(5) Antibodies

• antibodies are proteins with specific bindings sites produced by B cells
• antibodies are produced by B lymphocytes - humeral immune response
• when the body is infected by non-self material, a B cell produces a specific antibody
• specific antibodies bind to the antigen on the surface of the non-self material
• each antibody has two identical bindings sites - are complementary to a specific antigen
• a massive variety of antibodies is possible because they are made of proteins
• antibodies are made up of 4 polypeptide chains
• the long chains are called the heavy chains
• the short chains are called the light chains
• each antibody has a specific binding site that fits very precisely into a specific antigen to form what is known as the antigen-antibody complex
• the binding site is called the variable region
• each binding site consists of a sequence of amino acids that form a specific 3D shape
• constant region = same in every antibody
• the constant region binds to receptors on cells such as B cells
• Antibody :

  • made of 4 polypeptide chains
  • 2 heavy chains + 2 light chains
  • 2 binding sites - fits very precisely onto a specific antigen to form antigen-antibody complex
  • variable region - binding site with a sequence of amino acids that form a specific 3D shape
  • constant region - bind to B cell
• antibodies are proteins with specific binding sites produced by B cells
• antibodies do not destroy antigens directly but instead prepare the antigen for destruction
• different antibodies lead to the destruction of an antigen in a range of ways
• Antibodies vs bacteria cells :

  • cause agglutination
  • serve as markers
• Agglutination :

  • Antibodies cause agglutination of the bacterial cells
  • clumps of bacterial cells are formed
  • makes it easier for the phagocytes to locate them
  • less spread-out within the body
• agglutination happens because each antibody has two binding site
• Antibodies as markers :

  • antibodies serve as markers
  • stimulate phagocytes to engulf the bacterial cells
  • Phagocytes move along concentration to a chemical attractant
• • bacterium/ microorganisms entering the body is likely to have hundreds of different antigens on its surface
  • each antigen will induce a different B cell to multiply and form a clone of itself
  • each clone will produce different antibody
• Monoclonal Antibodies :

  • considerable medical value to produce antibodies outside of the body
  • better if a single type of antibody can be isolated and cloned
• Making Monoclonal Antibodies:

  • inject antigen into a mouse (immune response)
  • collect B lymphocytes
  • fuse with myeloma to make hybridoma
  • produce mBAs
• an antibody is very specific to a particular antigen
• as an antibody is very specific to a particular antigen, monoclonal antibodies can be used to target specific substances and specific cells
• monoclonal antibodies can be used to target cancer cells
• Direct monoclonal antibody therapu for cancer :

  • monoclonal antibody are produced that are specific to antigen on cancer cells
  • these antibodies are given to a 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
• herceptin is a monoclonal antibody used to treat breast cancer
• Advantage of using monoclonal antibodies :

  • antibodies are not toxic
  • are highly specific
  • lead to fewer side effects than other forms of therapy eg chemotherapy
• Indirect monoclonal Antibody therapy :

  • attaching a radioactive or cytotoxic drug (a drug that kills cells) to monoclonal antibody
  • antibody attaches to the cancer cells
  • kills the cancer cells
  • smaller doeses used so it is cheaper and theres reduced side effects from the drug
• monoclonal antibodies are also used in diagnosing disease
• monoclonal antibodies are used to diagnose :

  • influenza
  • hepatitis
  • chlamydia
• monoclonal antibodies are used is diagnosing diseases because they produce a more rapid result than convectional methods of diagnosis
• Advantage of using Monoclonal Antibodies for Diagnosing Diseases :

  • rapid
  • cheap
  • accessible
  • painless
  • no infection risk
  • less invasive
• the use of home pregnancy testing kits has made possible the early detection of pregnancy
• when a female is pregnant, the placenta produces a hormone called hCG
• human chorionic gonadotropin (hCG) is a hormone produced by the placenta
• pregnancy kits rely on the fact that the placenta produces hCG