3. The cellular basis of autoimmunity 2 - other immune cells Flashcards
1
Q
What are CD4 T cells?
A
The key drivers and co-ordinators of autoimmunity
2
Q
What is the study of autoimmunity?
A
the study of immunity
3
Q
What are some genes not involved with T cells and TCRs that are linked to autoimmunity?
A
- type 1 diabetes is associated with IRF7 and the anti-viral response.
- Multiple sclerosis association with TNFSFR1
- Rheumatoid arthritis association with IL6R
4
Q
What does antigen presentation alone induce in T cells?
A
Anergy
5
Q
What does antigen presentation and co-stimulation induce in T cells?
A
Activation
6
Q
What does antigen presentation, co-stimulation and cytokine signalling induce in T cells?
A
Activation and instruction
7
Q
What determines which cytokines are present in the environment?
A
What activates the immune response
8
Q
What do you need for full T cell activation?
A
- Antigen presentation
- Co-stimulation
- Cytokine signalling
9
Q
Can autoreactive T cells cause autoimmunity by themselves?
A
- No (they can in RAG deficient backgrounds)
- Other things limit the development of disease and dampen the autoimmune T cells.
10
Q
Overview of autoimmunity: Initiation
A
- Naive T cells with the potential to recognise autoantigens.
- Molecular mimicry
- Bystander activation
11
Q
Overview of autoimmunity: Expansion
A
Trafficking of immune cells around the body
12
Q
Overview of autoimmunity: Target organ localisation
A
- CD4+ T cells locate that target antigen and organ.
- Local inflammation and tissue damage
- Recruitment of other immune cells.
- Interactions with T and B cells in the draining lymph node.
13
Q
Overview of autoimmunity: Amplification, regulation and generation of memory
A
- Follows the immune response.
- Amplification through things like macrophages.
- Regulation through IL-10 and IL-35.
- Generation of systemic and tissue specific memory.
14
Q
What is the visualisation of EAU?
A
- The primary peak with acute inflammation.
- The secondary regulation with tissue damage and thinning of the retina.
- Using flow cytometry, you can see CD4 T cells accumulate over time in the autoimmune site.
15
Q
Does the CD4+ T cell phenotype affect autoimmune disease progression?
A
- Yes different CD4 phenotypes correlate with different disease and severity.
- Transgenic T cells so that Th17 cells have a more severe clinical phenotype than Th2.
16
Q
What factors can drive CD4+ T cell differentiation?
A
- Signal 1: Genetic factors like cytokines, and costimulation.
- Signal 2: Environment through route of administration, adjuvants and dose.
- Signal 3: cytokine environment and dendritic cell phenotype
17
Q
What are the different phenotypes of CD4 T cells associated with?
A
- Different cytokines that promote their differentiation.
- Different transcription factors that determine gene expression.
- Different chemokine receptors
- Different types of pathogens
18
Q
What CD4+ T cell phenotypes are most associated with autoimmunity?
A
- Th1
- Th17
- There are arguments about the relative importance of these phenotypes.
- Also, ex-Th17 cells
19
Q
What are the important points about CD4 phenotypes?
A
- Differentiation happens after naive T cell activation.
- Some phenotypes have a greater chance of causing organ-specific autoimmunity and they are found in these organs during disease.
20
Q
Are Treg involved in autoimmunity?
A
- They play a big role in organ-specific autoimmunity.
- They clear up after the immune response and reduce inflammation in the local environment to minimise tissue damage.
- When Tregs don’t work well you set up self sustaining autoimmunity.
21
Q
Th1 cells
A
Differentiation cytokine: IL-12
Transcription factors: Stat4 and T-bet
Effector cytokine: IFNy
Chemokine receptors: CXCR3 and CCR5
22
Q
Th17 cells
A
Differentiation cytokine: IL-6, TGFß1 and IL-23
Transcription factors: Stat3 and RORyt
Effector cytokine: IL-17 and IL-22
Chemokine receptors: CCR4 and CCR6
23
Q
Treg cells
A
Differentiation cytokine: IL-2 and TGFß
Transcription factors: Foxp3
Effector cytokine: IL-10 and TGFß
Chemokine receptors: CCR4, CCR6 and CCR7
24
Q
What is the homeostatic role of Treg?
A
- Homeostatic regulation of auto aggression during normal immune response.
- Resolution of subclinical autoimmunity
25
How can you knock out Tregs?
By knocking out Foxp3
26
What Treg deficiencies can lead to autoimmunity?
1. Reduced Treg numbers or function.
2. Inhibition of diversion of Treg function in inflammatory microenvironments.
3. Hyper-functioning effector cell resistant to Tregs
27
How can Tregs be inhibited by the inflammatory environment?
1. IL-2 deficiency (could be due to lots of autoreactive T cells needing IL-2)
2. Loss of Foxp3 (experimental)
28
How can some hyper-functioning effecter cells become resistant to Tregs?
1. Some autoreactive cells can be transiently or permanently resistant to Tregs.
2. It is unclear how this works.
29
What are Tregs critical for?
Maintaining normal immune homeostasis.
30
What are macrophages?
