Imm - Immune modulation Flashcards
What are the immune modulatory methods of boosting the immune response
Vaccination
Replacement of missing components
Blocking immune checkpoints
Cytokine therapy
What is the immune pathophysiology behind the vaccine functioning
- APCs present peptides to T cells (Cd4/8)
- Clonal expansion of appropriate T cells
- CD4 → release cytokines to activate B cells/others (slightly less expansion)
- CD8 → kills infected cells - Effector T cells die by apoptosis OR suvive as memory cells
- B cells differentiate to:
- T cell independent (IgM) memory cells OR
- T cell dependent (IgG/A/E) plasma cells
Give examples of antigen presenting cells
Dendritic cells
Macrophages (Langerhans cells, mesangial cells, Kupffer cells, osteoclasts, microglia, etc.)
B-lymphocytes
What are the advantages of memory cells
Longevity - persisting without antigen (low level proliferation in response to cytokines)
Different cell surface proteins and access to non-lymphoid tissues
Rapid- robust response to subsequent antigen exposure
Pre-formed, high affinity IgG antibodies present (B cells)
What are the ideal features of a vaccine
- Generates immunological memory
- Practical - single injection, easy storage, inexpensive
- No adverse effects
What are the types of vaccine
Live attenuated vaccines
Inactivated/component vaccines (inc. conjugates and adjuvants to increase immunogenicity
DNA vaccines
Dendritic cell vaccines
What are live attenuated vaccines and give examples
The organism is modified to limit pathogenesis
MMR
BCG
Yellow fever
Typhoid
Polio (Sabin - oral)
Vaccinia
Influenza nasal spray
What are the advantages and disadvantages of live attenuated vaccines
Establishes infections (ideally mild symptoms) Raises broad immune response to multiple antigens/strains
Activates all phases of immune system (T cells, B cells – local IgA, humoral IgG, etc.)
Often confer life-long immunity after one dose
Storage problems
Possible reversion to virulence
Spread to contacts (i.e. spread to immunocompromised/immunosuppressed)
Risk of paralytic poliomyelitis (VAPP)
What are inactivated/component/toxoid vaccines and give examples
Inactivated vaccines = influenza, cholera, polio (Salk - IM), HAV, Pertussis, Rabies
Component/subunit vaccines = HbS antigen, HPV (capsid), influenza
Toxoids (inactivated toxins) = diphtheria, tetanus
What are the advantages and disadvantages of inactivated/component/toxoid vaccines
No mutation or reversion
Can be used in immunodeficient patients
Easier storage and lower cost
Often do not follow normal route of infection
May have poor immunogenicity
May need multiple injections
May require conjugates or adjuvants
What are conjugate vaccines and give examples
polysaccharide + protein carrier:
Polysaccharide → T cell-independent B cell response (transient)
Protein → T-cell dependent B cell response (long-term)
HiB, meningococcus, pneumococcus (NHS), tetanus
What are RNA/DNA vaccines and give examples
Plasmid (vector) containing a pathogenic gene of choice is inserted into a muscle cell → Plasmid does NOT replicate but the gene encodes protein that is presented at the cell surface of the host cell (looks like infected cell)
Mimics the normal action of a virally infected cell and it stimulates T cell responses
COVID:
- mRNA: SARS-CoV-2
- adenoviral vectors: AstraZeneca
What are the advantages and disadvantages of RNA/DNA vaccines
Mimics virus cell
May be used to develop a cancer vaccine
Plasmid may integrate into the host DNA → autoimmune disease
What are adjuvants and give examples
increases the immune response without altering its specificity
Mimic the action of PAMPs on TLR and other PRRs
OR slows the release of the antigen to ensure a steady stream → prolonged immune response
Aluminium salts (humans)
Lipids (monophosphoryl lipid A; humans)
Oils (Freund’s adjuvant; animals)
ISCOMS
CpG DNA
Describe aluminium salt adjuncts
(ALUM)
most common, the primary adjuvant used in humans
Slows the release of the antigen to ensure a steady stream → prolonged immune response
Antigens are adsorbed to alum → slowly releases antigen → prolonged antigenic stimulation
Activates Gr1+ cells → IL-4 → helps to prime naive B cells
Describe CpG adjuvants
Stimulatory adjuvant, mimics PAMPs on TLR/PRRs
Unmethylated DNA rich in CpG (cytosine, phosphate, guanine) → activates TLRs (9) on APCs → stimulates expression of costimulatory molecules
Describe Complete Freund’s adjuvants
Water-in-oil emulsion containing mycobacterial cell wall components.
Mainly for animals, painful in humans (not used clinically)
Describe ISCOMS (Immune Stimulating Complex) adjuvants
Experimental
Multimeric antigen with adjuvant built in.
