Lectures 16-18 Flashcards
(122 cards)
1
Q
Provide three functions of the immune system.
A
Prevent entry of (or eliminate) infectious agents/pathogens
Minimise damage that pathogens may cause
Ensure infection is short-lived and leaves no permanent damage.
2
Q
What two basic processes occur in immune responses?
A
Recognition of the pathogen.
Reaction to eliminate the pathogen.
3
Q
What are the two types of immune responses?
A
Innate or adaptive.
4
Q
Give an overview of innate immunity.
A
First line of defence
Non-specific and rapid, same response on each encounter with an antigen.
Innate immune response systems include:
- External barriers (e.g., skin or mucous membranes).
- Receptors that recognise a broad spectrum of pathogens.
5
Q
Give an overview of adaptive immunity.
A
It’s acquired immunity based on creating an immunological memory.
It’s pathogen specific (e.g., measles, after infection you have life long immunity).
Works on the formation of antibodies in response to antigens.
Basis of vaccinations.
6
Q
Name 8 cells specific to the innate immune response.
A
Innate Immunity (Rapid Response):
1. Macrophage
2. Dendritic Cell
3. Mast Cell
4. Natural Killer Cell
5. Complement Proteins
6. Neutrophil
7. Eosinophil.
8. Basophil
7
Q
Name 4 cells that are specific to adaptive immune response. Give a brief description of them too.
A
Adaptive Immunity (Slow Response):
1. B Cell: Lymphocytes that produce antibodies specific to antigens; also function as antigen-presenting cells and form memory cells for long-term immunity.
2. T Cell: Lymphocytes with various roles in adaptive immunity, subdivided into:
- CD4+ (Helper T Cell): Coordinate immune responses by activating B cells and other immune cells.
- CD8+ (Cytotoxic T Cell): Kill infected or cancerous cells by recognizing antigens presented on MHC class I molecules.
3. γδ T Cell: A less common type of T cell with innate and adaptive immune features; they respond to non-peptide antigens and play a role in tissue surveillance.
4. Natural Killer T Cell: Hybrid cells that share characteristics of both innate NK cells and adaptive T cells; they recognize lipid antigens presented by CD1d molecules and can quickly respond to pathogens.
8
Q
Name two cells that overlap both the innate and adaptive immune responses. Give a brief description of them too.
A
- Dendritic Cells: Serve as a bridge by presenting antigens to T cells, initiating adaptive immunity.
- Natural Killer T Cells: Exhibit characteristics of both systems, with rapid response and antigen specificity.
9
Q
What are Macrophages?
A
Large phagocytic cells that engulf and digest pathogens, debris, and dead cells; also release cytokines to recruit other immune cells.
10
Q
What are Dendritic cells?
A
Specialised antigen-presenting cells that capture antigens and present them to T cells, bridging innate and adaptive immunity.
11
Q
What are Mast cells?
A
Involved in allergic reactions and inflammation; release histamine and other chemicals to recruit immune cells to the infection site.
12
Q
What are Natural killer cells?
A
Lymphocytes that destroy infected or cancerous cells by inducing apoptosis without the need for prior activation.
13
Q
What are Complement proteins?
A
A group of proteins that enhance the ability of antibodies and phagocytic cells to clear pathogens through a cascade of reactions.
14
Q
What are Neutrophils?
A
Highly abundant phagocytic cells that are the first responders to infection, ingesting and killing microbes.
15
Q
What are Eosinophils?
A
Granulocytes that combat multicellular parasites (e.g., helminths) and are involved in allergic reactions.
16
Q
What are Basophils?
A
Granulocytes that release histamine and other chemicals during allergic and inflammatory responses.
17
Q
What are B cells?
A
Lymphocytes that produce antibodies specific to antigens; also function as antigen-presenting cells and form memory cells for long-term immunity.
18
Q
What are T cells?
A
Lymphocytes with various roles in adaptive immunity, subdivided into:
CD4+ and CD8+ cells
19
Q
What are CD4+ cells? (Helper T cell)
A
Coordinate immune responses by activating B cells and other immune cells.
20
Q
What are CD8+ cells? (Cytotoxic T cell)
A
Kill infected or cancerous cells by recognising antigens presented on MHC class I molecules.
21
Q
What are γδ T cells?
A
A less common type of T cell with innate and adaptive immune features; they respond to non-peptide antigens and play a role in tissue surveillance.
22
Q
What are Natural killer T cells?
