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))