Cell-mediated immune response and humoral response
With saponin results in strong serum antibody response.
What are dendritic cell vaccines and give an exmaple
Used against tumours where dendritic cell function may be compromised
Load the patient’s dendritic cells with a tumour antigen → re-introduce them to the patient → boost response against tumour antigens
Requires antigens specific to the tumour and distinct from normal cells
E.g. Sipuleucel-T (Provenge) – prostate ca.
Describe the immune response to influenza
Antibodies are responsible for protection, CD8 T cells control viral load
Haemagglutinin (HA) is a fusion glycoprotein on the membrane → allows for detection via. a haemagglutinin inhibition assay
Antibody protection begins 7 days after vaccine and protection can last for around 6 months
Describe haemagglutinin inhibition assays
Normal red cells → clump to form a red spot
Adding influenza → HA makes cells stick together → diffuse colouration across the well
Add serum of someone with lots of ABs against HA → inhibits HA from making cells stick → cells clump at the bottom
This can be done using lots of wells and different dilutions → Higher dilutions with an inhibitory effect → greater level of antibodies the patient has against HA
The higher the antibody level the lower the likelihood of infection
Describe the tuberculosis vaccine
BCG
Attenuated strain of bovine tuberculosis
Provides some protection against primary infection, mainly progression from latent → active
T cell response important
Lasts 10-15 years
Describe Mantoux testing
? previous exposure to TB:
- Inject a small amount of liquid tuberculin (purified protein derivative / PPD) intradermally
- Area of injection is examined 48-72 hours after tuberculin injection
- The reaction is an area of swelling around the injection site
- Positive reaction wheal:
- >5mm (high-risk – i.e. immunocompromised, living with someone with TB)
- >10mm (medium-risk – i.e. healthcare workers)
- >15mm (low-risk)
What vaccines are given in adulthood
50yrs onwards: flu annually
65 yrs: Pneumococcal (PPV)
70 yrs: Shingles
Pregnancy (any age): Flu during appropriate season, DTaP/IPV from 16/40
gestation, pertussis from 16-32
What are the methods of replacing missing compounds
Haematopoietic stem cell transplantation
Antibody replacement
Specific immunoglobulin
Adoptive cell transfer (ACT)
What are the indications for Haematopoietic stem cell transplantation
Offers potential for complete and permanent cure:
Life-threatening immunodeficiency (e.g. SCID, leucocyte adhesion defect)
Haematological malignancy
Describe antibody replacement and what are the indications
Ig can be replaced with human normal Ig, prepared from pools of >1000 donors
Contains pre-formed IgG
Primary antibody deficiency
- Bruton’s X-linked hypogammaglobulinemia
- X-linked hyper-IgM syndrome
- Common variable immunodeficiency
Secondary antibody deficiency
- Haematological malignancies (CLL, MM)
- After bone marrow transplantation
Describe specific immunoglobulin donation and give examples
AKA passive immunisation
Directly administering pre-formed antibodies/immunoglobulins
Lasts for 3 weeks
HNIG (Human Normal Ig) – Hep A and Measles
HBIG (Hep B) – Hep B (needle stick, sexual contact)
HRIG (Human Rabies) – Rabies (around bites)
VZIG (Varicella Zoster) – Varicella (pregnant <20 weeks or immunosuppressed)
Paviluzimab – monoclonal antibody for RSV
What are the types of adoptive T cells transfer
ViS-T: Virus specific T cell therapy
TIL-T: Tumour infiltrating T cells
CAR-T: Chimeric antigen receptor T cells
TCR
Describe ViS-T/Virus specific T cell therapy
Indication: prevents development form EBV (in immunosuppressed) → B cell lymphoproliferative
Allogenic (donor) or autologous (pt) cells harvested and stimulated with EBV/antigen
→ expansion of EBV-specific T effector cells → reinfusion into patient
Describe TIL-T/Tumour infiltrating T cells and what are the indications
- Tumour is removed form the patient
- T cells in the tumour is stimulated with cytokines (IL2)
- T cells develop a response against the tumour
- Select and expand tumour infiltrating lymphocytes and reinfuse
Head & neck SCC, melanoma, lung and gynae ca.
Describe TCR adoptive T cell transfer
T cells engineered to express receptors specific to tumour antigens
Describe CAR-T cell therapy and what are the indications
Similar to TCR, but chimeric receptors also targets CD19 → greater immune response to tumour
1. T cells taken form the patient
2. Vector used to insert gene fragments into the T cells
- TCR → gene specific to TCR → recognises MHC PRESENTED peptides
- CAR therapy → chimeric receptors (B and T) → also recognises cell surface CD markers (CD19) and tumour antigens (Non-MHC)
ALL and NHL
Describe cytokine therapy and give examples
Aims to boost immune response to cancer and some pathogens
IL-2: Increase T cell response and cloncal expansion → renal Ca
Interferon alpha: antiviral → hep B and C, Kaposi sarcoma, hairy cell leukaemia, CML, melanoma, Bechets
Interferon beta → relapsing remitting MS
Interferon gamma: increases macrophage function → chronic granulomatous disease
What are the indications for immune checkpoint blockade and what are examples
Indications: advanced melanoma, metastatic renal ca.