A
Hybrid cells that share characteristics of both innate NK cells and adaptive T cells; they recognise lipid antigens presented by CD1d molecules and can quickly respond to pathogens.
23
Q
Outline the types of cells in the immune systems that have circadian clocks.
A
Numerous different immune cells have been demonstrated to possess clockwork machinery.
Circulating immune, Tissue resident cells, ILCs and CD8+ T cells.
24
Q
What are APCs?
A
Antigen Presenting Cells
25
When was the first evidence of intrinsic clocks in macrophages found? Where were they?
2009 and they were peritoneal
26
Outline the Keller et al (2009) study into Per2 and Rev-erba rhythms in mice macrophages.
METHODS:
- Used Per2::Luc reporter mice.
- Took the spleen, lymph nodes and macrophages.
- Put them under photon multiplier tubes to measure bioluminescence over time.
- Used qPCR to look at two genes, Per2 and Reverba
RESULTS:
- 24 hour rhythms were shown.
- The oscillations in the macrophages were in antiphase with each other.
27
Outline the Kelly et al (2009) study into the influence of clock timing on EX VIVO macrophage activity.
METHODS:
- Cultured macrophages from the spleen and introduced lipopolysaccharide.
- When macrophages detect this, they produce cytokines.
- 4 hours later they used ELISA to quantify TNF alpha response.
- Repeated this every 4 hours over 72 hours.
RESULTS:
- There is NOT a consistent response across time; there is a higher response at some points and lower at others.
Thus, a macrophage intrinsic clockwork regulates circadian TNF-alpha secretion upon LPS stimulation.
28
Outline the Kelly et al (2009) study into the influence of clock timing on IN VIVO macrophage activity.
METHODS:
- Took a live mouse and injected LPS into the peritoneal cavity and 4 hours later used ELISA to quantify cytokine responses.
- Changed the time of day that LPS was injected and measured the differences.
RESULTS:
- Found that at CT12, active phase, there were higher levels of cytokine response compared to CT0.
Thus, time of day does impact the innate response of macrophages in vivo.
29
Outline the Gibbs et al (2012) study into the role of the macrophage clock in vivo.
**METHODS:**
- Used Cre-Lox system to delete BMAL1 in LysM expressing cells.
- This was targeting strategy to remove it from macrophages (as it has LysM).
- Used PER2::Luc reporter to track rhythms in WT vs LysM-BMAL1-/- over 10 days.
- Introduced Lipopolysaccharides (LPS) to induce an inflammatory response from the macrophages - measured the IL-6 as a result.
**RESULTS:**
- WT there is still BMAL and KO there was no BMAL (method worked).
- Macrophages without BMAL1 were arrhythmic.
- In WT, there was diurnal variation and higher responses to LPS at CT12 than CT0.
- In LysM-BMAL1-/- KO, there was a loss of temporal gating of immune response; there was no significant difference between CT0 and CT12.
Thus the circadian clock regulates in vivo responses in macrophages.
30
Outline the Gibbs et al (2012) study into REV-ERB alpha and its role in clock and immunity.
METHODS:
- Took WT and LysM-BMAL1-/- mice.
- Compared levels of PER2, BMAL1, CRY1 REV-ERB alpha, REV-ERB beta and DBP.
- Then compared cytokine levels (IL-6) in response to LPS between WT and REV-ERBalpha-/- at CT0 and CT12.
RESULTS:
**Levels of Clock Gene Expression in BMAL1-/-**:
- BMAL1 KO leads to a reduction in rev-erb alpha and rev-erb beta expression.
- This indicates that REV-ERB alpha’s activity is disrupted when BMAL1 is absent.
- The rhythmic expression (temporal gating) of other clock genes (e.g., per2, cry1) and immune-related genes is also altered.
**REV-ERBalpha-/-**:
- In REV-ERBalpha-/- you lost the temporal gating, in WT it is present, showing that REV-ERB is critical for time dependent regulation of inflammatory responses.
THUS, this shows that REV-ERB is a key link between the clock and immunity.
31
What is the NLRP3 inflammasome a critical component of?
Innate Immune System.
32
What is the two-step activation process of NLRP3 inflammasome?
1. Primed by pro-inflammatory stimuli (e.g., LPS).
2. Secondary ignals (danger associated molecular pattern, DAMPs) trigger further activation.
33
What does activation of the NLRP3 inflammasome elicit?
Maturation of IL1Beta and IL18.
