Immune Modulation Flashcards
What are ways of boosting the immune system?
Vaccination
Replacement of missing components
Blocking immune checkpoints
Cytokine therapy
What are features of the adaptive immune response?
Wide repertoire of antigen receptors: Receptor repertoire is not entirely genetically encoded. Genes for segments of receptors are rearranged and nucleic acids deleted/added at the sites of rearrangement almost randomly. Potential to create in order of 1011 to 1012 receptors. Autoreactive cells are likely to be generated. Mechanisms must exist to delete or tolerise these autoreactive cells.
Exquisite specificity: Able to discriminate between very small differences in molecular structure.
What are antigen presenting cells?
APCs are cells that can present peptides to T lymphocytes to initiate an acquired immune response.
These cells include:
- Dendritic cell
- Macrophage
- B lymphocyte
What are types of osteoclasts?
Langerhans cells
Mesangial cells
Kupffer cells
Osteoclasts
Microglia
What is clonal expansion after exposure to an antigen?
T cells with appropriate specificity will proliferate and differentiate into effector cells (cytokine secreting, cytotoxic).
B cells with appropriate specificity will proliferate and differentiate to T cell independent (IgM) (memory and) plasma cells undergo germinal centre reaction and differentiate to T cell dependent IgG/A/E(M) memory and plasma cells.
Plasma cells secrete high affinity specific antibodies.
What is immunological memory?
Pre-formed pool of high affinity specific antibodies.
Residual pool of specific T and B cells with enhanced capacity to respond if re-infection occurs.
What are features of T-cell memory?
Longevity: Memory T cells are maintained for a long time without antigen by continual low-level proliferation in response to cytokines.
Different pattern of expression of cell surface proteins involved in chemotaxis/cell adhesion: These allow memory cells to access non-lymphoid tissues, the sites of microbial entry.
Rapid, robust response to subsequent antigen exposure: There are more memory cells. These cells are more easily activated than naïve cells.
What are features of B-cell memory?
Pre-formed antibody: Circulating high affinity IgG antibodies.
Longevity: Long lived memory B cells and plasma cells.
Rapid, robust response to subsequent antigen exposure: Memory B cells are more easily and rapidly activated than naïve cells.
How do vaccines promote immunity against influenza?
For influenza although CD8 T cells control the virus load it is antibody which provides a protective response.
Hemagglutinin (HA) is the receptor-binding and membrane fusion glycoprotein of influenza virus and the target for infectivity-neutralizing antibodies.
There is a clear correlation between resistance to infection and levels of IgG antibody to haemagglutinin (HA).
How is the BCG effective at mounting a protective response?
Attenuated, strain of bovine tuberculosis
Some protection against primary infection
Some protection against progression to active TB
T cell response is important in protection
What is the test for immunity against TB?
Mantoux test
Inject 0.1 ml of 5 tuberculin units of liquid tuberculin intradermally. The tuberculin used in the Mantoux skin test is also known as purified protein derivative, or PPD.
The patient’s arm is examined 48 to 72 hours after the tuberculin is injected.
The reaction is an area of induration (swelling that can be felt) around the site of the injection.
What are the different types of vaccines?
- Live vaccines
- Inactivated/Component vaccines
(Conjugates + Adjuvants increase immunogenicity) - RNA vaccines
- Adenoviral vector vaccines
- Dendritic cell vaccines
What are examples of live attenuated vaccines?
MMR
BCG
Yellow fever
Typhoid (oral)
Polio (Sabin oral)
Influenza (Fluenz tetra for children 2-17 years)
What are advantages of live attenuated vaccinations?
Establishes infection: Ideally mild symptoms.
Raises broad immune response to multiple antigens: More likely to protect against different strains.
Activates all phases of immune system. T cells, B cells: With local IgA, humoral IgG.
May confer lifelong immunity, sometimes just after one dose.
What are disadvantages of live attenuated vaccines?
Possible reversion to virulence (recombination, mutation): Vaccine associated paralytic poliomyelitis (VAPP, ca.1:750,000 recipients).
Spread to contacts: Spread to immunosuppressed/immunodeficient patients.
