Antibodies

• Antigen (antibody-generating): stimulates an immune response; almost any molecule can act as an antigen, but it’s usually a protein/glycoprotein in/on a plasma or internal membrane
• Antibody: protein molecules made by B plasma cells that specifically identify and neutralise antigens; its shape is complementary to their specific antigen; our immune system must make one for every antigen that enters the body
• Specificity: an antibody is specific to a particular antigen due to shape of the variable region of the molecule; each antibody had a differently shaped variable region
• More than one variable region per antibody molecule, allows attachment to more than one antigen (agglutination)
• Generic Antibody structure

  A) antigen

  B) antigen-binding site

  C) antigen in an antigen binding site

  D) disulphide bonds

  E) carbohydrate

  F) heavy

  G) Light

  H) hinge region

  I) Light

  J) disulphide bridge

  K) hinge region

  L) heavy

  M) Variable region

  N) contant region

  O) constant region

  P) Variable region

  Q) light

  R) heavy

  
• Some specific antibody structures

  A) IgM

  B) IgE

  C) IgA

  D) IgD

  E) IgG

  
• Neutralisation


  As pathogens often use their antigens to attach to molecules on the host cells if antibodies attach to these antigens instead, the pathogen is unable to bind to the host cell receptor sites and thus is unable to infect the host cell (antibodies may also bind to toxins produced by the pathogen; these antibodies are called antitoxins)
• Agglutination


  Some are several antibodies joined together, and have several specific variable (complementary) regions; that bind to several pathogens at the same time; the antibody-pathogen complex is too large to enter a host cell
• Opsonisation


  Antibodies make the pathogen more visible to the immune system by marking it non-self, which allows would aid uptake by phagocytes, leading to lysis of the bacterial cell by phagocytic cells
• B lymphocyte response to antigens


  1. Antigen from pathogen or infected cell enters body fluid

  2. Attaches to the complementary antibody on B cell’s surface

  3. B Cell takes antigen in through endocytosis and presents it on its cell surface

  5. T_h Cells bind to antigens and trigger B Cells to divide by mitosis;

  6. Forming plasma cells (produce and secrete antibodies into blood, which work to neutralise pathogen)

  7. Or B memory cells (remember antibody’s specific shape)
• Feature and Functions

  A) antigen

  B) complementary

  C) antigen

  D) amino acid

  E) multiple

  F) antigen

  G) agglutination

  H) Proteins

  I) phagocytes

  J) phagocytosis

  K) junctions

  L) flexibility

  M) four

  N) polypeptide