34
In what manner is NLRP3 expressed and what controls it?
A diurnal manner under the control of REV-ERBalpha.
35
What did Chromatin Immunoprecipitation (ChIP) reveal about REV-ERB-alpha and NLRP3?
That REV-ERBalpha can directly bind to NLRP3 promoter region.
36
Outline the Findings of the Pourcet et al (2018) study into REV-ERBalpha and the NLRP3 inflammasome.
This work showed that REVEVB alpha regulated the NLRP3 inflammasome, which is a critical component of the immune response.
In WT mice, the NLRP3 transcriptome peaks in the dark phase.
In the KO condition, you lose the peak expression of NLRP3.
Thus REV-ERB is regulating it's expression via direct binding to the NLRP3 promoter.
Assays shows it can directly bind.
37
Outline the Pourcet et al (2018) study into Fulminant hepatitis.
METHODS:
- Animals were given the trigger for Fulminant hepatitis and then treated at different circadian times ranging from day time to night time.
RESULTS:
- There is a variation in response depending on the time of day of treatment.
- Treated at night means more likely to survive.
- Worse outcome if treated during the day.
Response was mediated by REV-ERB alpha.
38
Describe the basic jet-lag protocol in mice.
6h phase advance once per week (by shortening the dark period).
Equivalent to flying from Chicago to Manchester every week.
39
Describe the Castanon-Cervantes et al (2010) study into the effects of 'Jet Lag' on macrophage function.
METHODS:
- Implement a jet lag protocol in which there is one 6h phase advance per week (6h reduction in dark phase).
- Compare pro-inflammatory response by peritoneal macrophages to LPS challenge vs controls.
RESULTS:
- Circadian disruption worsens outcomes.
- There was an increased pro-inflammatory response in the peritoneal macrophages across all cytokines.
40
Describe monocytes.
Monocytes are versatile immune cells that act as first responders to infections and tissue damage.
They bridge the innate and adaptive immune systems by removing harmful materials, producing inflammatory signals and differentiating into macrophages and dendritic cells.
Their role is essential in both fighting infections and maintaining immune balance.
41
What is the role mast cells.
| 5
Mast cells release histamine and other chemicals to:
* Mediate allergic reactions
* Defend against pathogens
* Regulate blood flow
* Promote wound healing
* Recruit immune cells during inflammation.
42
What is the relation between the clock and monocytes? (Nguyen et al., 2013)
The clock within monocytes can impact how they traffic to sites of inflammation.
43
What is the relation between the clock and mast cells? (Nakamura et al., 2017).
They have a robust clock so if you KO the clock there is no longer a time of day gating of histamine release.
44
Summarise the 4 main points regarding clocks and immunity.
1. Clocks within innate immune cells influence the amplitude of the cellular response to a challenge.
2. Clocks influence whole animal responses to acute pathogenic challenge.
3. In general, deletion or disruption of the clock negatively impacts how a cell responds to an inflammatory stimulus.
4. REV-ERB alpha directly regulates inflammatory mechanisms independent of clockwork machinery.
45
Where are T cells and B cells derived from?
Haematopoietic stem cells in the bone marrow.
46
Where do B cells mature?
In the bone marrow.
47
Where do T cells mature?
In the thymus.
48
What differentiates CD4+ cells into subsets?
Transcription factors.
49
What are the 5 subsets of CD4+ cells?
Th1
Th2
Th17
Th9
iTreg
50
What do Th17 cells protect against and produce?
Bacterial and fungal infection and produce interleukin 17 (IL17).
51
What specifically drives the lineage specification of Th17 cells?
RORy(gamma)t
52
What is the relationship between REV-ERBalpha and RORyt?
REV-ERbalpha antagonises RORyt.
Over expression of REV-ERBAlpha...
- Inhibits RORyt driven Th17 cell differentiation.
- Inhibits transcription of Th17 signature genes.
53
Briefly explain CD4+ cell differentiation.
In order for the CD4+ cells to differentiate, they need to express lineage specific transcription factors.
E.g., to become a iTreg a CD4+ needs to express FoxP3.
Within the right environment of the TGFbeta and IL-2 it will become a iTreg.
54
What is the difference between the intrinsic oscillators of adaptive and innate immune cells?
Adaptive immune cells show less robust intrinsic oscillators than innate immune cells.
55
What are two pieces of conflicting evidence for a functional clock within CD4+ T Cells?