Storage problems.
What are examples of inactivated viruses?
Influenza (inactivated quadrivalent)
Cholera
Bubonic plague
Polio (Salk)
Hepatitis A
Pertussis
Rabies
What are examples of component/subunit vaccines?
Hepatitis B (HbS antigen)
HPV (capsid)
Influenza (recombinant quadrivalent - less commonly used)
What are examples of toxoid (inactivated toxin) vaccines?
Diphtheria
Tetanus
What are the advantages of inactivated/component vaccines?
No risk of reversion to virulent form
Can be used with immunodeficient patients
Storage easier
Lower cost
What are the disadvantages of inactivated/component vaccines?
Often do not follow normal route of infection.
Some components have poor immunogenicity.
May need multiple injections.
May require modification to enhance immunogenicity.
- Conjugate to protein carrier
- Adjuvant
What are conjugate vaccines made of?
Conjugate vaccines (often used in children)
Polysaccharide plus protein carrier.
Polysaccharide alone induces a T cell independent B cell response – transient.
Addition of protein carrier promotes T cell immunity which enhances the B cell/antibody response.
What are examples of conjugate vaccines?
Haemophilus Influenzae B
Meningococcus
Pneumococcus (Prevenar)
(Remember NHS for polysaccharide encapsulated bacteria)
What is an adjuvant to a vaccine?
Adjuvant increases the immune response without altering its specificity.
Mimic action of PAMPs (pathogen associated molecular patterns) on TLR (toll-like receptors) and other PRR (pattern recognition receptors).
What are examples of adjuvants?
Aluminium salts (humans)
Lipids: Monophosphoryl lipid A (humans HPV)
Oils: Freund’s adjuvant (animals)
What is an example of a mRNA vaccine?
SARS-CoV
How are mRNA vaccines made?
Infect E coli with plasmids containing DNA for spike protein.
Harvest plasmids from the cultures.
Excise DNA and transcribe to mRNA.
Complex with lipids to create the vaccine.
How do mRNA vaccines work?
Inject mRNA/lipid complexes:
- Non-infectious
- Non-integrating
- Degraded within days
mRNA enters cells (e.g. muscle cells, endothelial cells, fibroblasts, dendritic cells).
mRNA translated and spike protein synthesised/expressed on surface.
Stimulates immune response including B cells/antibodies and T cells.
What are adenoviral vector vaccines?
DNA of relevant protein (Covid spike protein) inserted to viral vector to produce vaccine.
AZ Covid vaccine vector: ChAdOx1-S
Sputnik Covid vaccine vector: Adenovirus types 26 and 5
Infect cells in vivo
Transcription/translation to produce protein
Stimulates immune response including B cells/antibodies and T cells.
What are dendritic cell vaccines?
Acquired defects in DC maturation and function associated with some malignancy suggests a rationale for using ex vivo–generated DC pulsed with tumour antigens as vaccines.
Focus on tumour associated antigens or mutational antigen.
What is Sipuleucel-T Provenge vaccine?
Personalised immunotherapy for prostatic cancer.
Remove white cells from patient’s blood (leukaphoresis).
APCs are harvested and incubated with recombinant protein PAP-GMCSF (Prostatic acid phosphatase-granulocyte macrophage colony stimulating factor).
APCs infused back to patient.
Stimulates patient’s immune response.
How can missing components of immune systems be replaced?
Haematopoietic stem cell transplantation - donor or autologous.
Antibody replacement
What are indications for stem cell transplant?
Life-threatening primary immunodeficiencies:
- Severe combined immunodeficiency
- Leukocyte adhesion defect
Haematological malignancy:
- Offers potential for complete and permanent cure
What is antibody replacement?
Human normal immunoglobulin prepared from pools of >1000 donors. Contains preformed IgG antibody to a wide range of unspecified organisms.
Blood product:
- Donors screened for Hep B, Hep C and HIV
- Further treated to kill any live virus
Administration
IV or SC
What are indications for antibody replacement therapy?
Primary antibody deficiency:
- X linked agammaglobulinaemia
- X linked hyper IgM syndrome
- Common variable immune deficiency
Secondary antibody deficiency:
- Haematological malignancies
- Chronic lymphocytic leukaemia
- Multiple myeloma
What is specific immunoglobulin modulation?
