Immuno: Immune modulating therapies 2 Flashcards
List some approaches to suppressing the immune system.
- Steroids
- Anti-proliferative agents
- Plasmapheresis
- Inhibitors of cell signalling
- Agents directed against cell surface antigens
- Agents directed at cytokines
What is daily endogenous steroid secretion equivalent to in prednisolone?
Equivalent to 3-4 mg prednisolone
What is the effect of steroids on prostaglandins?
Corticosteroids inhibit phospholipase A2
- Phospholipase A2 converts phospholipids into arachidonic acid which is subsequently converted into prostaglandins and leukotrienes by cyclo-oxygenases
What is the effect of steroids on macrophages?
- Decreases macrocyte trafficking to site of inflammation
- Decreased endothelial adhesion molecule expression (results in transient neutrophilia)
- Decreases phagocytosis
- Decreases release of proteolytic enzymes
What is the effect of steroids on lymphocytes?
- Lymphopenia
- Blocks cytokine gene expression
- Decreases antibody production
- Promotes apoptosis
List some adverse-effects of corticosteroids.
- Metabolic: diabetes, central obesity, moon face, lipid abnormalities, osteoporosis, hirsuitism, adrenal suppression
- Other: cataracts, glaucoma, peptic ulceration, pancreatitis, avascular necrosis
- Immunosuppression: infection
List some examples of anti-proliferative agents.
- Cyclophosphamide
- Mycophenolate
- Azathioprine
- Methotrexate
What is the mechanism of action of cyclophosphamide?
Alkylates the guanine base of DNA which inhibits replication
Affects B cells more than T cells
List some indications of cyclophosphamide.
- Multisystem connective tissue disease (e.g. lupus)
- Vasculitis
- Anti-cancer (NHL)
List some adverse-effects of cyclophosphamide.
- Toxic to proliferating cells - bone marrow suppression, sterility (mainly males), hair loss
- Haemorrhagic cystitis - due to toxic metabolite (acrolein) in the urine
- Malignancy - bladder cancer, haematological malignancy, non-melanoma skin cancer
- Infection (e.g. PCP)
Most toxic antiproliferative
Outline the mechanism of action of azathioprine.
- Metabolised by the liver to 6-mercaptopurine
- Blocks de novo purine synthesis by inhibiting HGPRT
Hypoxanthine-guanine phosphoribosyltransferase
Preferentially inhibits T cell activation and proliferation
List some indications for azathioprine.
- Transplantation
- Autoimmune disease (e.g. RA)
- Autoinflammatory disease (e.g. Crohn’s)
List some adverse-effects of azathioprine.
- Bone marrow suppression
- Hepatoxicity (indiosyncratic and uncommon)
- Infection (less so than cyclophosphamide)
Which precaution must you take before starting a patient on azathioprine?
Check TPMT activity
- TPMT required for azathioprine inactivation and metabolism
- 1 in 300 individuals have TPMT polymorphism which means that they are unable to metabolise azathioprine leading to severe bone marrow suppression
TPMT - thiopurine methyltransferase
What drug interacts dangerously with azathioprine?
Allopurinol - inhibits xanthine oxidase
Outline the mechanism of action of mycophenolate mofetil.
Blocking de novo purine nucleotide synthesis by inhibiting IMPDH thus preventing DNA replication (thus inhibiting proliferation of T and B lymphocytes)
Inosine-5′-monophosphate dehydrogenase
Affects T cell proliferation more than B cells
List the indication for mycophenolate mofetil.
Transplant immunosuppression
List some adverse-effects of mycophenolate mofetil.
Bone marrow suppression
Infection
- Herpes virus reactivation
- Progressive multifocal leukoencephalopathy (JC virus)
Describe how plasmapheresis works.
The patient’s blood is passed through a cell separator where the autoreactive immunoglobulins are removed and cells and plasma are reinfused
What is the main issue with plasmapheresis?
Rebound antibody production - although antibodies have been removed, the plasma cells are still there
Therefore, anti-proliferative agents are often given alongside plasmapheresis
List some indications for plasmapheresis.