Druzd et al (2017):
- *Lymphocyte circadian clocks control lymph node trafficking and adaptive immune responses*
Hemmers and Rudensky (2015).
- *The cell-intrinsic circadian clock is dispensable for lymphocyte differentiation and function.
56
Outline the circadian control of lymphocyte trafficking.
Their behaviour is VERY rhythmic.
Lymphocyte trafficking across the body is shown to be under Clock control.
They travel across the body surveying antigens via the blood, lymph nodes and lymph.
If they DO detect something, they can go back to the lymphocytes and elicit a response.
*There is a peak in lymphocytes at the lymph nodes at ~CT12 (Druzd et al, 2017).
57
What drives rhythms in lymphocyte trafficking?
Combination of cell intrinsic clocks and rhythmic extrinsic cues.
58
Name the two transcription factors that drive rhythmic lymphocyte homing to and egress from lymph nodes.
Ccr7 and S1pr1
59
What does the CCR7 chemokine receptor promote?
Lymphocyte homing to lymph nodes.
60
What does S1PR1 stand for?
Sphingosine-1-phosphate receptor 1
61
What does S1PR1 do in regards to lymphocytes?
It is a receptor that recognises S1P and drives lymphocyte egress.
62
Outline the findings of the Druzd et al (2017) study into BMAL1-/- effect on rhythmic T cell trafficking.
If you delete BMAL1 from T cell, you can prevent rhythmic trafficking behaviour.
Controls showed a peak at ZT13 in T cell trafficking but in BMAL1-/- there is no significant peak.
CCR7 is expressed by T cells and is a chemokine receptor.
When it's peaking, lymphocytes will traffic back to lymph nodes.
S1PR1 does the opposite AND in antiphase to CCR7.
Balance between these signals drives the trafficking.
63
How do cell intrinsic clocks drive rhythmic lymphocyte trafficking?
DAY:
- Higher S1PR1 expression -> induced lymphocyte egress (leaving).
NIGHT:
- Higher CCR7 expression -> increased lymphocyte homing (returning).
64
Provide an overview of glucocorticoids.
Cortisol (humans) corticosterone (rodents).
Released from the adrenal via the hypothalamic-pituitary-adrenal (HPA) axis.
Release is pulsatile.
Glucocorticoid levels peak at the start of the active phase (day for humans, night for rodents).
Thus VERY circadian.
65
Detail how glucocorticoids act as an extrinsic signal in adaptive immunity.
They drive the expression of CXCR4 (a cell surface chemokine receptor) on CD4+ ad CD8+ T cells.
66
What is CXCR4 critical for?
T cell homing to lymph nodes.
67
Outline the oscillations of CXCR4 from day to night.
DAY:
Low levels of CXCR4
NIGHT:
High levels of CXCR4
68
What does T cell specific deletion of glucocorticoid receptor (GR) do?
It abolishes the variation in CXCR4 expression as they can't sense the presence of glucocorticoids, which drive this expression.
69
Provide an overview of adrenergic signals as a rhythmic immune cell extrinsic signal.
Adrenergic nerves control immune cell trafficking as Lymphocytes express Beta2-adrenergic receptor.
Activation of B2AR enhances the responsiveness of chemokine receptors (CXCR4 and CCR7) and inhibits egress from LNs.
Adrenergic nerves release noradrenaline in a circadian manner and directly innervate lymphoid organs, their signals contributing to diurnal rhythmicity of lymphocyte trafficking.
70
Summarise Lymphocyte trafficking in relation to circadian rhythms.
Lymphocyte trafficking is critical for detecting pathogens.
Lymphocyte homing to lymph nodes is highest at the start of the active phase.
Trafficking is regulated by diurnal variation in expression and activity of chemokine receptors and signalling molecules on lymphocytes.
This diurnal variation is controlled through a combination of cell intrinsic clocks and responses to rhythmic extrinsic signals.
Adaptive immunity response to systemic rhythmic cues.
71
Define vaccination.
Administration of antigenic material to stimulate the immune system to develop adaptive immunity to pathogen.
72
Detail the 7 steps of how vaccinations work.
Vaccine injected into muscle.
Protein antigen taken up by dendritic cells, which are activated by danger signals in the adjuvant.
Dendritic cells traffic to draining lymph odes.
Here, they present peptides to T cells and B cells.
T cells drive B cell development.
B cells produce antibody response.
Memory B cells produced with mediate immune memory.
