5.5 antibodies

Protein with specific bonding sites synthesised by B cells. When the body is infected by non self material, the B cell produces a specific antibody

. The specific antibody reacts with an antigen on the surface of non self material . Each antibody has two identical binding sites, and these sites are complimentary to a specific antigen

Because they’re made out of proteins which can have many different sequences of amino acids so have an almost infinite number of forms

. Two pairs so 4 peptide chains- . where one pair have long chains so are called heavy chains . One pair have short chains so are called light chains

Antigen-antibody complex As each antibody has a specific binding site that fits precisely onto the specific antigen

It’s a variable region because it is a different shape on different antibodies The constant region is the rest of the antibody which binds to receptors on cells eg B cells It’s made of a sequence of amino acids that form a 3D shape

. Antibodies don’t destroy antigens, but they prepare it for destruction .Agglutination of the bacterial cells: Clumps the bacterial cells together making it easier for the phagocytes to locate them as they’re less spread out within the body . They serve as markers that stimulate phagocytes to engulf the bacterial cells to which they are attached

It’s shaped like a Y . The two top chains are the light chains, and on the top of those are the antigen binding sites and variable region . The bottom chains are the heavy chains and constant regions

. Any microorganism entering the body will have many antigens on it which will each induce a different B cell to multiply and form a clone of itself. The clones will each produce a different antibody, so if one of these antibodies is isolated and cloned outside of the body, it’s monoclonal

. Since an antibody is specific to a particular antigen, monoclonal antibodies can be used to target specific substances and cells eg cancer cells.

. Monoclonal antibodies are produced that are specific to the antigen on cancer cells . These antibodies are given to the patient and attach themselves to receptors on their cancer cells . They attach to the surface of their cancer cells and block the chemical signals that stimulate their uncontrolled growth

It is a monoclonal antibody used to treat breast cancer Since the antibodies are not toxic, and are highly specific, they leave fewer side effects than other forms of therapy

. Attach a radioactive or cytotoxic drug ( a drug that kills cells) to the monoclonal antibody, and when the antibody attaches to cancer cells, it kills them. They are referred to as magic bullets and can be used in smaller doses as they are targeted on specific sites. Using them in smaller doses is cheaper and reduces any side effects the drug may have

. Can diagnose diseases such as influenza, hepatitis, and chlamydia infections where they produce a more rapid result than conventional methods of diagnosis They can also diagnose cancer eg men with prostate cancer often produce more of a protein celled PSA leading to high levels of it in the blood. . By using a monoclonal antibody that interacts with this antigen, you can find the amount of PSA in the blood so if its higher than normal it gives a warning of the possibility of cancer

Pregnancy testing kits can be used at home so pregnancy is detected early. . The placenta produces a hormone called human chorionic gonadatrophin (hCG) which can be found in the mothers urine . Monoclonal antibodies specific to the antigen of hCG are on the test strip and are linked to coloured particles . So if hCG is present it binds to these antibodies and a HCG-antibody-colour complex moves along the strip until it is trapped by a different type of antibody, creating a coloured line

.Making them involves the use of mice, which are used to produce antibodies and tumour cells so cancer is deliberately induced in the mouse which could kill them. . Although monoclonal antibodies can successfully treat many diseases eg cancer, there are also many deaths involved with their use in the treatment of multiple sclerosis. That is why patients must be able to give informed consent . Testing for the drugs present certain dangers eg in one test in 2006, the people suffered organ failure but luckily they all survived

. A mouse is exposed to non self material . So the B cells in the mouse produce many antibodies to fight it, which can be removed from the spleen of the mouse . To enable these B cells to divide outside of the body, they’re fused with tumour cells. . Detergent is added to the mixture to help break down the cell surface membrane of each cell so they fuse together . These make hybridoma cells . Hybridoma cells are separated under a microscope . Clonal selection occurs where a cell is selected that produced the desired antibody, and then cloned and extracted from the growth medium