
- regularly sample the surroundings and phagocytose antigens
- phagocytosed antigen is carried to lymphoid organs
- presented to other cells of immune system (T/B Lymphocytes)
- activate the adaptive immune response

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37
Q

name of dendritic cells in skin

A

langerhans cell

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38
Q
A
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39
Q

lymphocyte

A
  • leukocytes that are involved in the adaptive immune response
  • circulate through the blood and remain in lymphoid organs
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40
Q

types of lymphocytes

A
  1. b-lympho
  2. t-lympho
  3. NK (natural killer)
41
Q

B lymphocytes

A
  • also called B cells or plasma cells
  • antibody producing/secreting cells
  • form the main component of humoral immunity
42
Q

T lymphocytes

A
  • aka T cells
  • different types
  • form the main component of cell mediated immunity
43
Q

Natural killer cells

A

destroy abnormal cells in the body ( cancer and infections)

44
Q

Molecular defenses

A
  • secreted at mucosal sites:
    1. lysozyme (breaks the beta 1-4 linkage)
    2. defensins (puncture holes in the cell membrane
45
Q

Phagocytosis

A
  • destroy pathogens that may have never before been encountered in the body
  • involves leukocytes capable of phagocytosisst
46
Q

Steps in phagocytosis (innate)

A
  1. neutrophils and macrophages recognize PAMPS
    (pathogen associated molecular patterns)
    -LPS, lipotechoic acid, flagellin
  2. PAMPS are recognized by TLRs located on the surface of phagocytic cells
    - TLRs are also called pattern recognition receptors
    - interaction of PAMP with a TLR triggers phagocytosis
  3. Phagocyte engulf and destroy invading microbes
    - cell membrane invaginates around a foreign particle
    - engulfs it into a phagosome
    - phagosome fuses with a lysosome to form a phagolysosome (oxygen-independent)
    OR
    - Activated phagocytes produce reactive oxygen compounds
    - kill ingested microbes by oxidizing cell components (oxygen dependent killing)
47
Q

What is phagolysozome filled with

A

lysozyme and defensins
proteases - degrades protein
lipases - degrade phospholipids
nuclease - degrade nucleicacids

48
Q

What happens when invaders have been killed in phagocytosis (innate immune)

A
  • neutrophils form exocytosis - fragments are expelled from the cell
  • macrophages and dendritic cells become antigen presenting cells
  • fragments of the intruder are presented on the cell surface to trigger an adaptive immune response
49
Q
A
50
Q

inflammation

A

occurs non-specifically in response to tissue damage, toxins and infectious material

51
Q

5 cardinal signs of inflammation

A

redness, warmth, pain, swelling and loss of function

52
Q

responses to infection injured tissue and leukocytes

A
  1. leukocyties release pro-inflammatory cytokines
    - blood vessels dilate
    - allows more leukocytes to access the area
  2. vessel walls become more permeable
    - leukocytes can squeeze into tissues (extravasation)
    - attack invading pathogens
  3. temperature increase may slow down the growth of pathogens
    - promotes healing of damage tissue as well
  4. blood leaking into tissues spaces can clot
    - prevents movement of pathogens
53
Q
A
54
Q

Fever

A

Increase in body temp
- controlled by the hypothalamus
- triggered by toxins, LPS and chemicals produced by immune system
- all of these things reset the bodies thermostats

55
Q

Results of a fever

A
  1. muscle contraction - shivering
  2. increased temp
    - faster metabolism
    - faster phagocytosis
    - faster healing
    - slower growth of microbes (growth slows at 40 degrees)

defense:
- against disease
- over 40 degrees

56
Q

Definition of adaptive immune system: acquired

A
  • begins as soon as a pathogen is acquired for the first time
  • adaptive response will not occur until a pathogen is encountered
57
Q

Definition of adaptive immune system: very specific

A
  • very targetted to a specific feature of a given bacterium, virus or toxin
  • immunity to one pathogen will not confer immunity to another
58
Q

Definition of adaptive immune system: memory component

A
  • produces a more effective response when a pathogen is encountered for the second time - faster and stronger
59
Q

the 2 components of adaptive immune system

A
  1. humoral immunity - antibody mediated: b and plasma cells
  2. cell mediated immunity: b and t cells
60
Q

antibodies

A

proteins produced by the immune system that bind and inactivate foreign antigens

61
Q

immunogens

A
  • any foreign material that has the ability to active the adaptive immune system
  • normal protein, polysach, lipid material
62
Q

are immunogens and antigens the same thing

A

for this course yes

63
Q

epitomes

A

actual portion of the antigen that binds to the antibody
a single antigen will have more than one epitome
- increases the ability of an antigen to activate the immune system (immunogenicity)
- each epitome requires a distinct antibody

64
Q

hapten

A
  • low molecular weight compound that is too small on its own to activate adaptive immunity
  • not immunogenic
  • can bind to other molecules such as protein in blood and tissuess
  • becomes strongly immunogenic
65
Q

Example of haptens

A

penicillin!