Ipilimumab: melanoma
Pembrolizumab and Nivolumab: advanced melanoma
What is the MOA for Ipilimumab
Blocks immune checkpoints
CTLA4 and CD28 both expressed by T cells and both recognise the same antigens on APCs (CD80 and CD86)
CD28 + APC CD80/CD86 → transmit a stimulatory signal
CTLA4 + APC CD80/CD86 → transmit an inhibitory signal
Ab specific to CTL-A4 → binds to CTLA4 → all interactions of CD80/86 occurs through CD28 → boosting of the T cell response
What is the MOA of Pembrolizumab and Nivolumab
Monoclonal antibody specific for PD-1 (programmed death receptor)
PD-1 is found on Treg cells → binds to PD-L1/2 on APCs/tumour cells → t cell inactivation and death
Blocking PD-1 → T cells remain active and kills tumour cells
What are the immune modulatory methods of suppressing the immune response
Steroids
Anti-proliferative agents
Plasmapheresis
Inhibitors of cell signalling
Agents directed at cell surface antigens
Agents directed at cytokines
Describe how steroids suppress the immune response
Prostaglandin reduction: inhibits phospholipase A2 (usually phospholipid →PA2→ arachidonic acid →COX→ prostaglandins + leukotrienes (pro-inflammatory)
Phagocytes: Reduced adhesion molecule expression and blocked chemokines → reduced chemotaxis to inflamed tissue, reduced phagocytosis and reduced release of proteolytic enzymes
Lymphocyte dysfunction: lymphopaenia due to sequestration (CD4>CD8>B), blocks cytokine gene expression, decreased Ab production, apoptosis
What are the side effects of corticosteroids
Metabolic (Cushing’s Syndrome): Central obesity, Moon face, Diabetes, lipid disorders, osteoporosis, hirsutism, adrenal suppression
Others: Cataracts, glaucoma, peptic ulceration, pancreatitis, avascular necrosis
Immunosuppression
Give examples of anti-proliferative agents and what is the MOA
Inhibits lymphocyte proliferation by inhibiting DNA synthesis → rapid turnover cells are most affected
Cyclophosphamide
Mycophenolate
Azathioprine
What is the MOA for cyclophosphamide and what is it used for
Alkylates guanine on DNA → damages DNA and prevents replication
B cells > T cells
Indications: connective tissue disease, vasculitis with organ involvement (GPA, SLE), cancer
What are the side effects of cyclophosphamide
Toxic to proliferating cells (bone marrow suppression, sterility (mainly in males), hair loss)
Haemorrhagic cystitis (toxic metabolite (acrolein) is excreted in the urine)
Malignancy (bladder cancer, haematological malignancies, non-melanoma skin cancer)
Teratogenic
Infection (e.g. Pneumocystis jirovecii / PCP pneumonia)
What is the MOA of azathioprine and what is it used for
Metabolised by the liver → 6-mercaptopurine (purine analogue) → blocks de novo purine synthesis (A and G) → prevents DNA replication
T cells > B cells
Used for transplantation, auto-immune disease and auto-inflammatory disease (IBD, Crohn’s)
What are the side effects of azathioprine use
Bone marrow suppression (1 in 300 particularly vulnerable; check TPMT activity):
- Thiopurine methyl transferase (TPMT) polymorphisms → Unable to metabolise azathioprine (CHECK TPMT ACTIVITY or gene variants before treatment is started)
Hepatotoxicity
Infection (less common than with cyclophosphamide)
What is the MOA of mycophenolate mofetil and what is it used for
Blocks de novo guanosine nucleotide synthesis → prevents DNA replication
T cell > B cell
Transplantation, auto-immune disease, vasculitis
What are the side effects of mycophenolate mofetil
Bone marrow suppression (rapid turnover cells particularly vulnerable)
Teratogenic
Infection (herpes virus reactivation, progressive multifocal leukoencephalopathy / JC virus)
Describe plasmapharesis and what are the indications and the issues with this method
Removal of pathogenic antibodies from the plasma
Pt blood passed through a separator → Abs removes → cells and plasma reinfused
Goodpasture’s syndrome (anti-GBM)
Severe acute myasthenia gravis (anti-ACh-R)