Severe antibody-mediated disease
- Goodpasture’s disease
- Severe acute myasthenia gravis
- Antibody-mediated tranplant rejection
Describe the mechanism of action of calcineurin inhibitors.
- Normally, TCR engagement leads to increased cytoplasmic calcium which binds to calmodulin leading to the activation of calcineurin
- Calcineurin then activates NFATc resulting in the upregulation of IL-2
- IL-2 acts back on T cells to stimulate activation and proliferation
Calcineurin inhibitors block this pathway, thereby blocking IL -2 production
Give two examples of calcineurin inhibitors.
- Ciclosporin
- Tacrolimus
List some indications for calcineuin inhibitors
- Transplantation
- Rheumatoid arthritis
- Severe atopic eczema
- Psoriasis and psoriatic arthritis
- IBD (UC)
What are the adverse-effects of calcineurin inhibitors?
- Increased risk of infection
- Hypertension
- Nephrotoxicty
- (also diabetes, neurotoxic and dysmporphic facies)
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What is the function of mTOR inhibitors and give an example?
Sirolimus - inhibits T cell activation and proliferation
Give an example of a JAK inhibitor.
Describe the mechanism of action of JAK inhibitors.
Tofacitinib (JAK1 and JAK3 inhibitor)
- Inhibits JAK-STAT signalling (associated with cytokine receptors)
- Influences gene expression thus inhibiting the production of inflammatory molecules
What are some indications for JAK inhibitors?
- Rheumatoid arthritis
- Ulcerative colitis
- Psoriatic arthritis
- Axial spondyloarthritis
Give an example of a PDE4 inhibitor.
Apremilast
What are some indications for PDE4 inhibitors?
- Psoriasis
- Psoriatic arthritis
For each of the following monoclonal antibodies, their basic mechanism of action
- Basiliximab
- Abatacept
- Rituximab
- Vedolizumab
- Natalizumab
- Basiliximab = anti-CD25 (alpha chain of IL-2 receptor)
- Abatacept = CLTA4-Ig
- Rituximab = anti-CD20
- Vedolizumab = anti-alpha4beta7 integrin
- Natalizumab = anti-alpha4beta1 integrin
What does the suffix (-cept) mean?
It is made up of a receptor fused to immunoglobulin
Describe how anti-thymocyte globulin is made. What is it used for?
- Human thymocytes (T cells and their precursors) are injected into a rabbit which produces a variety of antibodies against thymocytes
- This is then injected into patients and leads to T cell depletion
- It is effective in allograft transplant rejection
List some adverse-effects of anti-thymocyte globulin.
- Infusion reactions
- Leukopaenia
- Infection
- Malignancy
Describe the mechanism of action of basiliximab/daclizumab. What is the indication for its use?
- Targets CD25 (alpha chain of IL-2 receptor)
- Blocks IL-2R thus inhibiting T cell activation and proliferation
- Used as a prophylaxis against transplant rejection
What are some adverse effects of basilximab/daclizumab?
- Infusion reaction
- Infection
- Increases long term malignancy risk
Describe the mechanism of action of abatacept. What condition is it used for?
Used in rheumatoid arthritis
- APCs bind to T cell CTLA4 (inhibitory) and CD28 (stimulatory) via CD80 and CD86 receptors
- Abatacept binds to CD80 and CD86 and prevents CD28 engagement thus inhibiting co-stimulation required for T cell activation
Describe the mechanism of action of rituximab.
- Targets CD20 which is found on mature B cells
- This results in depletion of mature B cells
- No effect on plasma cells
List some indications for rituximab.
- B cell Lymphoma
- Rheumatoid arthritis
- SLE
NOTE: it is given as two IV doses every 6-12 months
What are some adverse-effects of rituximab?
- Infusion reaction
- Infection (PML)
- Exacerbation of CVD
Describe the mechanism of action of vedolizumab.
- Antibody that blocks alpha4beta7 integrin
- Inhibits leukocyte migration to site of inflammation
What is vedolizumab used for?
Inflammatory bowel disease
What are some adverse-effects of vedolizumab?
