Antigen and Antibody

• • Antigens are chemical markers. They are usually proteins or glycoproteins (proteins with sugar molecules attached).​
• • Antigens are recognised by the immune system as self (the body’s own cells) or non-self (foreign cells and pathogens) and stimulates an immune response. ​
• All of your body’s cells have particular shaped antigens sticking out of them.Other cells, e.g. bacteria or viruses, have different shaped antigens from yours, and your body can tell that they don’t belong.​
• Antibody:

  • Molecules which are shaped to fit onto antigens. ​
  • A blood protein that is produced in response to a specific antigen. ​​
  • An antibody binds specifically to antigen in a similar way an enzyme binds to a substrate. ​
• Examples of Physical Barriers:

  Skin​

  Mucous membranes and mucous​

  Hairs in ears ​

  Earwax ​

  Eyelashes

  Hairs protect the vagina
• Examples of Chemical Barriers

  Enzymes in tears​

  Acid in stomach ​

  Enzyme in saliva ​

  Mucous​

  Antimicrobial peptides in sweat​
• Physical And Chemical Barriers:

  The first line of defence is to keep pathogens out. The skin plays a significant role as an external barrier. ​

  ​Mucous membrane line the gut, airways, and reproductive system. Goblet cells produce thick, sticky mucous to help trap pathogens. ​​Antimicrobial proteins and peptides also help to destroy pathogens and can also be involved in stimulation of the immune system. ​
• Physical and Chemical barriers:

  Lysozyme is an enzyme that hydrolyses bonds in the cell wall components of some bacteria. This weakens the cell walls, meaning the bacteria swell and burst. Lysozyme is present in tears, helping to protect the surface of the eyes, as well as in breast milk providing protection to infants while their immune systems are developing. ​