66
Q

What are antibodies (Ab) made of

A

glycosylated protein molecules (aka immunoglobins - lg)
4 subunits
- 2 identical heavy chains
- 2 idnetical light chains
Chains are assembled into 3 distinct regions
- 2 identical variable regions (FAB) - provide specificity of the antibody
- 1 constant region (FC) - interaction with immune cells - based on differences in the FC region

67
Q

5 types of antibodies

A
  1. immunoglobin G (igG)
    2 immunoglobin A (igA)
  2. immunoglobin M (igM)
  3. immunoglobin E (igE)
  4. immunoglobin D (igD)
68
Q

Immuniglobin M (igM)

A

Pentameric
- 5 different units
Always the first antibody to be produced in response to antigen - primary antibody response
Found on surface of B-lymph
- remains in blood and unable to enter tissue
- Low affinity for antigen
- good for agglutination (cross linking)

69
Q

immunoglobulin G

A
  • monomer
  • predominant antibody in blood
  • presented in tissues
  • binds strongly
70
Q

immunoglobulin A

A

Dimeric
• Secreted at mucosal sites
• Saliva, tears, mucous
• Important defense against respiratory,
reproductive, digestive tract infections

71
Q

Immunoglobulin D (IgD):

A

Monomer
• Located on the surface of B cells
• Important in activation of B cells to begin
producing antibody against a specific antigen

72
Q

Immunoglobulin E (IgE):

A

Monomer
• Binds to receptors located on the surface of
mast cells and basophils
• Binding of IgE-antigen complex triggers
degranulation and histamine release
• Allergy

73
Q

igE

A
74
Q
A
75
Q

Five major antibody function

A
  1. neutralization
  2. opsonization
  3. agglutination
  4. anitbody mediated cytotoxicity
  5. complement activation
76
Q

neutralization

A
  • neutralizing the toxin
  • antibodies bind to antigen blocking attachment sites
  • prevents bacteria, virus and toxin entry into tissue and host cells
77
Q

opsonization

A
  • antibodies coat the surface of the bacterial cells
  • attracts phagocytes
  • greatly enhances the rate of phagocytosis
  • phagocyte has the ability to interact with the fc region of the antibody
78
Q

agglutination

A
  • aka crosslinking
  • each class of antibody can bind to a minimum of 2 identical antigen units
  • clumps together many antigens
  • allows phagocytosis to occur more efficiently
79
Q

antibody mediated cytotoxicity

A

attachment of antibody to parasites recruits eosinophils
- eosinphils attach to the fc component of antibodies
- activated eosinophil releases reactive oxygen species and hydrolytic enzymes
- parasite is destroyed

80
Q

complement activation

A
  • a system consisting of a series of proteins found in the blood
  • activated by antibody that is bound to a bacterial cell (classical pathway of complement activation)
  • create a number of different immune responses when activated
  • membrane attack complex (MAC) forms - inserts into the membrane of bacterial cell forming a pore
  • contents of the cell leak and the bacterium dies
81
Q

extra pics of complement activation

A
82
Q

activation of antibody mediated immunity

A
  • b cells are antigen presenting cells
  • macrophages and dendritic cells also perform antigen presentation
  • all antigen presenting cells can insert MHC II (major histo complex) into the plasma membrane
83
Q

Antibodies are produced against ________

A

antibodies are produced against exogenous antigen
- antigen that exists outside of the cell in the surrounding extra-cellular fluid
- can be bacteria, virus, parasite, toxin
- once antibodies are secreted from B cells they can bind to and neutralize/opsonize these exogenous antigens

84
Q

Steps in antibody production

A
  1. B cell phagocytoses exogenous antigen
  2. T helper cells bind to MHC II-Antigen complex resulting in T helper cell activation
  3. Some of these newly produced B cells will become plasma cells
85
Q

Step 1 of antibody production in detail

A

B cell phagocytoses exogenous antigen
- digested content in the phagolysosome will not be exocytosed to the extracellular fluid
- instead it will be complexed together with MHC II (presented on surface) and inserted into the plasma membrane

86
Q

Step 2 of antibody production in detail

A

T-helper cells bind to MHC II-Antigen complex resulting in T helper cell activation
- the activated T helper cell releases cytokines that bind to receptors on the B-cell resulting in B-cell proliferation (aka making more of B-cell)

87
Q

Step 3 of antibody production in detail

A

Cells turn into either
1. B cells to plasma cells
- Actively transcribe, translate and secrete an identical antibody protein to the extra-cellular fluid (specific to exogenous antigen
2. B cells to memory cells
- Used in encounters with the same antigen
- not produce antibodies during current response

88
Q

Primary antibody response

A
  • OCCURS: the very first time a specific antigen is encountered - (can be natural encounter or an artificial encounter like a vaxx)
  • PRODUCES: a weak antibody mediated response - slow production of low levels of antibody
  • RESULTS: memory B cells
89
Q

Secondary antibody response

A
  • OCCURS: every additional time after the primary response when it sees a specific antigen
  • PRODUCES: strong antibody mediated response - rapid production of antibodys - so rapid that the pathogen wont establish infection - no disease
90
Q

explain this pic

A
91
Q

Tolerance

A
  • prevents immune responses against self-antigens
  • any immune cells that are found to recognize self-antigens are destroyed early on in development
  • helps prevent auto-immune disease (when the body turns on itself
92
Q

Cell mediated immunity

A
  • recognizes and destroys abnormal cells present in the body
  • cells infected with the virus/obligate intracellular bacteria
  • endogenous antigen - INSIDE HOST CELL
93
Q

what cells do cell mediated immunity involve

A

cytotoxic T cells

94
Q

How does cell mediated immunity work

A
  • the diseased host cell will display the endogenous antigen in the plasma membrane complexed together with MHC I
  • Cytotoxic T cells will bind to MHC I-antigen complex using their T cell receptor (TCR)
  • This activates the cytotoxic T cell triggering it to release enzymes that cause death of the infected host cell
95
Q

what enzymes do cytotoxic T cells release

A

perforins and granzymes

96
Q

In order to clear a viral infection …

A

you need both antibody mediated immunity and cell mediated immunity

97
Q
A
98
Q

cytotoxic t cells bind to

A

CD8+

99
Q

MHC 2 cells bind to
MHC 1 cells bind to

A

2 - all nucleated cells
1 - antigen presenting cells

Microbiology (8 decks)

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