- Infusion reaction
- Hepatotoxic
- Infection (PML)
- Risk of malignancy
Describe the mechanism of action of tocilizumab.
- Antibody against IL-6 receptor
- Results in reduced activation of macrophages, neutrophils, T cells, and B cells
What are the main indications of tocilizumab?
- Castleman’s disease (IL-6-producing tumour)
- Rheumatoid arthritis
- Giant cell arteritis
List three types of anti-TNFα antibodies.
- Infliximab
- Adalimumab
- Certolizumab
- Golimumab
Given SC
Infliximab can also be IV
What is TNF-alpha?
It is a critical molecule in the cytokine cascade responsible for the inflammatory response in inflammatory conditions
List some uses of anti-TNFα antibodies.
- IBD (UC and Crohns)
- Ankylosing spondylitis
- Rheumatoid arthritis
- Psoriasis and psoriatic arthritis
- Familian Mediterranean fever
List some side-effects of anti-TNFα antibodies.
- Infusion reactions
- Infection (TB reactivation, HBV, HCV)
- Lupus-like conditions
- Demyelination
- Malignancy
Screen for latent TB before starting
Describe the mechanism of action of etanercept. What are some indications for its use?
- It is a decoy receptor that mops up TNFα thereby inhibiting its action
- Used in psoriasis and psoriatic and rheumatoid arthritis, and ankylosing spondylitis
NOTE: it is given as a SC injection
Describe the inflammasome pathway
What conditions is the IL-23 and IL-17 pathway important for?
Ankylosing spondylitis, psoriasis and psoriatic arthritis, IBD (not IL-17)
Which antibodies inhibit IL-17 and IL-23?
Secukinumab - IL-17
Guselkumab - IL-23
Which interleukins integral to the pathophysiology of asthma and eczema?
IL-4, IL-5, IL-13 are key cytokines in Th2 and eosinophil responses
Which antibodies can be used in the treatment of asthma and eczema?
Dupilumab - IL-4
Mepolizumab - IL-5
Tralokinumab - IL-13
Describe the mechanism of action of denosumab.
- RANKL is produced by osteoblasts and it acts on RANK receptors on osteoclasts
- It promotes osteoclast differentiation and function, thereby leading to increased bone resorption
- Osteoprotegrin is a natural decoy receptor for RANKL which regulates the system
- Denosumab binds to RANKL and reduces osteoclast differentiation and function
It is used for osteoporosis
What adverse reactions are common across immunosuppressive agents?
- Infusion and injection site reactions (biologics)
- Increased risk of acute infection
- Increased risk of chronic infection reactivation
- Increased of malignancy
- Increased risk of auto-immunity
List some types of infusion reaction.
IgE mediated (T1 hypersensitivity)
- Urticaria
- Hypotension
- Tachycardia
- Wheeze
Non-T1 hypersensitivity
- Headache
- Fever
- Myalgia
Describe injection site reactions
- Peak at 48 hours
- Reslts in cutaneous necrosis
- May also occur at previous injection sites (recall reactions)
- Mixed cellular infiltrate (CD8 cells)
- Not generally IgE or immune complexes
Describe the infection risk possed by immunosuppressive therapy and its management
- Risk of infection often >2x background risk
- Prevent with hygiene precautions and vaccination (avoid live vaccines)
- Temporarily stop immunosuppression in case of infection
- Consider atypical organisms and use appropriate antibiotics
Which diseases should you screen for before starting immunosuppression
- TB - Quantiferon
- HBV, HCV - serology
- HIV - serology
What is JC virus and why is it dangerous in immunosuppression?
- John Cunningham Virus
- Common polyomavirus - majority of population has been exposed to it
- Usually kept well under control by immune system
- In the case of severe immunosuppression, the virus can reactivate and destory oligodendrocytes, leading to PML
What malignancies are associated with immunosuppression?
- Lymphoma (EBV)
- Non-melanoma skin cancer (HPV)
- Melanoma
Risks appear lower with targeted forms of immunosuppression than with regimes used in transplantation