defence, antibodies and antigens


Antigens are molecules which stimulate an immune response. Most molecules can act as antigens. They are large molecules which have specific shapes. If the immune system detects foriegn antigen the relesing of antibodies will begin. One antibody is specific to one antigen, so inly onle one antigen can be used on one pathogen. Antigens are usually made of protiens or glycoprotiens. Anitgens our bodies produce are recognized

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Antibodies are produced by lymphocytes. They are released in response to an infection. They are large protiens also knowns as immunoglobulins. they have a specific shape which is complementary to a particular antigen. Our bodies immune system manafacture one antibodiy for every antigen. once an antibody has attached to an antigen they render them harmless.

antibodies are in a distinctive "Y" shape with 2 distinct regions an antibody is made of;

  • 4 polypeptide chains held by a disulfide bond
  • constant region which is the same shape in all antigens
  • variable region which differs for each antibody- result of amino acid chain
  • hinge region which allows certain movement


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antibodies continued

They work by attaching to antigens on the pathogen.the pathogen may have another use for the pathogen - may be a binding site

They are produced as response to infection. it may take up too 7 days before the number in the blood rises to a level that can successfully combat the infection. this is known as Primary immune response. once pathogen has been dealt with the number of antigens drops. if the same infections attacks the body again the antibodies are made again. the production of antibodies starts concentration rises quicker.

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Primary Defences

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Secondary defence

Phagocytes kill pathogens before they can multiply and damage the body.

  • Neutrophils are the most common phagocytes. They have multi lobed nucleus and are manufactured in bone marrow. they travel around the blood. They're short lived but will be released in large numbers in case of infections
  • Macrophages are larger and manufactured in bone marrow. commonly found in lymph nodes. they engulf infections and then display the antigens.

Phagocytes work because they engulf and destroy pathogens. pathogens are noticed by antigens on its membrane. Antibodies attach to foriegn antigens. the receptor binds to antibodies.

infected cells release histamine which attracts neutrophils. this may cause swelling. Macrophages play an important role in specific response to disease - immune response. which is an activiation of lymphocytes in the blood to help fight disease

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