Human immunoglobulin used for post-exposure prophylaxis (passive immunisation).
Derived from plasma donors with high titres of IgG antibodies to specific pathogens.
Which diseases can be modulated using specific immunoglobulins?
Hepatitis B immunoglobulin: Needle stick/bite/sexual contact – from HepBSag+ve individual.
Rabies immunoglobulin: To bite site following potential rabies exposure.
Varicella Zoster immunoglobulin: Women <20 weeks pregnancy or immunosuppressed where aciclovir or valaciclovir is contraindicated.
Tetanus immunoglobulin: No specific preparation available in UK – use IVIG for suspected tetanus.
What are examples of adoptive cell transfer (T-cells)?
Virus specific T cells
Tumour infiltrating T cells (TIL – T cell therapy)
T cell receptor T cells (TCR - T cell therapy)
Chimeric antigen receptor T cells (CAR – T cell therapy)
What are indications for virus specific T-cell therapy?
EBV related B cell lymphoproliferative disease
Severe persistent viral infection in immunocompromised
What are indications for chimeric antigen receptor T-cell therapy?
Acute lymphoblastic leukaemia
Non-Hodgkin lymphoma
CAR T cells less successful in solid tumours
How does chimeric antigen receptor T cell therapy work?
T-cells with chimeric receptors targeting CD19:
- Patient’s own T cells
- Genetically engineered to express receptor
- Expanded in vitro
Used for acute lymphoblastic leukaemia in children.
Used for some forms of non-Hodgkin lymphoma.
What is ipilimumab and how does it function?
Action:
- Antibody binds to CTLA4
- Blocks immune checkpoint
- Allows T cell activation
Indications: Advanced melanoma
Complications: Autoimmunity
What are Pembrolizumab and Nivolumab and how do they function?
Action:
- Antibody binds to PD-1
- Blocks immune checkpoint
- Allows T cell activation
Indications and dosing:
- Advanced melanoma
- Metastatic renal cell cancer
Complications: Autoimmunity
What are the clinical uses of recombinant cytokines?
Aim: Modify immune response
Examples:
-
Interleukin 2 – Stimulate T cell response:
Renal cell cancer - Interferon alpha 2a – Immunomodulatory effect: Behcet’s
-
Interferon alpha – Antiviral effect:
- Hepatitis B
- Hepatitis C (with ribavirin)
- Interferon gamma – Enhance macrophage function: Chronic granulomatous disease.
The purpose of vaccination is to stimulate and enhance immunological memory. Which type of cells mediate immunological memory?
A. Neutrophils
B. B and T lymphocytes
C. Platelets
D. Eosinophils
E. Macrophages
B. B and T lymphocytes
Which of the following vaccines should NOT be given to an immunosuppressed individual?
A. BCG - bacilli Calmette-Guerin
B. Diphtheria toxoid
C. Quadrivalent inactivated influenza vaccine
D. Polio (Salk – injected)
E. Pfizer Covid mRNA vaccine
A. BCG - bacilli Calmette-Guerin
A 23 year old has metastatic melanoma. Which of the following may reduce disease progression?
A. BCG vaccination
B. Bone marrow transplantation
C. CAR-T cells with specificity for CD19
D. Nivolumab, an antibody specific for PD-1
E. Normal human immunoglobulin
D. Nivolumab, an antibody specific for PD-1
What are methods of suppressing the immune system?
- Steroids
- Anti-proliferative agents
- Plasmapheresis
- Inhibitors of cell signalling
- Agents directed at cell surface antigens
- Agents directed at cytokines and their receptors
What is the effect of corticosteroids on prostaglandins?
Phospholipase A2: Breaks down phospholipids to form arachidonic acid which is converted to eicosanoids (e.g. prostaglandins, leukotrienes) by cyclo-oxygenases.
Corticosteroids inhibit phospholipase A2: Blocks arachidonic acid and prostaglandin formation and so reduces inflammation.
What is the effect of corticosteroids on phagocytosis?
