Immune Modulators Flashcards
What is the general purpose of B cells?
They produce antibodies
What is the general role of antigen presenting cells?
they prepare the antigen for recognition
What do stimulatory cytokines do? Give an example of one
They activate the immune system
IL1 and IL2, as well as TNF are exmaples
What is the purpose of Cell adhesion molecules?
they are immunoglobulin superfamiies which localize the response
ex) integrins
what is the role of inhibitory cytokines?
they inhibit the response
ex) IL4, IL10, and IL13
Describe the B cell immune defense
- invading microbe recognized as antigen
- antigen recognized by B cell which presents the antigen on its surface
- B cell receptor = antibody
- Bcell connects to helper T cell, which releases IL2
- Plasma cell releases prepared antibodies
- antibodies attack microbe and are thus marked for destruction
- memory cell is coated in now recognizable antibodies
Describe the T cell immune defense
- cell with virus presents part of the viral antigen on its head
- infected cell binds to helper T cell via T cell receptor that fits the particular antigen
- helper T cell releases IL2- which causes the proliferation of cytotoxic T cells specific to this antigen
- cytotoxic T cells bind to infected cells and destroy
What is lupus erythematosus?
–antibody to DNA histone complex ie anti-nuclear factor
What is rheumatoid arthritis?
autoimmune disease –due to formation of rheumatoid factor which is an antibody to IgG leading to complement activation
what is myasthenia gravis?
autoimmune disease –due to antibody formation to nicotinic acetylcholine receptors
what is Thyroiditis?
autoimmune disease
–due to antibodies to thyroid tissue
Graves disease due to increased thyroid hormone production due to antibodies to TSH receptor
What is multiple sclerosis?
- Presence of “scars” on brains
- Autoimmune disease
- Brain-reactive T-cells cause demyelination and destruction of neurons
- Evidence of a role for B-cells as well
- Leads to paralysis and death
What is Chrohn’s disease?
•Form of inflammatory bowel disease affecting all layers of the intestine
Associated with diarrhea, cramps, bloody stools and weight loss
what is psoriasis?
autoimmune skin disease
how to cytotoxic immunosuppressants work?
- They act by targeting dividing cells
- include alkylating agents, folic acid analogs and purine derivatives
- also used as anti-cancer agents
- can be very toxic
Describe how cyclophosphamide is used as an immune suppressant
it is an Alkylator
- include alkylating agents, folic acid analogs and purine derivatives
- also used as anti-cancer agents
- can be very toxic
Describe how methotrexate is used as an immunosuppressant
It is an antifolate
- act by interfering with dihydrofolate reductase necessary for DNA synthesis
- inhibits replication of B and T-cells
- used in rheumatoid arthritis and psoriasis and in combination with cyclosporine to prevent GvHD
- Dose used in RA is much lower than dose used for cancer
- Anti-inflammatory effect is not inhibited by folic acid supplementation
- Method of action is unclear but in RA
–MTX is poly-glutamated (long half-life)
–Inhibits Aminoimidazole carboxamidoribonucleotide (AICAR) transformylase
–Leads to increased adenosine production
Anti-inflammatory via adenosine receptors
describe methotrexate toxicity and how we combat this
- we give Folinic acid supplementation to prevent side effects
- Hepatotoxicity
- Pulmonary damage – pulmonary fibrosis/pneumonitis
- Myelosuppression/blood dyscrasias
- Gastrointestinal problems such as nausea, stomach upset, and loose stools
- Stomatitis or soreness of the mouth
- Infection
- Alopecia
What is Mitoaxantrone? What is it used for?
- Anti-cancer agent approved for MS
- Inhibits topoisomerase II
- Intercalates into DNA
- Serious toxicity esp cardiotoxicity
- Not a first choice treatment
What is Doxorubicin? What is it used for? how does it work?
- anthracycline antibiotics which intercalate with DNA
- doxorubicin inhibits B-cell function more than T-cell and does not inhibit macrophage or NK function
- daunorubicin inhibits macrophage function
- can cause cardiomyopathy
What is Azathioprine? How does it work?
it is a purine analog
- metabolised to mercaptopurine which inhibits DNA synthesis
- inhibits antibody production and cell-mediated immunity
- has no effect on NK cells but inhibits phagocytic cells
- causes monocytopenia
- used with prednisone to
prevent transplant rejection
What is Mycophenolate Mofetil?
