10. Immune modulating therapies II Flashcards
What are six approaches to suppressing the immune system?
- Steroids; 2. Anti-proliferative disease; 3. plasmapheresis; 4. inhibitors of cell signalling 5. agents directed against cell surface antigens 6. agents directed at cytokines
What are corticosteroids?
Synthetic glucocorticoids based upon naturally occurring steroids
What mineralocorticoid activity do steroids have?
They have NO mineralocorticoid activity
What corticosteroid is used in the UK and USA?
UK: prednisolone. USA: prednisone (metabolised into prednisolone in the liver)
What is the endogenous production of steroids?
Roughly equivalent to 5-7.5 mg
What are the effects of corticosteroids on prostaglandins?
Corticosteroids inhibit phospholipase A2. Phospholipase A2 is usually involved in the conversion of phospholipids into arachidonic acid which is then converted to eicosanoids (e.g. prostaglandins and leukotrienes) by COX. By inhibiting phospholipase A2, corticosteroids will block arachidonic acid and prostaglandin formation thereby reducing inflammation.
What is the effect of corticosteroids on phagocytes?
Decrease traffic of phagocytes to inflamed tissue by: reducing the expression of adhesion molecules on the endothelium; they also block the signals that tell immune cells to move from the bloodstream into tissues; this leads to a transient increase in neutrophil count. Decreased phagocytosis. Decreased release of proteolytic enzymes.
What is the effects of corticosteroids on lymphocyte function?
Lymphopaenia: sequestration of lymphocytes in lymphoid tissue; affects CD4 > CD8 > B cells. Blocks cytokine gene expression. Decreased antibody production. Promotes apoptosis.
What do corticosteroids affect, leading to decreased inflammation?
Effects on prostaglandins, lymphocyte function, and phagocytes
What are the side effects of corticosteroids?
Metabolic: central obesity; moon face; diabetes; lipid disorders; osteoporosis; hirstuitism; adrenal suppression. Others: cataracts, glaucoma, peptic ulceration, pancreatitis. Immunosuppression
What are anti-proliferative agents?
These are agents that inhibit lymphocyte proliferation
What are examples of anti-proliferative agents?
Cyclophosphamide, mycophenolate, azathioprine, methotrexate
What is the action of anti-proliferative agents?
Inhibit DNA synthesis, cells with rapid turnover are most sensitive
What is the mechanism of action of cyclophosphamide?
Alkylates guanine base of DNA. Damages DNA and prevents cell replication.
Affects B cells > T cells (tends to be used in antibody-mediated disorders). At high dose, affects all cells with high turnover
What are major indications for cyclophosphamide?
Multisystem connective tissue disease; vasculitis with severe end-organ involvement (e.g. GPA, SLE); anti-cancer agent
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. Pneumocystic jirovecii).
What is the mechanism of azathioprine?
Metabolised by the liver to 6-mercaptopurine. Blocks de novo purine synthesis (e.g. adenine and guanine). Prevents replication of DNA. Preferentially inhibits T cell activation and proliferation.
What are the indications for azathioprine?
Transplantation, auto-immune disease, auto-inflammatory disease (e.g. Crohn’s, UC)
What are the side effects of azathioprine?
Bone marrow suppression: cells with rapid turnover (e.g. leucocytes and platelets) are particularly susceptible. Hepatotoxicity. Infection.
What should be checked before giving azathioprine?
Bone marrow suppression is a side effect of azathioprine. Cells with rapid turnover are particularly susceptible. 1 in 300 individuals are extremely susceptible to bone marrow suppression. CHECK TPMT ACTIVITY or gene variants before treatment is started?
Why are 1 in 300 individuals are extremely susceptible to bone marrow suppression when administered azathioprine?
Thiopurine methyl transferase (TPMT) polymorphisms - unable to metabolise azathioprine
What are the mechanisms of mycophenolate mofetil?
