4.1 Monoclonal Antibodies Flashcards
What cells produce antibodies?
Plasma cells
What are the 2 main parts of an antibody?
- Antibody binding fragment
2. Fragment crystallisable region
What is the function of the antibody binding fragment?
Recognises antigen. Has hyper variable regions that enable antibodies to recognise a wide range of antigens
What is the function of the fragment crystallisable region?
To interact with cell surface receptors on other immune cells to stimulate the immune system (phagocytosis cells)
How do monoclonal antibodies vary from polyclonal antibodies?
They are monovalent so have the affinity for a single antigen or epitope
How are monoclonal antibodies used in diagnostics?
- Can be used to tag cell surface markers. By adding certain chemicals to the antibody, this tagging can be visualised by the addition of a light signal which can be read by certain machines such as a flow cytometers or due to the reaction with an enzyme such as in immunohistochemistry
- used as the basis of reed blood cell grouping as monoclonal antibodies are used to detect RBC antigens
- used in pregnancy testing as a certain monoclonal antibody can target the antigen pregnancy hormone B-HCG
How have monoclonal antibodies had an impact on therapeutics?
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What are monoclonal antibodies?
Monoclonal antibodies are monovalent antibodies which bind to the same epitope and are produced from a single B-lymphocyte clone
What is the hybrids a technique?
A technique used to produce specific desired colonial antibodies
- The generation of hybridomas involves immunising a certain species against a specific epitope on an antigen and then harvesting the B-lymphocytes from the spleen of the mouse
- The B-lymphocytes are then fused with an immortal myeloma cell line not containing any other immunoglobulin-producing cells
- The resulting hybridoma cells are then cultured in vitro so only the hybridomas (i.e. the fusion between the primary B-lymphocytes and myeloma cells) survive
- Selected hybridomas are found making a specific desired clonal antibody
What are the benefits of monoclonal antibodies?
- specific
- can be targeted against almost any cell-surface receptor
- can be produced in large amounts with ease
What are naked monoclonal antibodies?
Antibodies that work by themselves and have no other drug or radioactive material attached to them
What are murine monoclonal antibodies?
Antibodies derived from another species (mice), not human at all.
What are the disadvantages of murine antibodies?
Recognised by the patients immune system as foreign and rapidly cleared and destroyed
What are chimeric antibodies?
Antibodies that combined region that remained mouse (murine) integrated with areas of the antibody that were human (65%)
What was the advantage of chimeric antibodies over murine?
Chimeric antibodies have the Fc region of the antibody is humanised, the immunogenicity is significantly reduced
What have been the benefits of using fully humanised monoclonal antibodies?
The potential for immunogenicity is much lower
What are antibody drug conjugated?
Conjugated monoclonal antibodies are where a monoclonal antibody is linked to a potent drug to allow targeted delivery of this potent drug as the antibodies bind to tumour specific antigens. This limits the systemic exposure to the cytotoxic agent
ADCs are designed to allow for the use of highly potent, normally intolerable anti cancer cytotoxic agents
What is the mechanism of action of conjugated monoclonal antibodies?
- monoclonal antibodies bind to specific tumour antigens
- monoclonal antibodies have the ability to persist in circulation over time, allowing prolonged exposure to the cancer cells and to become internalised by the cancer cell
- antibody component may be able to prevent signalling by the cancer cell, conduct antibody-dependent cellular cytotoxicity and induct apoptosis
- receptor mediated endocytosis of the cell receptor and the attached monoclonal antibody occurs
- lysosomal degradation of the complex occurs
- release of the potent cytotoxic agent which elicits cell death
How do conjugated monoclonal antibodies target cancers?
target antigens are preferentially or exclusively expressed on the surface of cancer cells, not other cells
What is the role of linkers in conjugate monoclonal antibodies?
- stable linkers conjugate potent cytotoxic agents to monoclonal antibodies. Linker stability in circulation controls the distribution and delivery of the cytotoxic agent to the target cell
What are conjugated monoclonal antibodies used to treat?
Treatment of B cell and T cell lymphoma
What are bispecific monoclonal antibodies?
Utilise the two binding domains of the antibody structure by binding to two different cell populations. This brings the two different cell populations into close proximity with each other
What are bispecific monoclonal antibodies currently being developed for?
To redirect the immune response against cancer cells by binding to the malignant cancer cell and also a the T cell, bringing the 2 different cells closer together. Leads to T cell effector function against the lymphoma cell
What are the 5 different functions of monoclonal antibodies?
- Binding with cell surface receptors to either activate or inhibit signalling within the cell
- Binding to induce cell death
-Binding with cell surface receptors to activate:
• antibody-dependent cell-mediated cytotoxicity (ADCC) or
• complement-dependent cytotoxicity (CDC) - Internalization (ie being taken in by the cell through the membrane) for antibodies delivering toxins into the cancer cell
• Blocking inhibitory effects on T cells (checkpoints). Thus activating T cells to help ‘kill’ the cancer cells
