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Term 2! > BIOL 273 - Unit 6.3 > Flashcards

BIOL 273 - Unit 6.3 Flashcards

1
Q

Basic steps of immune response (regardless of foreign substance)

A
  1. Detection and identification of foreign substance
  2. Communication with other immune cells
  3. Recruitment of help and co-ordination of the response
  4. Destruction or suppression of the invader
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2
Q

What kinds of chemical signalling does the immune response use

A

Antibodies (Ab) - bind to antigen as a signal

Cytokines - affect growth or activity of other cells

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3
Q

What are the two main categories of immunity

A

innate and adaptive immunity
- overlap and cooperate in mounting responses to pathogens

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4
Q

Describe the response time of innate immunity

A

Innate - more rapid , less specific response - can lead to adaptive

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5
Q

Describe the response time of adaptive immunity

A

response is slower, more specific

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6
Q

Describe innate immunity

A

present before pathogen is encountered and is non-specific

response begins within minutes to hours, and it does not remember past infections

some non-specifc cell types and proteins

inflammation is distinctive in innate immune response

Present in all organisms

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7
Q

Describe adaptive immunity

A

directed at specific invaders (aka acquired immunity)

Develops after the pathogen is encountered and the response takes days to weeks

Remembers past infections

Only found in vertebrates

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8
Q

What can adaptive immunity be further divided into

A

Cell-mediated immunity

Antibody mediated immunity (humoral immunity)

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9
Q

Line of defences of innate immunity

A

physical and chemical barriers provide the first line of defence (most vulnerable since exposed to outside)

Second line of defence are patrolling or stationary leukocytes and blood proteins (react same way to every infection)

(provide clearance of pathogens or containment of the pathogen until adaptive response kicks in)

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10
Q

Innate immune system cells

A

Majority are phagocytes (destroyes/suppress invader ingesting it)

Attract other cells by secreting cytokines which will attract other immune cells via chemotaxins
- cells that are attracted are cytokines, products of tissue injury, bacterial products

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11
Q

Describe how phagocytes engulf invaders during phagocytosis (innate immunity)

A

Phagocytes leave the circulation and enter tissue through capillary walls (aka extravasion)

They identify the invader by chemical cues which interacts with receptors on the phagocyte membrane

Many receptors bind sequentially to allow the phagocyte to engulf the invader

Movement of pseudopodia via actin filaments push the cell around invader

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12
Q

What happens in phagocytosis when pathogens do not have surface features that can be recognized directly by phagocyte (innate immunity)

A

blood proteins bind to and coat the pathogen to “tag” it

Phagocytes have receptors for these blood proteins

“Tagging” a pathogen is called opsonization

A protein that can do it is an opsonin

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13
Q

Phagocytosis: what happens once the pathogen is ingested

A

the particle is in a vesicle called a phagosome

These fuse with lysosomes which contain digestive enzymes and chemicals that kill the pathogen
- forms a phagolysosome

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14
Q

Pus

A

Dead phagocytes, tissue fluids and debris collected at the site of injury

Those phagocytes that are also APCs present antigens from digested bacteria on the surface of the APC via class II MHC

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15
Q

Natural killer cells

A

lymphocytes associated with innate immunity
- kills an infected cell that is not presented with MHC I

  • do not have specific receptors as seen in B cells and T cells
  • They bring out apoptosis in pathogen-infected cell
  • Can also attack tumour cells
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16
Q

What do natural killer cells produce

A

cytokines such as interferons ; interfere with viral replication
- IFN alpha and beta - induces an “antiviral state” in nearby cells that prevents viral replication

  • IFN gamma - activates macrophages and other immune cells
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17
Q

Role of chemical mediators

A
  • play a role in the innate response
  • create the inflammatory response - red warm swelling in skin is hallmark of innate response
  • caused by cytokines that are released by macrophages
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18
Q

Describe the purpose of inflammatory response of chemical mediators

A
  • serves as a signal to attract other cells and chemical agents to the site
  • Increase capillary permeability and causes fever
  • A physical barrier is produced - prevent the spread of pathogen
  • tissue repair is promoted
19
Q

Interleukin 1 (IL-1)

A

produced by cells within innate immune system such as macrophages - mediates effects of inflammatory response of chemical mediators

  • act on endothelial cells lining the blood vessels - loosens junctions between cells
  • act on liver cells to produce blood proteins involved in damage control
  • Induce fever
  • Stimulate cytokine production
20
Q

Complement proteins

A
  • take part in innate response (blood proteins)
  • activated by sequential proteolysis
  • some are opsonins, some are chemotaxins , some form membrane attack complex and make holes in pathogen membranes
21
Q

Describe the Membrane Attack complex

A

Use of complement proteins in innate response:
- results in “MAC Attack”

