2.4 Antibodies Flashcards
What are antibodies?
Proteins secreted by plasma cells with specific binding sites synthesised by B cells on variable region of light chains have specific tertiary structure complementary to an antigen. The rest of the molecule is known as the constant region
What happens when the body is infected by non-self material?
- A B cell produces a specific antibody.
- Which reacts with an antigen on the surface of the non-self material by binding to them.
- Each antibody has two identical binding sites. The antibody binding sites are complementary to a specific antigen.
- The massive variety of antibodies is possible because they are made of proteins - molecules that occur in an almost infinite number of forms
What is the structure of an antibody?
- Antibodies are made up of 4 polypeptide chains.
- The chains of one pair are long and are called heavy chains, while the chains of the other pair are shorter and are known as light chains.
- Each antibody has a specific binding site that fits very precisely onto a specific antigen to form what is known as an antigen-antibody complex.
- The binding site is different on different antibodies and is therefore called the variable region.
- Each binding site consists of a sequence of amino acids that form a specific 3-D shape that binds directly to a specific antigen.
- The rest of the antibody is known as the constant region. This binds to receptors on cells such as B cells.
How does the antibody lead to the destruction of the antigen?
- Antibodies do not destroy antigens directly but rather prepare the antigen for destruction.
- Different antibodies lead to the destruction of an antigen in a range of ways.
- When the antigen is a bacterial cell:
• They cause agglutination of the bacterial cells. In this way clumps of bacterial cells are formed (formation of antigen-antibody complex), making it easier for the phagocytes to locate them as they are less spread-out within the body.
• They then serve as markers that stimulate phagocytes to engulf the bacterial cells to which they are attached, enhancing phagocytosis
What are monoclonal antibodies?
- Antibodies produced from a single clone of B cells, where each antigen will induce a different B cell to multiply and form a clone of itself.
- Each of these clones will produce a different antibody.
- It is of considerable medical value to be able to produce antibodies outside the body.
- monoclonal antibody - a single type of antibody that can be isolated and cloned
What can monoclonal antibodies be used for? Example?
- Can be used to target specific substances and specific cells
- One type of cell they can target is cancer cells
How can monoclonal antibodies treat cancer?
- The most successful so far is direct monoclonal antibody therapy.
• Monoclonal antibodies are produced that are specific to antigens on cancer cells.
• These antibodies are given to a patient and attach themselves to the receptors on their cancer cells.
• They attach to the surface of their cancer cells and block the chemical signals that stimulate their uncontrolled growth. - An example is herceptin, a monoclonal antibody used to treat breast cancer
What is the advantage of direct monoclonal antibody therapy?
The advantage of direct monoclonal antibody therapy is that since the antibodies are not toxic and are highly specific, they lead to fewer side effects than other forms of therapy.
What is indirect monoclonal antibody therapy?
- It involves attaching a radioactive or cytotoxic drug (a drug that kills cells) to the monoclonal antibody.
- These cancer drugs are therefore delivered directly to the cancer cells and it kills them
- this reduces the harmful side effects that traditional chemotherapy and radiotherapy can produce
Why do we use monoclonal antibodies in small doses?
- its cheaper
- reduces any side effects the drug might have
How do antibodies assist in its destruction?
- They cause agglutination of the bacterial cells. In this way clumps of bacterial cells are formed, making it easier for the phagocytes to locate them as they are less spread-out within the body
- They then serve as markers that stimulate phagocytes to engulf the bacterial cells to which they are attached
What can monoclonal antibodies be used for?
- medical treatment
- pregnancy tests
- medical diagnosis
What is direct monoclonal antibody therapy?
- some cancer can be treated using monoclonal antibodies which are designed with a binding site complementary in shape to the antigens on the outside of the cancer cell
- the antibodies are given to the cancer patient and attach to the cancer cells. While the antibodies are bound to the cancer antigens, this prevents chemicals binding to the cancer cells which enables uncontrolled cell division
- Therefore, the monoclonal antibodies prevent the cancer cells growing, and as they are designed to only attach to cancer cells they do not cause harm to other normal cells
What are the ethical issues with using monoclonal antibodies?
creating monoclonal antibodies requires mice to produce the antibodies and tumour cells, which leads to ethical debates as to whether this use of animal is justified to enable the better treatment of cancers in humans and to detect disease