- converted to active metabolite mycophenolic acid which inhibits inosine monophosphate dehydrogenase (IMPDH)
- IMPDH is essential for guanine nucleotide synthesis
- immunosuppressive and anti-proliferative
- more potent against IMPDH type II in lymphocytes
- used in renal transplants as prophylaxis with calcineurin inhibitors
What is Leflunomide?
- inhibits B- and T-cells
- mechanism of action is unknown but may involve inhibition of dihydroorotate dehydrogenase (DHODH)
- DHODH is essential for de novo pyrimidine synthesis
- Used for RA
- side effects are mild GI disturbance
- Active metabolite Teriflunomide also approved for MS
What is Cladribine?
- Adenosine analogue
- Inhibits adenosine deaminase
- Orally active
- Approved for treatment of hairy cell leukaemia
- Development for MS halted
–Lack of evidence of benefit
–Indication dropped by Merck
–Currently under consideration by EMA
Discuss Cladribine toxicity
•Myelosuppression
–Neutropenia
–Anemia
–Thrombocytopenia
- Fever
- Infections including sepsis
Describe the effects of glucocorticoids
- These inhibit phospholipase A2
- reduce the production of IL-1 and 2, interferon, prostaglandins and leukotrienes
- decreases basophils, eosinophils and monocytes but increase in neutrophils
- lymphocytes are also reduced (T>B; CD4+>CD8+)
- adverse effects on carbohydrate metabolism
Describe the use of NSAIDs
- inhibit cyclooxygenase production of prostaglandins
- prevent actions of IL-1 which acts through phospholipase A2
- have adverse effects on GIT
What is the role of IL2?
- IL-2 is a key mediator of immune function- acts on IL2 receptor
- Regulation of IL-2 function is a key strategy in pharmacotherapy
–Increase IL-2 levels
–Decrease IL-2 levels
–Block IL-2 receptors
–Block IL-2 signalling
- Recombinant IL2 is used in the treatment of cancer
What is cyclosporine?
- a cyclic undecapeptide - a fungal metabolite (Tolypocladium inflatum)
- found to inhibit mixed lymphocyte reaction (MLR) but was not cytotoxic (1972)
- inhibits antibody production against T-cell-dependent antigens (sheep erythrocytes) but not T-cell independent antigens (LPS)
*according to summary slide = complexes in the cell with immunophilins called cyclophilins. It inhibits the phosphatase activity oc calcineurin and hence prevents the nuclear translocation of NFAT and the transcription of severl lymphocye activation generated cytokines
What is Tacrolimus?
- macrolide antibiotic isolated from fungus (Streptomyces tsukubaensis)
- found to inhibit MLR (1980’s)
- structurally unrelated to cyclosporine
- similar activity to cyclosporine but more potent (10-100x)
How does Tacrolimus work?
•Tacrolimus & CsA inhibit gene transcription
–IL-2, 3&4
–GM-CSF
–TNFa
–IFNg
•specific for pathways involving increase in intracellular Ca2+ (e.g., T-cell receptor)
*according to summary slide - it complexes in the cell with immunophilins called FKBP12. Inhibits the phosphatase activity of calcineurin and hence prevents the nuclear translocation of NFAT and the expression of several lymphocyte activation-generated cytokines
What are immunophilins?
a family of intracellular receptors - that are isomerases involved in protein folding
Describe Rapamycin
- structural homolog of FK506- FK506 normally inhibits the formation of IL2
- existing antibiotic shown to have immunosuppressant activity (1989)
- isolated from Streptomyces hygroscopicus
- similar profile to FK506
- Binds to FKBP
*according to summary slide, Rapamycin - inhibitor of the cell kinase mTOR- complexes in the cell with the same immunophilins that complex tacrolimus FKBPs. It prevents the translation of mRNA encoding regulator of the cell cycle which result in the blockage of progression from the G1 to S phase
What are the targets of Rapamycin?
- rapamycin-FKBP complex does not inhibit calcineurin or gene induction
- rapamycin inhibits signal transduction by IL-2 receptor
- rapamycin-FKBP binds to targets of rapamycin (mTOR 1) a phosphatidylinositol 3-kinase
- Leads to reduced expression of adhesion molecules including sphingosine-1-phoosphate receptor
- Causes cell cycle arrest at G1
What is the clinical use for rapamycin?
