Interleukins Flashcards
What do interleukins consist of
33 different constituent members
What do interleukins regulate
- Normal and malignant cell growth
- All aspects of immune response
- Regulation of inflammation
Interleukin 2 (IL-2)
- Aka T-Cell growth factor
- First T-Cell growth factor to be identified
- Produced exclusively by T-lymphocytes in response to antigen stimulation
- Role in the immune response
Structure of IL-2
- Single chain glycoprotein
- Contains 133 amino acids
- Globular structure - consists of 4 a helical structures and no b conformation
Function of IL-2
- Acts as a central autocrine growth factor for T cells - magnitude of t cell response dependant on IL-2 production
- growth factor for activated B lymphocytes
- stimulates enhanced antibody production and secretion
- Promotes the growth and differentiation of NK cells to form lymphokine activated killer cells.
How was IL-2 produced before recombinant DNA technology?
produced by transformed cell lines - Jurkat leukaemia cell line
How is large-scale IL-2 production achieved today?
heterologous expression against and E. coli background
Recombinant IL-2 preparation
Tradename: Proleukin
Manufactured by: Chiron
how does Proleukin differ from IL-2
non-glycosylated
lacks N-terminal alanine
cys 125 residue has been replaced by a serine
Yet they display same bio activities
What is the significance of IL-2 in cancer treatment?
- Experiments in the 1980s showed that lymphocytes incubated with IL-2 could kill a range of cancer cell lines, including melanoma and colon cancer.
- IL-2 stimulated NK cells (LAK) mediate cancer cell destruction.
How is IL-2 used to promote tumour regression in cancer patients?
- LAK cells purified from a patient’s blood and activated with IL-2 in vitro
- Reintroduced into the patient along with more IL-2.
- Complete tumour regression in 10% of patients with melanoma or renal cancer
- Partial regression in 10-25% of such patients.
What are tumour-infiltrating lymphocytes (TILs)?
- IL-2 stimulated cytotoxic T cells
- Cytotoxic T-lymphocytes that specifically bind to the tumour antigen - tumour-specific cells.
- These cells can be isolated from a tumour biopsy and further activated with IL-2 in vitro.
How effective is IL-2 treatment in promoting tumour regression in cancer patients?
- Further activation of TILs with IL-2, followed by reintroduction into the patient along with more IL-2, promotes tumour regression in >50% of treated patients.
- Additional cancer types, such as ovarian and bladder cancer, non-Hodgkin’s lymphoma, and acute myeloid leukemia, have also shown partial responsiveness to IL-2 treatment.
What are intracellular pathogens?
microbial pathogens that replicate within host cells.
Why are intracellular pathogens difficult to treat?
- They hide within host cells and evade the immune system.
- They can also develop resistance to antibiotics.
What are some examples of intracellular pathogens?
- Mycobacterium tuberculosis
- Listeria monocytogenes
- Legionella pneumophila.
What type of immune response is raised against intracellular pathogens?
Largely a T-cell response.
How might IL-2 be useful in the treatment of intracellular pathogens?
IL-2’s ability to stimulate T-cells renders it useful
What medical conditions are caused or exacerbated by the immune system itself?
- Autoimmune diseases
- Tissue/organ transplantation rejection
How is selective immunosuppressant activity achieved in idividuals suffering with autoimmune diseases or organ rejection?
By preventing the synthesis or functioning of IL-2
example of immunosuppressive for IL-2
Cyclosporin A
- One of the foremost immunosuppresive agents currently in use
- Functions by preventing IL-2 synthesis
What are alternative approaches to IL-2 targeted immunosuppression?
- Soluble IL-2 receptor that competes with native receptor for binding of IL-2
- IL-2 varients that retain the ability to bind but fail to initiate signal transduction
- Monoclonal antibodies that block IL-2 binding
What are some examples of monoclonal antibodies that are capable of blocking IL-2 binding?
Zenapax and Simulect
Interleukin-1 (IL-1)
- also known as lymphocyte-activating factor (LAF)
- endogenous pyrogen
- catabolin
Forms of IL-1
two distinct forms: IL-1α and IL-1β.
What cells produce IL-1
a wide range of cells, in varying ratios.
What is the structure of IL-1α and IL-1β?
- Globular proteins
- Composed of 6 strands of antiparallel β pleated sheets.
- Only 20% aa sequence identity but both bind to the same receptor & induce similar biological activities.
IL-1 biological activities
- Proinflammatory cytokine - promotes synthesis of substances involved in generating inflammatory mediators.
- Role in activating B-Lymphocytes
- Synthesis of acute-phase proteins in hepatocytes with IL-6
- Acts as co stimulator of haematopietc cell growth/differentiation
IL-1 receptor antagonist (IL-1Ra)
- Third IL-1-like protein
- binds to IL-1 receptor without triggering an intracellular response
Acute-phase proteins (APPs)
an evolutionarily conserved family of proteins produced mainly in the liver in response to infection and inflammation.
Approaches to modulating IL-1 activity
- Anti-IL-1 antibodies
- Soluble IL-1 receptor
- The native IL-1 receptor antagonist (IL-1Ra)
IL-1 mediated condition
Rheumatoid arthritis
characterised by the presence of high levels of IL-1 in the synovial fluid of affected joints
Additional negative influences of IL-1
Cartilage degradation and bone resorption
Recombinant form of IL-1Ra for treating rheumatoid arthritis
Kineret
Kineret
approved product for treating rheumatoid arthritis based on IFN-1Ra
How does kineret differ from native form
- Non-glycosolated
- Contains an additional N terminal methionine residue
Additional approach to IL-1 down regulation
inhibiting the proteolytic enzymes that realease the active interleukin fromits native inactive precursor
Example of additional approach to IL-1 down regulation
IL-1b converting enzyme (ICE) which releases active IL-1b from its precursor
What produces Interleukin 11 (IL-11)
IL-1 activated bone marrow stromal cells (connective tissue cells) and fibroblasts (stroma synthesising cells)
Function of IL-11
Haematopietic growth factor
Stimulates:
- growth/differentiation of bone marrow cells
- Thrombopoiesis
What is Neumega?
- Tradename of an IL-11-based product that has been approved for the prevention of thrombocytopenia.
- It works by stimulating platelet production and can partially offset the damage caused by chemotherapy.