1. Monocyte derived
2. Present in circulation
3. Important in lots of immune responses
4. Non-specific cells recruited to inflammation
31
What is important when looking at macrophages in animal models?
1. Macrophages in mice are more different to human macrophages than mice T cells are to human T cells.
2. This needs to be considered when looking at animal models.
32
Are macrophages common in autoimmune disease?
1. In some EAU models, macrophages make up the majority of the cells.
2. There are lots of macrophages around in autoimmunity
33
What are macrophages also described as?
CD11b+Ly6G- cells
34
How can you tell if a cell type is critical to a disease process like autoimmunity?
You just knock out the cell and see what happens without them.
35
What happens if you remove macrophages from animal models of experimental autoimmune encephalomyelitis?
1. You don’t get clinical disease.
2. This shows they play a critical role in disease.
3. CD4+ T cells aren't enough to cause disease in this case.
36
What is the role of macrophages in T cell responses?
1. They amplify the T cell response.
2. Th1 cells induce a Th1 response, and macrophages can amplify that.
3. The same applies to all CD4 T cell phenotypes.
37
How do macrophages respond to the environment?
1. Through lots of different receptors.
2. IL4 and IL13
3. IFNy
4. TLR4
38
How are macrophages recruited to autoimmunity?
1. CD4+ T cells are activated and express cytokines.
2. These cytokines recruit macrophages.
39
How do macrophages use the cytokines from the environment?
They interpret the cytokines and respond accordingly.
40
What do macrophages in a Th1 environment do?
The CD4 cell sets up the environment and macrophage effector function contributes to disease
1. They produce toxic products in the tissues.
2. NO/ROS
3. TNF and GM-CSF
4. Innate pro-inflammatory cytokines like IL6 and IL1.
41
do macrophages take on a defined phenotype?
1. No
2. There is very limited evidence that macrophages can have a phenotype that can establish disease.
3. They change depending on the environment.
4. If the macrophages is taken out of the environment it looses its phenotype.
42
What is a centre point of inflammation?
TNF
43
What is TNF?
1. Trimeric structure
2. Important superfamily of molecules
3. Can have local and systemic effects.
4. Signalling happens via 2 receptors. TNFR1 and TNFR2.
5. Therapeutic target in lots of autoimmune diseases like uveitis
44
What is the main TNF receptors for pro-inflammatory activities?
TNFR1
45
What does a knock out in TNFR1 cause?
1. A global reduction in autoimmunity.
2. The CD4 cell recruitment is similar.
3. There is a dramatic reduction in macrophages and no release of NO.
4. These cells are resistant to disease.
5. This shows all macrophages that cause inflammation express TNFR1
46
What is GM-CSF?
1. Granulocyte macrophage colony stimulating factor.
2. A cytokine
3. Highly associated with organ-specific autoimmunity esp in the brain
47
What method was used to prove the role of GM-CSF in macrophages?
1. Using floxing genes
2. This manipulates the gene expression in the macrophage.
48
What is floxing genes?
1. Insertion of LoxP sites on either side of the gene of interest.
2. The induce the expression of Cre recombinase.
3. The gene gets looped out and a single LoxP3 site in the genome.
4. The Cre recombinase is put under a cell-specific promoter so it is expressed in the specific desired cell. eg under the CD4 promoter in CD4 cells.
(need to be cautious when papers use these in terms of selectivity and controls)
49
What do floxing gene experiments need?
Lots of controls to establish specificity
50
What cells were used to show the role of GM-CSF in monocytes?
CCR2+ Ly6C (hi) monocytes
51
What did the experiment investigating the role of GM-CSF monocytes and macrophages in autoimmunity show?
1. Dangerous monocytes and macrophages express Ccr2 and Csf2rb.
2. They amplify the local environment and cause autoimmune disease.
3. Macrophages have lots of receptors for cytokines in the environment.
4. The interpretation of these cytokines determines the amount of damage the cell can do.
52
How did the experiment investigating the role of GM-CSF monocytes and macrophages in autoimmunity use floxing genes?
1. They measured the rates of EAE using clinical scores.
2. They used Cre to remove Csf2rb which is the GM-CSF receptor so the cells can't respond to GM-CSF.
3. They used Ccr2-creER promoter.
4. EAE can be induced by immunisation
4. The group that lacks Csf2rb are resistant to developing EAE.
53
What is the Ccr2-creER promoter?
1. Ccr2 promoter that induces Cre expression that has been modified further.
2. It also has an oestrogen response element so it is only turned on in the presence of tamoxifen.
3. This gives more specificity that means Cre is only expressed in cells that have been treated with tamoxifen.
4. This means Cre expression and Csf2-rb expression can be controlled.
54
Are macrophages and monocytes the only cells that can amplify the inflammatory response?
no other cells can
55
What is the only exception to antibodies not being about to transfer autoimmune disease?
The animals for arthritis K/BxN
56
How was the arthritic model K/BxN developed?
1. Transgenic T cells dependent development of high affinity autoantibodies that can induce arthritis.
2. The autoantibodies alone can induce chronic arthritis.
3. BUT Th17 cells are essential to establish and develop disease.
4. The antibodies could only sustain disease.
5. The Th17 cells were activated by gut resident filamentous bacteria.
57
When are B cells good APCs?