Immuno suppresion
- used for prevention of allograft rejection and in autoimmune diseases
- Rapamycin can be used in conjunction with cyclosporine
- Increases levels of memory T-cells
- Increases longevity in mice by 10%
*used on coated stents to prevent rejection
Describe how Rapamycin is used in Cancer treatment
•mTOR implicated in cancer
–Renal cell carcinoma (RCC)
–Melanoma
–Breast cancer
•Everolimus & temsirolimus approved for RCC (2009)
–
Describe the toxicity risks of rapamycin
- less toxic than the cytotoxic immunosuppressants but nephrotoxicity is a problem
- cause of nephrotoxicity is probably due to endothelin release and inhibition of NOS
- FK506 appears to activate NFkB in fibroblasts leading to increased IL-6 production in kidney
- Rapamycin has less toxicity but causes dyslipidemia
What is Denileukin Diftitox?
- IL-2 and diphtheria toxin fusion protein
- Binds to cells expressing high affinity IL-2 receptor
- Inhibits protein synthesis resulting in cell death
- Used to treat certain leukemias
–Recurrent cutaneous T-cell lymphoma
Describe the ‘co-stimulatory’ Tcell activation
•T-cell receptor cannot trigger activation alone and requires co-stimulatory receptors
–CD28 activation is also required
–APC B7-1 (CD80) & B7-2 (CD86) are CD28 ligands
•Activated T-cells express CTLA-4
–Inhibits T-cell activation
–Ligands are B7-1 & B7-2
What is Abatacept?
- CTLA-4 fusion protein
- Binds to B7-1&2 preventing their interaction with CD28
- Reduces TNFa, IFNg and IL-2 secretion
- Approved for use in RA
What is Belatacept?
•Abatacept has higher affinity for B7-1 (CD80) than B7-2 (CD86)
–Effective in RA and not transplantation
•Belatacept differs from abatacept in two amino acids and has higher affinity for CD86
–Approved for organ transplantation (2011)
What is Ipilimumab?
monoclonal antibody that binds to CTLA4 and blocks the inhibitory pathway
approved for treatment of melanoma
What is Alefacept?
•Alefacept is a fusion protein- binds to CD2-
(CD2 (LFA-2) is another co-stimulatory receptor on T-cells It binds LFA-3 on antigen presenting cells)
–LFA-3
–Fc portion of IgG1
- Approved for use in plaque psoriasis
- Currently not available
How does Alefacept work?
- Binds to CD2 on memory T-cells preventing activation
- Triggers NK cell-mediated apoptosis of activated T-cells
What is the antiCD28 antibody?
- Superagonist antibody
- Activates immune system
- In animal models increases type 2 helper cells and regulatory T cells
- Showed benefit in animal autoimmune disease models
- In human study serious adverse effects
–Cytokine storm
–Systemic inflammatory response syndrome (SIRS)
How do we define SIRS? (systematic inflammatory response syndrome)
•Defined as 2 or more of
–Fever of > 38°C or < 36°C
–Heart rate > 90 beats per minute
–Respiratory rate of more than 20 breaths/min or PaCO2 < 32 mm Hg
Abnormal WBC (>12,000/mL or <4,000/mL or >10% bands)
What causes SIRS?
- May be due to infectious or non-infectious causes
- Due to activation of pro-inflammatory cytokines
–TNF
–IL-1,6&8
–IFNgamma
What is the role of adhesion molecules ?
- Immune cells must adhere to target to be effective
- Full activation often requires adhesion
- Adhesion is mediated by families of adhesion receptors
–Integrins
–Immunoglobin superfamily
What are integrins?
Family of cell adhesion molecules - all are alpha beta dimers
•Involved in many cellular functions
–GPIIb/IIIa (aIIbb3) on platelets
– b2 integrins on lymphocytes
•Ligands are usually proteins
What is Falizumab?
- Monoclonal antibody
- Blocks T-cell binding to endothelial cells
- Used in the treatment of psoriasis
- Withdrawn from the market due to PML
What is Natalizumab?