73
Outline the Long et al (2016) study into the time of day responses to vaccination to influenza.
METHODS:
- 298 participants (age 65 years+)
- Non-blinded cluster randomised trial.
- VISIT 1: blood test and flu vaccine at either 9-11am or 3-5pm.
- VISIT 2: one month later, blood test.
- Blood analysed for antibody titer.
RESULTS:
- Those who came in morning had a higher level of antibody titer and thus an enhanced response.
74
Outline the Danino et al (2024) study into the time of day responses to vaccination to varicella.
METHODS:
- 251,141 children <6 years old.
- Time of first dose of varicella immunisation
- Compared break through infection after immunisation in:
- Morning (7:00 - 10:59)
- Afternoon (11:00 - 15:59)
- Evening (16:00 - 19:59)
RESULTS:
- Evening group had highest rates of breakthrough infection.
- Therefore, morning/afternoon were more effective.
(Chickenpox).
75
What are the overall findings about vaccination timing and efficacy?
Morning vaccination generally more effective than afternoon.
76
Outline the Ruiz et al (2020) study into night shift work and immune response to meningococcal vaccines.
METHODS:
- 34 shift workers, split 50:50 between nocturnal shifts and diurnal shifts.
- Meningococcal C Meningitis Vaccine.
- Assessed humoral and cellular responses.
RESULTS:
- Night shift workers showed weaker specific humoral response to vaccination.
- Sufficient sleep time and rhythm synchronisation important for the development of antigen specific immune response.
77
What is the basic relationship between circadian rhythms and chronic **inflammatory** diseases?
Give 4 examples.
They show circadian variation; patients often report symptoms being worse at a certain time of day.
- Nocturnal Asthma
- Morning-Joint Stiffness in Arthritis
- Inflammatory Bowel Disease
- Psoriasis Itches Worse in the Evening.
78
Provide an overview of Rheumatoid Arthritis.
Debilitating autoimmune condition.
Inflammation and swelling in the joints.
Tissue remodelling and disability.
Inflammation driven by resident joint synovial cells and infiltrating immune cells.
79
What is the relationship between circadian rhythms and Rheumatoid Arthritis?
Patients report increased joint stiffness in the early morning 5-9am.
And there are higher levels of pro-inflammatory cytokines (e.g., Interleukin 6, IL6) detected in blood during the morning.
80
Outline the Downtown et al (2022) study into inflammatory RA in mice.
METHODS:
- Used Mouse Model- Collagen Induced Arthritis
- This is the mouse version of inflammatory arthritis.
- Tested the levels of pro-inflammatory cytokines throughout the day.
RESULTS:
- Higher levels of IL-6, IL1beta, CCL1 etc in the morning.
- Shows that we can induce this condition in nocturnal rodents too.
81
Outline the findings of the Hand et al (2020) study into circadian variation in RA.
There are increased numbers of anti-inflammatory regulatory T cells in inflamed joints at night - repressing cytokine production by other cells.
And there is a transition to a more anti-inflammatory environment with affected joints during the active phase.
82
Briefly describe asthma.
It's a chronic inflammatory disorder of the airways which leads to narrowing; patients suffer from episodes of wheezing, breathlessness, chest tightness and coughing.
83
What is nocturnal asthma?
It's the exacerbation of asthma at night, peaking at around 4:00am.
Increased symptoms and need for medication at night.
Can lead to sudden death from asthma.
84
What has been shown about lung function and circadian variation?
Lung function is measured by spirometry, for example, Forced Expiratory Volume in 1 second (FEV1) which is the volume of air that can be forced out in 1 second after a deep breath.
Lung function fluctuates over 24h in healthy individuals.
This day-night variation becomes more pronounced in asthmatics (time of heightened symptoms coincides with increase airway narrowing at 4:00am).
85
What is the relationship between eosinophils and asthma?
In asthma, eosinophils contribute to initiation and maintenance of inflammation.
Eosinophil numbers are used in the clinic as a marker of disease severity.
Eosinophils circulating in the blood migrate to the lung in response to chemokine signals (E.g., eotaxin).
Then, these eosinophils cause inflammation and tissue damage.
86
Outline the findings of the Durrington et al (018) study into diurnal variation in eosinophil numbers in asthmatics.
In individuals with asthma, sputum eotaxin (a chemokine associated with eosinophil recruitment) levels are observed to be twice as high at 04:00 compared to 16:00.