Severe transplant rejection (antibodies against donor HLA)
Problem: rebound Ab production (plasma cells still present) → can give anti-proliferative agents at the same time to combat
Give examples of inhibitors of cell signalling
Calcineurin (ciclosporin, tacrolimus)
mTOR inhibitors e.g. sirolimus
JAK (tofacitinib)
PDE4 (apremilast)
Describe calcineurin inhibitors
Inhibits calcineurin → prevents T cell signalling → blocks IL2 production → reduced activation of T cells AFTER APC interaction → reduced clonal expansion and proliferation
What are the side effects of calcineurin inhibitors
Nephrotoxicity (ciclosporin = tacrolimus)
HTN (ciclosporin = tacrolimus)
Neurotoxic (ciclosporin = tacrolimus)
Diabetogenic (ciclosporin < tacrolimus)
Dysmorphic features (ciclosporin): Hirsutism, Gingival hypertrophy
Describe mTOR inhibitors and what is it used for
Inhibit T cell proliferation and function
Used in transplantation
Describe JAK inhibitors and what are they used for
Tofacitinib (JAK 1 and 3) or ruxolotinib (JAK 2)
Interferes with JAK-STAT signalling (important in transducing the signals from cytokine binding)
Influences gene transcription
Inhibits the production of inflammatory molecules
Indication = rheumatoid or psoriatic arthritis
Describe PDE4 (Phosphodiesterase 4) inhibitors and what are they used for
Apremilast
Increases cAMP → activates protein kinase A (PKA) → prevents activation of transcription factors → reduced cytokine production
Indication = psoriasis or psoriatic arthritis
Agents directed against cell surface antigens: What are the following drugs directed against and give one use:
Basiliximab
Abatacept
Rituximab
Vedolizumab
Natalizumab
Tocilizumab
Muromonab-CD3
Daclizumab
Efalizumab
Alemtuzumab (campath)
Basiliximab: anti-CD25 (no T prolif) - prophylaxis for allograft rejection
Abatacept: CTLA4 Ig (binds APCs → reduced T cell activation) → RhA
Rituximab: Anti-CD20 (depletes mature Bcellls) → Lymphoma, RhA
Vedolizumab: Anti-alpha-4-beta-7 integrin (cell migration) → IBD
Natalizumab (anti-alpha-4-beta-1 integrin (leukocyte arrest, cell migration) → MS, Crohn’s
Tocilizumab: anti-IL-6 (reduced macrophage) → Castleman’s, RhA
Muromonab-CD3: blocks CD3 on T cells → active allograft rejection
Daclizumab: IL-2 receptor Ab for CD25 → prophylaxis for organ transplant rejection
Efalizumab: anti-CDIIa (no T cell migration)
Alemtuzumab (campath): MA for CD52 (lymphocyte depletion): CLL< MS
Agents directed at cytokines: what are the following agents directed at and give an indication for each:
Infliximab
Adalimumab
Cerolizumab
Golimumab
Etanercept
Ustekinumab
Guselkumab
Secukinumab
Denosumab
Tocilizumab
Sarilumab
IL-1 blockade
IL-4/5/13 blockade
Infliximab: anti-TNFalpha → RhA, ankspond, psoriasis
Adalimumab: anti-TNFalpha (“)
Cerolizumab: anti-TNFalpha (“)
Golimumab: anti-TNFalpha(“)
Etanercept: anti-TNFalpha/beta (“)
Ustekinumab: anti-IL12 and IL-23 (psoriasis, PsorA)
Guselkumab: anti-IL-23: (“)
Secukinumab: Anti IL-17A (“)
Denosumab: anti-RANK ligand (osteoporosis, MM)
Tocilizumab: Anti-IL6 (RhA, Castleman’s)
Sarilumab: Anti-IL6 (RhA, Castleman’s)
IL-1 blockade (Familial Mediterranean, gout)
IL-4/5/13 blockade (eczema, asthma)
What are the side effects of biologics
Infusion reactions:
- Urticaria, hypotension, tachycardia, wheeze – IgE mediated
- Headaches, fevers, myalgias – not classical type I hypersensitivity
- Cytokine storm
Injection site reactions:
- Peak reaction at ~48 hours
- May also occur at previous injection sites (recall reactions)
- Mixed cellular infiltrates, often with CD8 T cells
- Not generally IgE or immune complexes
Acute infection (often 2x)
Chronic infection (TB, HBV, HCV, HIV, JC virus)
Malignancy:
- Lymphoma (EBV)
- Non-melanoma skin cancers (HPV)
- Melanoma (more in those treated with TNFa inhibitors)
Autoimmunity (i.e. SLE, anti-phospholipid syndrome, vasculitis, ILD, sarcoid, uveitis, AI hepatitis, demyelination)