Decreased traffic of phagocytes to inflamed tissue.
Decreased expression of adhesion molecules on endothelium.
Blocks the signals that tell immune cells to move from bloodstream and into tissues. Results in transient increase in neutrophil counts.
Decreased phagocytosis.
Decreased release of proteolytic enzymes.
What is the effect of corticosteroids on lymphocyte function?
Lymphopenia
Sequestration of lymphocytes in lymphoid tissue: Affects CD4+ T cells > CD8+ T cells > B cells
Blocks cytokine gene expression.
Decreased antibody production.
Promotes apoptosis.
What are side effects of corticosteroids?
Metabolic effects: Diabetes, central obesity, moon face, lipid abnormalities, osteoporosis, hirsuitism, adrenal suppression.
Other effects: Cataracts, glaucoma, peptic ulceration, pancreatitis, avascular necrosis.
Immunosuppression: Infection.
What are anti-proliferative immunosuppressants?
Cytotoxic agents.
Drugs (selected):
- Cyclophosphamide
- Mycophenolate
- Azathioprine
Action:
- Inhibit DNA synthesis
- Cells with rapid turnover most sensitive
Toxicity:
- Bone marrow suppression
- Infection
- Malignancy
- Teratogenic
What are the side effects of cyclophosphamide?
Toxic to proliferating cells:
- Bone marrow depression
- Hair loss
- Sterility (male>>female)
Haemorrhagic cystitis:
- Toxic metabolite acrolein excreted via urine
Malignancy:
- Bladder cancer
- Haematological malignancies
- Non-melanoma skin cancer
Infection: Pneumocystis jiroveci
What are side effects of azathioprine?
Bone marrow suppression:
Cells with rapid turnover (leucocytes and platelets) are particularly sensitive. 1:300 individuals are extremely susceptible to bone marrow suppression.
- Thiopurine methyltransferase (TPMT) polymorphisms.
- Unable to metabolise azathioprine.
- Check TPMT activity or gene variants before treatment if possible; always check full blood count after starting therapy.
Hepatotoxicity: Idiosyncratic and uncommon.
Infection: Serious infection less common than with cyclophosphamide.
What are the side effects of mycophenolate mofetil?
Bone marrow suppression:
Cells with rapid turnover (leucocytes and platelets) are particularly sensitive.
Infection:
- Particular risk of herpes virus reactivation
- Progressive multifocal leukoencephalopathy (JC virus)
What is plasmapheresis and plasma exchange?
Aim: Removal of pathogenic antibody.
Patient’s blood passed through cell separator. Own cellular constituents reinfused. Plasma treated to remove immunoglobulins and then reinfused (or replaced with albumin in ‘plasma exchange’).
What are disadvantages of plasmapheresis?
Rebound antibody production limits efficacy, therefore usually given with anti-proliferative agent.
What are indications for plasmapheresis?
Severe antibody-mediated disease:
- Goodpasture syndrome: Anti-glomerular basement membrane antibodies.
- Severe acute myasthenia gravis: Anti-acetyl choline receptor antibodies.
- Antibody mediated transplant rejection/ABO incompatible: Antibodies directed at donor HLA/AB molecules.
What are calcineurin inhibitors?
Inhibit T cell proliferation/function.
Used in:
- Transplantation
- SLE
- Psoriatic arthritis
What are mTOR inhibitors?
Mechanistic Target of Rapamycin.
Inhibit T cell proliferation and function.
Used in: Transplantation.
What are Jak inhibitors (Jaknibs)?
Inhibit JAK-STAT signalling (associated with cytokine receptors). Influences gene transcription.
Inhibits production of inflammatory molecules. Effective in Rheumatoid arthritis, psoriatic arthritis, axial spondyloarthritis.
What is Apremilast?
PDE4 inhibitor
Inhibition of PDE4 leads to increase in cAMP.
Influences gene transcription via protein kinase A pathway.
Modulates cytokine production.
Effective in psoriasis and psoriatic arthritis.
What are agents directed at cell surface antigens?