The numbers of eosinophils in sputum also peak at 04:00.
This variation suggests a rhythmic recruitment of eosinophils to the inflamed lung, potentially influenced by circadian mechanisms.
87
What is the implication for asthmatic therapy of finding a circadian rhythm in sputum eosinophils?
Finding an increase in sputum eosinophils is a red flag for adjusting therapy; if there are >3% then it results in treatment escalation.
This occurs higher at morning clinic sessions due to the circadian variation, therefore, leading to more increases in medication happening in morning clinics.
By standardising the time of collection to the afternoon, it will likely reduced the amount of people having treatment escalation.
88
What were the findings of the Maidstone et al (2021) study into circadian disruption and inflammatory disease?
Shift work causes misalignment between internal circadian time and the external light:dark cycle.
Approximately 20% of the working population work permanent or rotating shifts.
The odds ratio between about of night shift work and severe asthma increase as you do more night shifts.
89
What are the two main branches of chronotherapy?
Timed application of existing therapies.
Use of novel therapies which target the clock.
90
What has been shown between protein coding genes and circadian rhythms?
43% of all protein coding genes show circadian rhythms in transcription somewhere in the body.
91
Why is chronotherapy important?
Drug targets oscillate.
De-toxification pathways and efflux mechanisms are under clock controls.
There are oscillations in off-target pathways.
Therefore, chronotherapy works to maximise efficacy, reduce doses needed and reduce adverse effects.
92
Why is it relevant to chronotherapy that there are oscillations in off-target pathways?
Because if there are off target effects that would negatively effect metabolic pathways, you could potentially time it to reduce off target effects.
93
Outline the details of Simvastatin and their relation to circadian rhythms.
It's a statin prescribed for prevention of coronary artery disease.
Acts by inhibiting the enzyme HMG CoA reductase which controls synthesis of cholesterol in the liver.
Physiological studies show the most cholesterol is synthesised when dietary intake is at its lowest (e.g. night),
Thus there is a rational for taking statins at night.
94
Outline the findings of the Wallace et al (2003) study into Simvastatin.
METHODS:
- Used a randomised trial...
RESULTS:
- Switching time of simvastatin dosing from the evening to morning resulted in significant increase in total and low density lipoprotein cholesterol.
- Probably best taken at night.
- Widely prescribed statin so findings are far reaching.
- Other statins (atorvastatin) efficacy are not affected by time of day, perhaps due to a longer elimination half life?
95
Outline Prednisone and it's relation to CAPRA 1.
CAPRA 1 = the Circadian Administration of Prednisone in Rheumatoid Arthritis study.
Used Prednisone which is an anti-inflammatory glucocorticoid.
Gave it a modified release system.
- Tablet that releases prednisone 4h after ingestion.
- Take at "bedtime" release at 02:00.
It allows adaptation of timing of drug release to symptoms of disease.
96
Outline the CAPRA 1 Study.
CAPRA 1 = the Circadian Administration of Prednisone in Rheumatoid Arthritis study.
METHODS:
- Males and Females (age 18-80).
- All have active rheumatoid arthritis
- Was a multi-centre, randomised, double-blind study.
- Participants received same active drug, delivered at either 02:00 (delayed release) or 06:00 (immediate release).
RESULTS:
- Delayed release resulted in improvement in morning joint stiffness (self reported).
- Circulating interleukin 6 levels were lower with delayed release.
- No other clinically relevant differences.
*This was the first clinical evidence of effectiveness of chronotherapy in treatment of inflammatory disease.
97
What is the goal of chronotherapy in cancer immunotherapy?
Chronotherapy in cancer immunotherapy aims to increase remission rates in cancer patients by leveraging the immune system to fight cancer.
98
What are the 4 key methods used in cancer immunotherapy to fight cancer?
Monoclonal antibodies
Checkpoint inhibitors
Immune system modulators
CAR-T therapy
99
What are checkpoint inhibitors and how do they work?
Checkpoint inhibitors (e.g., anti-PD-1/anti-PD-L1) target T cells and block signals from cancer cells that would "switch off" the T cells, allowing the immune system to fight the tumour effectively.
100
What is the mechanism of action for PD-L1 and PD-1 checkpoint inhibitors?
PD-L1 on tumour cells binds to PD-1 on T cells, deactivating them.
Checkpoint inhibitors block this interaction, restoring T cell activity against the tumour.
101
Outline the Wang et al (2024) study into chronotherapy in cancer immunotherapy.
