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 prednisolone
synthetic glucocorticoid
What is the difference between prednisolone and prednisone?
Prednisone is mainly used in the US - it is metabolised to prednisolone in the liver
How much endogenous steroid does the body produce per day?
Equivalent to 3-4 mg of prednisolone
Describe the effects of steroids on:
- Prostaglandins
- Phagocytes
- Lymphocyte Function
- Prostaglandins
- Inhibits phospholipase A2
- Phospholipase A2 is responsible for the conversion of phospholipids into arachidonic acid (which will then be converted to eicosanoids by COX)
- Inhibiting phospholipase A2 leads to a reduction in arachidonic acid and prostaglandin formation and, hence, a reduction in inflammation
- (same pathway as NSAIDS)
- Phagocytes - innate immunity
- Decrease traffic of phagocytes to inflamed tissue (reduces the expression of adhesion molecules on the endothelium)
- This leads to a transient increase in neutrophil count
- Decreased phagocytosis
- Decreases proteolytic enzymes
- Lymphocyte Function - adaptive imunity
- Lymphopaenia (sequestration in lymphoid tissue)
- Blocks cytokine gene expression
- Decreased antibody production
- Promotes apoptosis
effect of steroids on WBC
neutrophilia
leukoapenia
List some side-effects of corticosteroids.
- Central obesity
- Moon face
- Easy bruising
- Thin skin
- Osteoporosis
- Diabetes
- Cataracts
- Glaucoma
- Peptic ulceration
- Immunosuppression
List some examples of anti-proliferative agents.
- Cycophosphamide
- Mycophenolate
- Azathioprine
- Methotrexate
What is the mechanism of action of cyclophosphamide?
- Alkylates the guanine base of DNA which damages the DNA and prevents replication (affects B cells more than T cells)
Most toxic - antiproliferative
List some indications of cycolphosphamide.
- Multisystem connective tissue disease
- Vasculitis
- Anti-cancer
List some side-effects of cyclophosphamide.
- Toxic to proliferating cells - bone marrow suppression, sterility (mainly males), hair loss
- Haemorrhagic cystitis - due to toxic metabolic (acrolein) in the urine
- Malignancy - bladder cancer, haematological malignancy, non-melanoma skin cancer
- Teratogenic
- Infection (e.g. PCP)
Fertility consideration with cyclophosphamide
sperm and egg freezing
Abx prophylaxis with cyclophosphamide, or long-term steroids
Co-trimoxazole
Outline the mechanism of action of azathioprine.
- Metabolised by the liver to 6-mercaptopurine
- Blocks de novo purine synthesis (e.g. adenine and guanine)
- Prevents DNA replication
- Preferntially inhibits T cell activation and proliferation
Toxic to proliferating cells
List some indications for azathioprine.
- Transplantation
- Autoimmune
- Autoinflammatory (e.g. Crohn’s)
List some side-effects of azathioprine.
- Bone marrow suppression
- Hepatoxicity
- Infection
Which precaution must you take before starting a patient on azathioprine?
Check TPMT activity - 1 in 300 individuals have TPMT polymorphism which means that they are unable to metabolise azathioprine leading to bone marrow suppression.
Also check blood count after starting therapy
Outline the mechanism of action of mycophenolate mofetil.
- Blocking de novo nucleotide synthesis
- Prevents replication of DNA
- Affects T cell proliferation more than B cells
List some indications for mycophenolate mofetil.
- Transplantation
- Autoimmune disease
- Vasculitis
List some side-effects of mycophenolate mofetil.
- Bone marrow suppression
- Teratogenic
- Infection - particularly HSV reactivation and Progressive multifocal leukoencephalopthy caused by JC virus
Describe how plasmapheresis works.
- The patient’s blood is passed through a separator where the pathogenic immunoglobulins are removed and the plasma is reinfused
What is the main issue with plasmapheresis?
- Rebound antibody production - although antibodies have been removed, the plasma cells are still there
NOTE: therefore, anti-proliferative agents are often given alongside plasmapheresis