Drugs:
- Rabbit anti-thymocyte globulin
- Basiliximab – anti-CD25
- Abatacept – CTLA4-Ig
- Rituximab – anti-CD20
- Vedolizumab – anti-a4b7 integrin
Actions include:
- Block signalling
- Cell depletion
- Inhibit migration
What is anti-thymocyte globulin?
Indications and dosing:
- Allograft rejection (renal, heart)
- Daily intravenous infusion
Action – multiple modes:
- Lymphocyte depletion
- Modulation of T cell activation
- Modulation of T cell migration
Toxicity:
- Infusion reactions
- Leukopenia
- Infection
- Malignancy
What is Basiliximab?
Antibody directed at CD25 (IL-2Ra chain).
Indications and dosing:
- Prophylaxis of allograft rejection.
- Intravenous given before and after transplant surgery.
Action: Blocks IL-2 induced signalling and inhibits T cell proliferation.
Toxicity:
- Infusion reactions
- Infection
- Concern re: long term risk malignancy.
What is Abatacept?
CTLA4–Ig fusion protein
Indications and dosing:
Rheumatoid arthritis: Intravenous 4 weekly; Subcutaneous weekly.
Action: Reduces costimulation of T cells via CD28.
Toxicity:
- Infusion reactions
- Infection (TB, HBV, HCV)
- Caution wrt malignancy
What is Rituximab?
anti-CD-20 antibody
Indications and dose:
- Lymphoma
- Rheumatoid arthritis
- SLE
- 2 doses intravenous every 6-12 months (RA)
Action: Depletes mature B cells.
Toxicity:
- Infusion reactions
- Infection (PML)
- Exacerbation CV disease
What is Vedolizumab?
Antibody specific for a4b7 integrin.
Indications and dosing:
- Inflammatory bowel disease.
- Intravenous every 8 weeks
Action: Inhibits leukocyte migration.
Toxicity:
- Infusion reactions
- Hepatotoxic
- Infection (? PML)
- Concern re malignancy
What is TNF-alpha?
TNFa is a pivotal cytokine in inflammation in many conditions.
TNFa blockade used in:
- Rheumatoid arthritis
- Psoriasis and psoriatic arthritis
- Inflammatory bowel disease
- Familial Mediterranean fever
What are anti-TNF-alpha antibodies?
Infliximab
Adalimumab
Certolizumab
Golimumab
When are anti-TNF-alpha antibodies used for?
Indications and dosing:
- Rheumatoid arthritis
- Ankylosing spondylitis
- Psoriasis and psoriatic arthritis
- Inflammatory bowel disease
- Subcutaneous or intravenous
Action: Inhibit TNFa
Toxicity:
- Infusion or injection site reactions
- Infection (TB, HBV, HCV)
- Lupus-like conditions
- Demyelination
- Malignancy
What is Etanercept?
TNF-alpha antagonist
Indications and dosing:
- Rheumatoid arthritis
- Ankylosing spondylitis
- Psoriasis and psoriatic arthritis
- Subcutaneous weekly
Action: Inhibits TNFa and TNFb.
Toxicity:
- Injection site reactions
- Infection (TB, HBV, HCV)
- Lupus-like conditions
- Demyelination
- Malignancy
What is IL-1?
IL-1 secretion driven via the inflammasome.
IL-1 blockade may be used in Familial Mediterranean Fever, Gout, Adult Onset Stills Disease.
What is IL-6?
IL-6 plays an important role in inflammation in rheumatoid arthritis.
IL-6 blockade using an anti-IL6 receptor antibody is effective in management of rheumatoid arthritis.
What are Tocilizumab and Sarilumab?
Antibodies directed at IL-6 receptor.
Indications and dosing:
- Castleman’s disease
- Rheumatoid arthritis
- Subcutaneous every 1-2 weeks
Action: Reduces macrophage, T cell, B cell, neutrophil activation.
Toxicity:
- Infusion reactions
- Infection
- Hepatotoxic
- Elevated lipids
- Caution wrt malignancy
What are IL-23 and IL-17?
IL23 – IL17 pathway important in spondyloarthritides and related conditions.
- Axial spondyloarthritis (AS)
- Psoriasis and psoriatic arthritis
- Inflammatory bowel disease (not anti-IL17 for IBD)
What is Guselkumab?