**METHODS:**
- Used a melanoma mouse model.
- Measured the daily variation in numbers of tumour infiltrating CD4+ and CD8+ T cells - regulated by preferential migration of T cells to tumours at certain times of day.
**RESULTS:**
- Within the tumour, T cells are more anti-tumourgenic in the evening and expresses less PD-1.
- Time of day administration of anti PD-1 antibodies impacts tumour growth, with less growth when therapy was performed in the evening compared with the morning.
Thus, the timing of the administration of checkpoint inhibitors could be manipulated to make them more effective.
102
What did a meta-analysis by Landre et al. (2024) show about the outcome of immunotherapy in cancers according to the time of administration?
It showed consistent effects of Time of Day.
Longer survival of patients receiving treatment (in particular 1st treatment) in early part of the day compared to later.
103
Give 4 targets of the circadian clock in which pharmaceuticals that target these are aiming for.
Cryptochrome (CRY)
CK1epsilon
REV-ERB
ROR
104
What is the rationale for wanting to create drugs that target the circadian clock?
The circadian clock regulates many pathways associated with pharmacological treatment of disease.
Mice lacking core components of the circadian clock show inflammatory and metabolic phenotypes.
For example, REV-ERBalpha knockout mice:
- Have increased inflammatory response to stimulation.
- Altered metabolic state.
Therefore there is potential for it to be a therapeutic target for metabolic and inflammatory disease.
105
What is SR9009?
It's a REV-ERBalpha agonist.
Many papers have shown that using this agonist can have benefits in the pathologies/conditions.
E.g., Psoriatic dermatitis, Rheumatoid arthritis, Alzheimer's, Colitis etc.
106
What is EAE?
Experimental Autoimmune Encephalitis - a mouse model of multiple sclerosis.
107
Outline the Chang et al (2019) study into REV-ERB alpha, TH17 and EAE.
**METHODS:**
- Used the Experimental Autoimmune Encephalitis (EAE) mouse model of multiple sclerosis (MS).
- Provide treatment on 7th day with SR9009 (REV-ERB agonist as it antaganonises the pathway that causes inflammation).
- Compared this to the treatment of JUST the vehicle alone.
- Done over a 30 day period.
**RESULTS:**
- After day 10 of being infected, there was a large increase inflammation.
- Those given SR9009 pre-inflammation developed **less** of the disease.
- Found less Th17 cells in those who were treated; thought to stop the Th17 cells developing and stopping inflammation.
-----
Showed that treatment with REV-ERB agonist (SR9009) delays the onset and impedes the progression of EAE.
Thus, targeting component of the clock can have a big effect in disease models.
108
What are some issues of using chronotherapy drugs that target the clock in humans?
All data to date is in vitro or in mouse models.
What is the specificity of them?
What is the bioavailability of them?
What are the effects on the central clock and other biological rhythms?
109
What is the Biobank?
A very large scale longitudinal study of 500,000 participants.
It combines in-depth genetic, biological and health related data with subjective and objectively measured data on lifestyle and occupational factors including data on light exposure, chronotype and sleep.
110
Give a brief overview of the Lane et al (2016) study into chronotype and genetic loci.
Looked at genetic loci associated with different chronotypes.
Looking at polymorphisms in genes that associate with later/early wakers.
Per2 is in there, FBXL13 too.
Interesting that there are OTHER genes that aren't explicitly involved in circadian clock.
Thus, likely a lot of genetic factors that determine chronotype.
111
Give a brief overview of the Dashti et al (2019) study into sleep duration and genetic loci.
Looked at sleep duration and genetic loci.
Per1 was involved and so were many, many more genes involved.
There are complex genetic factors effecting chronotype AND sleep duration.
Thus, they likely all interact in complex ways.
112
What have circadian biologist found about the impact of twice yearly clock changes?
Study from UK Biobank and looked at what happened to peoples sleep in reaction to clock changes.
CLOCKS GO BACK:
- Saturday Night/Sunday Morning when clock goes back.
- Get about 30 more minutes of sleep which is likely due to interaction between the clock and the homeostat.
- During the following week they are getting slightly more sleep and then less on the weekends because there is less sleep debt.
CLOCKS GO FORWARD:
- People DEFINITELY lose about an hours sleep and they DON'T catch up initially.
- They go into their work week sleep deprived and begin to catch up and the end of the week.
- This is suboptimal.