Blocks de novo nucleotide synthesis; prevents replication of DNA; prevent T cell > B cell proliferation.
What are indications for mycophenolate mofetil?
Widely used in transplantation (alternative to azathioprine). Also used in autoimmune disease and vasculitis as an alternative to cyclophosphamide.
What are side effects of mycophenolate mofetil?
Bone marrow suppression (cells with rapid turnover are particularly sensitive); teratogenic; infection (particularly herpes virus reactivation and progressive multifocal leukoencephalopathy (JC virus))
What is the aim of plasmapheresis?
Remove pathogenic antibody
What happens in plasmapheresis?
The patient’s blood is passed through a separator. Own cellular constituents are reinfused. Plasma is treated to remove immunoglobulins and is then reinfused (or replaced with albumin in plasma exchange)
What are the issues of plasmapheresis?
Rebound antibody production (because although you’ve got rid of the antibodies, the plasma cells are still there) limits efficacy. Therefore, it is usually given with an anti-proliferative agent.
What are indications for plasmapheresis?
Severe antibody-mediated disease: Goodpastures syndrome, severe acute myasthenia gravis, severe transplant rejection (antibodies against donor HHLA)
How do calcineurin inhibitors work and what do they do?
Inhibitors of calcineurin will prevent T cell signalling. Therefore, it blocks IL2 production. IL2 normally acts on T cells and drives proliferation. So, calcineurin inhibitors will prevent T cell activation and proliferation.
What are examples of calcineurin inhibitors?
Ciclosporin and tacrolimus
What are the side effects of ciclosporin?
Nephrotoxicity (++), hypertension (++), neurotoxic (++), diabetogenic (+), dysmorphic features (+++)
What are the side effects of tacrolimus?
Nephrotoxicity (++), hypertension (++), neurotoxic (++), diabetogenic (++), dysmorphic features (-)
What should be monitored when calcineurin inhibitors are given?
Monitor BP and renal function
What is an example of a JAK inhibitor?
Tofacitinib (JAK1 and JAK3 inhibitor)
What do JAK inhibitors do?
Interferes with JAK-STAT signalling (important in transducing the signals from cytokine binding); influences gene transcription; inhibits the production of inflammatory molecules
What are JAK inhibitors effective in?
Rheumatoid arthritis
What is an example to PDE4 inhibitors?
Apremilast
How to PDE4 inhibitors work?
Phosphdiesterase 4 (PDE4) is important in the metabolism of cAMP (degrades cAMP into 5’-AMP). Blocking PDE4 leads to increase in cAMP. cAMP activates PKA which prevent activation of transcription factors. This leads to a decrease in cytokine production.
What are PDE4 inhibitors effective in?
Effective in psoriasis and psoriatic arthritis
Which inhibitors do these side effects correspond to? A. osteoporosis B. infertility C. progressive multifocal leukoencephalopathy D. neutropenia particularly if TPMT low E. nephrotoxicity
A. prednisolone B. cyclophosphamide C. mycophenolate mofetil D. azathioprine E. tacrolimus
What does ‘-cept’ mean?
‘-cept’ means that it is a receptor that is usually put on the end of IgG Fc component
How are rabbit anti-thymocyte globulins used?
Thymocyte (lymphocytes from the thymus gland) from humans were injected into rabbits. The rabbits then produced antibodies against the thymocytes of varying specificities (e.g. antibodies to CD2, CD3, CD4, CD8 etc.). The serum was then taken and injected into patients. This is very effective at targeting T cells, however it is very non-specific.
What is the main aim of anti-thymocyte globulin?
The main aim is to cause T cell depletion (thereby reducing the activation and migration of T cells)
What is rabbit anti-thymocyte globulin useful in?
Useful in allograft rejection
What are the side effects of anti-thymocyte globulins?
Infusion reactions; leukopaenia; infection; malignancy
What is basiliximab?
Antibody directed at CD25 (IL-2Ralpha chain)