1. They are good APCs for the antigen they are specific for.
2. They are not good at presenting other antigens.
3. B cells present their specific antigen to relevant T cells. This antigen presentation is very efficient.
58
What are the main APCs?
Dendritic cells
59
How did an experiment show B cell can play a role in breaking tolerance?
1. When human cytochrome C is immunised into mice, there are high T cell levels to human CytC and the mice are tolerant of mice CytC.
2. When mouse cytochrome C is immunised into mice, there is no immune response to human or mouse CytC.
3. When a mix of both Human and mouse CytC are immunised into mice, there is an immune response to both CytCs.
4. This is because antibodies produced to human CytC are cross reactive to mouse CytC and the focused antigen presentation of mouse CytC is enough to break tolerance and activate the autoreactive T cells.
60
What interactions do T cells and B cells have in autoimmunity?
1. Stimulation of pathogenic autoantibodies.
2. B cells can expand pathogenic T cells
61
Are B cells essential for the induction of autoimmunity in EAE?
No. B cells are not always involved in the development of autoimmune disease.
62
How were BCR knockouts used to show the role of B cells in autoimmune disease (EAE)?
1. With or without B cells the mice developed EAE.
2. However, the BCR knockouts developed more severe disease that didn’t resolve.
3. This shows that B cells have regulatory functions.
63
What regulatory functions do B cells have on T cells?
1. Secretion of IL-10 and IL-35.
2. Aid the conversion of CD4 T cells to Tregs
64
What is the role of CD8 T cells in autoimmunity?
1. CD8 T cells are generally not important in autoimmunity.
2. However, they are critical for the development of diabetes in NOD mice. CD8 T cells do enough tissue damage to initiate the immune response.
3. CD8 T cells can turn into local resident phenotypes that take on stem cell like properties that provides a constant source of ongoing autoimmunity
65
What is the critical stage of inducing autoimmunity and the cells involved?
1. CD4 cells and APCs
2. The CD4 T cells recognise the self-antigens and cause disease. However, they don’t do anything until the APCs present the antigen to them and activate them.
66
What CD4 phenotypes are involved in Autoimmunity?
Good phenotypes: Tregs that regulate and dampen immunity
Bad phenotypes: Th1 and Th17 that are pro-inflammatory
67
What types of APCs are involved in autoimmunity?
1. Dendritic cells as APCs.
2. Macrophages/ monocytes and neutrophils can be important in amplifying disease
3. Myeloid-derived suppressor cells suppress local immune responses, which can be beneficial.
68
What roles can B cells have in autoimmunity?
1. Promotion of disease
2. Prevention of disease
69
A model progression of autoimmunity with the different cells
Inducing disease:
1. Naive T cells are activated in the draining lymph node
2. Activated T cells localised in the target organ
3. Slow accumulation of CD11b+ APCs
Primary peak:
1. Ly6G+ neutrophil peak
2. Rapid accumulation of CD4+ and CD11b+ cells
Secondary regulation:
Presence of CD4+, CD11b+, CD8+ cells, NK cells and B cells
70
What inflammatory mediators could be potential treatment strategies for autoimmunity?
1. TNF
2. NOS2
3. IFNy
4, IL-17
71
Is TNF a good therapeutic target for autoimmunity?
1. Yes
2. It is widely used in clinic for arthritis, uveitis and crohn's disease.
3. However it can make MS worse.
72
Is NOS2 a good therapeutic target for autoimmunity?
1. No
2. It makes EAE and EAU worse
73
Is IFNy a good therapeutic target for autoimmunity?
1. No
2. It makes disease worse as ti produces important negative feedback signals
74
Is IL-17 a good therapeutic target for autoimmunity?
1. Yes
2. It is an effective treatment for psoriasis
75
Is targeting cell trafficking a good therapeutic target for autoimmunity?
1. Lots of Molecules are important for moving cells around the body and disease process.
2. These can be targeted and work well in serious diseases like MS.
3. BUT they can have serious non-specific adverse effects that can be difficult to live with.
4. They cause reduced immunosurveillance which could cause the reactivation of viruses in the brain.
76
Are different cell types good therapeutic targets for autoimmunity?
1. Macrophage blocking shows reduced disease in mice.
2. Blocking NK cells exacerbate disease like EAE but reduce EAU.
3. Blocking T cells is effective in MS trials in mice and humans.
4. Blocking B cells is effective in several autoimmune conditions
77
How can B cells be blocked to treat autoimmunity?
1. Anti-CD20 treatment.
2. This is the therapy of choice for MS and in trials for diabetes and uveitis.
78
What is CAR T cell therapy?
1. An Anti-CD19 therapy developed for B cell leukaemia.
2. It can be applied to serious autoimmune diseases like SLE, systemic sclerosis and connective tissue disorders.
3. Currently in small trials or experiments.
4. Very expensive due to T cell manipulation.
5. Currently reported in a very rosy way. It needs time to see side effects and if this is as good as it seems
79
What is most treatment of autoimmunity complicated by?
Rare and severe adverse outcomes
