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Flashcards in Immunity Deck (42)
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1

Describe how co-stimulation is used

When TCRs bind to their specific MHC (usually class 2), a signal is produced which causes CD28 (found on T cells) to bind to B7-2 (found on APCs)

 

This upregulates CTLA-4 and B7-1, which downregulates any further immune response

2

Explain Fc mediated effects

The Fc region is the bottom part of the antibody

 

Its effects will change dependent on what type of receptor/cell it binds to, as well as the type of immunuglobulin that is present (eg, A,D,G....)

 

Eg, when bound to a mast cell, degranulation occurs....releasing histamine

Whilst binding to a neutrophil will cause phagocytosis of the attatched microbe/pathogen

3

What are inactivated vaccines?

These are not alive and cannot replicate, so cannot form a disease state....even in the immunocompromised

 

Produced by culturing the virus/bacteria in a media, and then inactivation by heat/chemicals

 

This can be expensive, and people can have hypersensitivities to them

4

What are the 4 types of hypersensitivity reactions?

I - Immediate Hypersensitivity (allergy)

 

II - Autoantibodies

 

III - Deposition of immune complexes

 

IV - T cell mediated tissue injury

5

How are B cells and T cells activated?

The B cell presents the T cell with an antigen (which it has taken from a chopped up pathogen)

 

CD40, from the B cell, then binds to its receptor on the T cell, activating the T cell

 

T cell activation causes cytokines to be released, which bind to the original B cell --> causing them to proliferate

6

Why does our immune response struggle with tumours?

As they are mainly 'self' cells, and so are seen as weakly immunogenic

 

There are also few specific oncoproteins or self-antigens that are easy to target (normally hidden)

 

These are normally targeted by Cytotoxic T cells and NK cells

7

What are Somatic Hypermutations?

These are beneficial mutations that occur in amino acid chains, making antibodies more specific, and so better

8

Explain how blood grouping works

Everybody has a basic glycolipid antigen (O)

 

Some people have attatched carbohydrate groups (A or B)

 

These groups produce antibodies against the other types of blood (eg, A produces anti B antibodies)

9

How are Conjugate Polysaccharide vaccines made?

The surface polysaccharide from the pathogen is grown (via fermentation) and isolated

 

The carrier protein is also grown and purified seperately

 

Toxins are then removed from the polysaccharide, before being covalently bonded to the carrier protein

 

Purification and formulation then occurs

10

Describe Type 1 hypersensitivity reactions

Immediate Hypersensitivity

 

This is the stimulation of mast cells via the binding of FcR to IgE specifically

 

This causes increased vascular permeability, vasodialation, smooth muscle contraction and local inflammation

 

This occurs rapidly after antigen exposure

11

What are the first type of cells that respond to an infection?

Neutrophils

12

Describe Type II hypersensitivties

Autoantibodies --> Occurs by 3 possible mechanisms

 

Activates complement and stimulate phagocytosis (eg, haemolytic anaemia)

 

Recruit neutrophiles, which can cause cell damage (eg, glomerular nephritis)

 

Can bind to receptors, which can stimulate or inhibit certain functions (eg, graves disease or myasthenia gravis)

13

What are live (attenuated) vaccines?

These are a weakend version of the real virus/bacteria

 

These must grow to a sufficient level inside the body to trigger the immune response

 

These are cheap and dont need adjuvants

 

But it can sometimes cause a disease to occur!!

14

How are live (attenuated) vaccines made?

The pathogen is passaged many times (eg, in chick embryo eggs) under stress conditions which causes the pathogen to have slower replication, and to lose its virulence factors

 

Purification and formulation then occurs

15

How can B cell activation be downregulated?

By the engagement of an Fc co-receptor

 

This occurs by antibodies returning to its parent B cell, binding to its Fc receptor

 

This switches off the B cell proliferation

16

What is the concept of vaccinology?

Being exposed to a pathogen that does not lead to a disease state

 

But memory cells still being produced

17

What are the 2 forms of T cells?

Helper T Cells (CD4+) - Recongnise fragments on class 2 MHC

Th1 - Activate macrophages and cytotoxic T cells (IFN/TNF)

Th2 - Provides co-stimulatory help to B cells, helping activating them (eg, IL-4/5/10)

 

 

Cytotoxic T Cells (CD8+) - Recognise fragments on class 1 MHC --> This kills the infected cells, and so is best for viral infections

 

 

18

What is a recombinant sub-unit vaccine?

Recombinantly (using other microbes) made vaccines that are made up of one antigenic part of the pathogen, such as proteins or surface polysaccharides

 

 

19

Explain how Antigen Recognition occurs?

T Cell recognise small fragments of antigens that are presented by APCs

 

Peptide fragments bind to the grooves of the MHC

 

The TCR binds to the MHC and peptide residues

 

CD4/8 (dependent on the class of MHC can also bind the MHC, preventing the death of the TCR

20

What is a vaccine adjuvant?

 

And what are the 4 reasons for having them?

They enhance the protection provided by vaccines by promoting rapid, long lasting and broad immunity

 

Stronger and longer immunity

 

Antigen-Sparing --> as less antigens are needed to form an immune response

 

Cross-reactive immunity --> induces a broader immune response

 

To overcome weakened immunity --> eg immunocompromised

21

What are the physical barriers of the innate immune system?

Epithelial cells

 

Can secrete defensins, which act as broad-spectrum antibiotics

 

The secretion of these is increased by the secretion/presence of cytokines

22

What are the 2 types of thymic selection?

Positive Selection - When the T cell doesnt recognise/bind to our test MHCs, so it signalled to die (via apoptosis)

 

Negative Selection - The T cell binds too strongly to the test MHC (activating it) and so is signalled to die (via apoptosis)

23

Explain the differences between the 2 classes of Major Histamine Complexes (MHC)?

Class 1 - These are recognised by CD8+ cells (cytotoxic T cells)

Present on all cells, so define what our 'self is' --> important for transplant patients

 

 

Class 2 - Recognised by CD4+ cells (helper T cells)

 

Only found on antigen presenting cells, like macrophages

 

 

24

When does Autoimmunity occur?

When there is a faliure/breakdown in mechanisms that are normally responsible for maintaining self tolerance

25

What are the 5 classes of antibody/immunoglobulin?

A --> Airborne

D

E --> Allergy

G --> General

M --> Immature

 

26

Describe Type III hypersensitivities

Deposition of immune complexes

 

This is the cross-linking of antibodies, which can cause several responses --> Can block blood vessels as they're so large

 

Normally causes complement activation and FcR -- neutrophil reponses

 

When systemic = Systemic Lupus Erythematosus (SLE)

 

27

What are Conjugate Polysaccharide vaccines?

Polysaccharides from the bacteria are attatched to a carrier protein (which are often toxoids)

 

This is because the polysaccharide itself will not illict a T-cell immune reponse

 

They have high efficacy and safety

28

What are the 5 different types of vaccine?

Live (attenuated)

 

Inactivated

 

Recombinant sub-unit

 

Toxoid

 

Conjugate polysaccharide-protein

29

Can T cell receptors undergo somatic hypermutation?

No

 

So their affinity remains at a constant low level

30

What are the 3 vital functions that a good immune system has?

It has quick recognition

 

Pathogens can be neutralised quickly

 

A good memory can be produced