- Monoclonal antibody
- Binds to a4 integrins (a4b7 & a4b1)
- Thought to block binding of inflammatory cells to endothelium
- Prevents infiltration by lymphocytes into brain
How does Natalizumab work? What are its clinical uses?
blocks binding of inflammatory cells to endothelium
shows some benefit in MS
What is PML?
- Progressive multifocal leukoencephalopathy
- Due to re-activation of JC virus in the brain
- Herpes virus 6 re-activation also seen
- High mortality (50%)
Why do we target sphingosine 1 phosphate?
because the Sphingosine 1 phosphate receptor is an endothelial differentiation gene
S1P triggers lymphocyte egress from lymphoid tissue
What is Fingolimod?
it is a derivative of fungal isolate
- Orally active S1P1 receptor agonist, requires phosphorylation
- Causes receptor internalization
–Prevents egress of lymphocytes from lymphoid tissue in response to S1P
•Reduces lymphocyte levels
–Reduces hyperactivity of astrocytes
Fingolimod downregulates S1P1 preventing S1P mediated egress
Approved for MS
What are the adverse side effects of Fingolimod?
- Effects on heart rate and conduction
- Macular oedema
- 7 cases of skin cancers
- 1 definite case and 2 probable cases of PML
- Increased infections
–2 deaths from herpes virus infections
What is Siponimod?
next gen. S1P1 antagonist
•Selective for S1P1 & S1P5
What is Interferon Beta? (IFNB)
•IFNb-1a has been shown to provide benefit in MS- precise mechanism not known
IFNα and IFNβ contribute to immune dysfunction and tissue pathology, with IFNβ altering T-cell function and contributing to immune-mediated tissue injury
What are the three approaches to blocking TNF?
–Bind to receptor and block TNF binding
–Bind to TNF and block binding to receptor
–Block TNF synthesis
Give examples of TNF biologicals
•Etanercept
–Human TNFR2-Fcg fusion
•Infliximab
–Chimeric whole antibody
•Adalimumab & golimumab
–Whole human antibodies
•Certolizumab
–Humanized Fv conjugated with PEG
What is the risk in anti-TNF treated patients?
•Higher risk of infection in anti-TNF treated patients
–OR:2.0; 95% CI: 1.3-3.1
•TB is serious issue
–US population 6 per 100,000
–Infliximab patients 54 per 100,000
–Etanercept patients 28 per 100,000
•Pre-screening of patients is recommended
What is Glatiramer?
- Approved for use in the treatment of multiple sclerosis
- Inhibits auto-immune response
How does Glatiramer work?
- Induction of a specific Th2 population in periphery
- Reactivated in CNS due to cross-reactivity with myelin
- Secrete anti-inflammatory cytokines,
- Produce neurotrophic factors
- remyelination and axonal protection.
What is Dimethyl fumarate?
- Biogen-Idec
- Orally active
- Approved 2013 for treatment of MS
- MOA unclear
–Activation of Nrf2 (nuclear factor (erythroid-derived 2)-like 2)?
–Modulation of response to oxidative stress?
What is Imiquimod?
- Immune stimulator
- Used to treat genital warts and basal cell carcinoma
- Enhances cytokine production and increases infiltration of the tumour by immune cells
- Induces apoptosis
What is Intravenous IgG?
- Purified IgG from pooled plasma
- Can be used to treat patients with low levels of IgG
- Can be enriched for certain antibody types (e.g. anti-S. aureus antibodies)
- Blocks FcgRIIa receptor and thus has anti-inflammatory activity
- Approved for
–Immune thrombocytopenia
–Kawasaki syndrome
–Multifocal Motor Neuropathy
–Chronic Inflammatory Demyelinating Polyneuropathy
IL1 is targeted by what drugs for the treatment of what condition?
–Canakinumab (Multiple autoimmune disease including RA)
–Anakinra (RA)
IL-6 is targeted by what drug for treatment of what condition?
–Tocilizumab (RA)
CD20 is targeted by what drug for the treatment of what condition?
–Rituximab (RA, B-cell lymphoma)
CD3 is targetd by what drug for the treatment of what condition?
–OKT3 Muromonab (organ transplant)
CD52 is targetd by what drug for the treatment of what condition?
–Found on mature lymphocytes
–Alemtuzumab (MS, leukemia)