C1 binds to an anitogen antibody complex on an invading pathogen, causing complement components to split in two

proteins continue to split util C3a attracts phagocytes to infection site

fragments joins to form membrane attack complex, which makes a hole in the pathogen’s plasma membrane, water rushed into the hyperosmotic cytoplasm, causing the pathogen to lyse

22
Q

What is adaptive immunity started by

A

products of innate immune response

23
Q

Adaptive immune system cells

A

lymphocytes and lymphocyte products
1. Natural killer (which is in innate response)
2. B cells (activated form = plasma cell)
3. T cells (Tc and Th and Tregs)

24
Q

clone

A

a population of lymphocytes that has a specificty towards one particular antigen

25
Q

Features of lymphocytes of adaptive immune response

A
  • T cells and B cells can be expanded clonally
  • each individual cell recognises a different specific pathogen - known as specificity
  • few naive cells (never encountered specific antigen)
  • once they recognize a pathogen - expand clonally - many effector cells
  • these effector cells attack the pathogen to become memory cells
26
Q

Adaptive immunity; antibody-mediated immunity; what cells take part in this

A
  • B cells produce antibodies that take part in antibody-mediated immunity aka HUMORAL IMMUNITY

Antibodies are proteins that bind specifically and target pathogens for destruction

27
Q

antibodies of antibody mediate immunity

A

AKA IMMUNOGLOBULINS

  • can be either a cell membrane protein or B lymphocytes or secreted
  • membrane Ab’s can be used as markers to identify each different clone of B cells
28
Q

What do stimulated B cells mature into in antibody-mediated immunity

A

mature into plasma cells
- essentially antibody factories (producing many antibody molecules per second)

  • plasma cells are short lived but few memory cells survive
29
Q

Primary antibody response

A

Primary response happens on the first exposure to an antigen
- slower response and less antibody concentration
- delayed response

30
Q

Secondary antibody response

A

happens much faster because of mediated memory cells
- more antibodies produced

31
Q

Why do vaccinations work

A

patient is given an inactivated or partial pathogen
- they generate memory cells that recognize the natural pathogen (if encountered in the future)
- allow memory cells to clonally expand

32
Q

Immunoglobulin: IgM

A
  • produced during primary response (battling pathogen for the first time)
  • activates complement (MAC attack)
33
Q

Immunoglobulin: IgA

A

found in secretions that can interact with specific antigen

neutralize pathogen before entry of body

ex. tears, mucus, salvia

dimer; 2 subunits coming together

34
Q

Immunoglobulin: IgD

A

Found on surface of B cells with IgM

function unknown

35
Q

immunoglobulin: IgG

A

Majority of antibodies in plasma

Secondary response antibody

activates complement

opsonizes

36
Q

Immunoglobulin: IgE

A

allergic response

recognized by mast cells

37
Q

Antibody structure

A
  • four polypeptides linked into a Y shape with 2 light chains and 2 heavy chains
  • each side of the Y is identical (one ligt chain linked to one heavy chain)
  • The arms (Fab) contain the antigen binding sites
  • The stem (Fc) determines which of the five classes an antibody belongs to
  • There is a hinge in between the Fab and Fc portions
38
Q

antibody function

A

do not damage pathogen themselves
- instead, they make pathogens more visible to immune defences or activate
- humoral immunity help initiate innate immunity response
- immune cells recognize stems of antibodies (interaction)

39
Q

seven antibody functions

A
  1. Act as opsonins to tag Ag’s for phagocytosis
  2. Cause antigen/pathogen clumping
  3. Neutralize bacterial toxins
  4. Activate complement
  5. Activate b cells
  6. Activate Ab dependent cellular activity
  7. Activates mast cells to degranulate
40
Q

Adaptive immunity: cell mediated ; what cells are mediate this

A
  • T cells need to be in contact directly with the target cell expressing an antigen
  • T cell receptor (antigen specific molecule) is expressed only as a cell-surface protein
  • Detects Ag presented on the surface of a target cell via the MHC receptor
  • T cell cannot bid to free antigen (must be displayed on class I or class II)
41
Q

Class I MHC

A

present on the surface of every nucleated cell in the body

  • defend against pathogens that get inside cells
  • peptides are presented in MHC class I to cytotoxic T cells (Tc)
  • Tc cells kill the cells that express the peptides
  • Tc cells can also express the Fas ligand to kill target cell via apoptosis
42
Q

What do Class I MHC release

A

perforin - which forms pores in target cell

granzymes - which enter through the pores and trigger apoptosis

43
Q

Class II MHC

A

present on the surface of specialized immune system cells - APC’s b
- cells respond to extracellular pathogens
- Phagocytose pathogens - present peptides in MHC class II to Helper T (Th) cells or regulatory T (Treg) cells

  • Th cells respond by secreting cytokines that activate other immune system cells
  • Treg cells respond by secreting cytokines that suppress other immune system cells

Term 2! (59 decks)

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