Ab vs p19 (alpha) subunit of IL23.
IL-23: IL-23 comprises p40+p19
Indications and dosing: Psoriasis, psoriatic arthritis; Subcutaneous every 8 weeks.
Action: Inhibits IL-23
Toxicity:
- Injection site reactions
- Infection (TB)
- Concern re malignancy
What are IL-4, IL-5 and IL13?
IL-4, IL-5 and IL-13 are key cytokines in Th2 and eosinophil responses.
IL-4/13 blockade using an antibody specific for the IL4 receptor alpha subunit may be used for eczema and asthma.
Anti-IL13 antibody may be used for management of eczema.
Anti-IL5 antibody is used for eosinophilic asthma.
What are RANK and RANK-ligand?
RANK ligand/RANK receptor pathway important in driving osteoclast differentiation and function.
Anti-RANK ligand antibody is used in management of osteoporosis.
What is Denosumab?
Antibody directed at RANK ligand.
Indications and dosing: Osteoporosis; Subcutaneous every 6 months.
Action: Inhibits RANK mediated osteoclast differentiation and function.
Toxicity:
- Injection site reactions
- Infection – mildly immunosuppressive
- Avascular necrosis of jaw
What are side-effects of biologic agents?
Infusion reactions:
- Urticaria, hypotension, tachycardia, wheeze – IgE mediated.
- Headaches, fevers, myalgias – not classical type I hypersensitivity.
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
What is the association between acute infection and immunosuppression?
- Risk often > 2 x background
- Avoid contact/wash hands etc
- Vaccination (avoid live vaccines)
- Temporarily stop immunosuppression in case of infection
- Consider atypical organisms
- Appropriate antibiotics
What is the association between chronic infections and immunosuppression?
Tuberculosis:
- History, Residence, Travel, Contacts, CXR, TB Elispot
- Prophylaxis or treatment if required
HBV and HCV:
- Check Hep B core antibody pre-treatment
- Check Hep C antibody pre-treatment
- Further investigate for active virus infection if serology is positive
HIV:
- Check HIV serology pre-treatment
- Balance benefits against possible risks
What is the association between JC Virus and immunosupression?
Common polyomavirus that can reactivate
Infects and destroys oligodendrocytes
Progressive multifocal leukoencephalopathy
Associated with use of multiple immunosuppressive agents
What is the association between immunosupression and malignancy?
- Lymphoma (EBV)
- Non melanoma skin cancers (Human papilloma virus)
- ?Melanoma
Risks appear lower with targeted forms of immunosuppression than with regimes used in transplantation.
What is the association between autoimmunity and immunosuppression?
- SLE and lupus-like syndromes
- Anti-phospholipid syndromes
- Vasculitis
- Interstitial lung disease
- Sarcoidosis
- Uveitis
- Autoimmune hepatitis
- Demyelination
A young woman with SLE is found to have osteoporosis. She has experienced weight gain and easy bruising and has a high blood glucose. Which drug is likely to have caused these effects?
A. Azathioprine
B. Anti-CD20 (rituximab)
C. Mycophenolate mofetil
D. Prednisolone
E. Anti-TNF alpha
D. Prednisolone
Rituximab is a monoclonal antibody specific for CD20 on B cells. It depletes B cells. For which one of the following diseases is it effective treatment?
A. Ankylosing spondylitis
B. Malignant melanoma
C. Multiple sclerosis
D. Osteoporosis
E. Rheumatoid arthritis
E. Rheumatoid arthritis
Which of the following are true about management of psoriasis and psoriatic arthritis?
A. It responds to inhibition of RANK ligand (denosumab).
B. It responds to CAR-T cells.
C. Treatment options include IL6 blockade or B cell depletion with rituximab.
D. Treatment options include inhibition of TNF alpha, IL23 or IL17A or use of a PD4 blocker or ciclosporin.
E. Treatment options include use of a checkpoint inhibitor such as nivolumab.
D. Treatment options include inhibition of TNF alpha, IL23 or IL17A or use of a PD4 blocker or ciclosporin.