Thus, Circadian Scientists suggest that we do not change the time from standard time.
113
Describe the Burns et al (2021) study into the time spent in outdoor light, chronotype etc and its effect on mood.
A study from the biobank.
They looked at the time in outdoor light, chronotype etc and its effect on mood.
The median time spent outdoors was about 2.5 hours.
They are older people too 40-70 range - not reflective of the demographics of the country (more affluent/likely to be white etc).
For every extra hour spent outdoors, the less chance of having a late chronotype.
Getting outdoors for longer is good for your mood.
114
Describe the procedure of the Burns et al (2021) study into the time spent in outdoor light, chronotype etc and its effect on mood.
This study tracked light exposure using a detector on a lanyard.
Tested through different seasons.
Tracked outdoor light on trees as well.
This allowed them to see the difference between real outdoor light and indoor.
Even during the winter there is 100x more light outside than inside.
Outdoors there is a clear seasonal pattern but in personal light exposure there is very little difference.
In this study, they also measured skin temp on wrist as a marker of circadian rhythms.
Wrist skin temperature is different to normal body temp - it's colder in the morning and warmer at night.
They related the maximal skin temp with the light they had beforehand.
Those who got more light in the morning had an earlier skin temp maxima and same for evenings.
The light people are getting influences their physiology.
115
What are the effects of morning and evening light on skin temp maxima?
Increased morning light significantly advances the time of skin temp maxima.
Increased evening light significantly delays the time of skin temp maxima.
116
Outline the Brooks et al (2023) study into diurnal rhythms of wrist temperature from the biobank.
**METHODS:**
- Measured wrist temperature over a week.
- Identified the chronotype using this information.
- Then asked several years later, based on the wrist temp rhythms, what are the chances of developing different diseases?
**RESULTS:**
- Those with a lower amplitude of a rhythm were more likely to develop a condition - they must have some issue in their rhythm.
- 10/20% risk differences based on low amplitude rhythms.
117
Outline the Didikoglu et al (2023) study into light exposure, sleep timing and sleepiness while awake in adults.
**METHODS:**
- Used light sensors tuned to the melanopsin activation curve instead of lux.
- Put these on participants for more than a week.
- Then using an app took qualitative judgements on how sleepy they were.
**RESULTS:**
- The relationship between the light they are experiencing and how aware they are showed that the brighter the light, the more alert they felt.
- The relationship between sleepiness and time of the day showed that getting light in the morning and middle part of the day leads to people rating themselves as being more alert.
Thus, evidence for light directly impacting arousal/alertness - one element of mood perhaps.
118
Outline the Burns et al (2023) study into day and night light exposure and how they are associated to psychiatric disorders.
METHODS:
- Took ~100,000 people and looked at the light exposure throughout the day, breaking it down into quartiles.
- Further investigated the 25% who got the most and least light per day.
- Did this for both night and day.
RESULTS:
- If you get more light later in the day, increases your risk of depression, combined with less light during the day.
- Bright days and dark nights decrease your chance of developing these mental health conditions.
119
Outline the findings from the Windred et al (2023) study into light in day and night and how it effects mortality.
They looked at the relationship between light exposure and the chance of dying of something.
Compared the relative risk/hazard ratio of having HIGH light exposure to the circadian time of light exposure.
If you have high exposure during the day time, you have a reduced risk of dying.
If you have high exposure during the night, you have an increased risk of dying.
Significant effects were shown too.
120
What did Windred et al (2023) show about the relationship between light during day and night and the mortality rate.
Dim days and bright nights increase the risk of dying by >50% in people over 40.
121
Outline the Kent et al (2022) into circadian lipid and hepatic protein entrainment.
METHODS:
- Looked at people being induced into different timing schedules between light, activity and food.
- Asked what happened in the core clock and hepatic proteins and lipids in the liver.
RESULTS:
- The amplitudes of the lipids/proteins are a lot higher.
- Also, the phases are different as when the melatonin delays the cholesterol advances etc.
**Shows good evidence for desynchrony across the body in response to shift-work esc stimuli.**
122
Briefly describe the Bowman et al (2021) into wearables.
METHODS:
- Used fitbits and HR trackers.
- Subtracted the HR associated with footsteps to give a trace of heart rates independent of activity.
- Used Medics students on shift work.
RESULTS:
- Showed that it takes a while for rhythms to realign with the new schedule.
- Heart rhythm seems to track the main clock as the entrainment matches the SCN.
