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. 
• Antigens are found on pathogens but also on the surface of red blood cells. Although we usually draw cells as smooth blobs, they actually all have bits sticking out of their membranes.
• Antigens are your body’s way of telling which cells are your own, and which cells are unwanted invaders.  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. ​
• physical barriers - Skin​

  Mucous membranes and mucous​

  Earwax ​

  Ear hairs.

  eyelashes.

  nose hairs.

  Ciliated cells.

  Body hair.

  Pubic hair protect your vagina.

  Nails.
• chemical barriers

  Enzymes in tears​

  Acid in stomach ​

  Enzyme in saliva ​

  Mucous​

  Antimicrobial peptides in sweat​

  ciliated cells

  Vagina is acidic.

  anti-bacterial proteins and zinc in semen.
• Physical barriers and chemical barriers 

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

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  • Mucous membrane line the gut, airways, and reproductive system. Goblet cells produce thick, sticky mucous to help trap pathogens. ​
• • Physical barriers and chemical barriers Antimicrobial proteins and peptides also help to destroy pathogens and can also be involved in stimulation of the immune system. ​​
  • 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. ​
• What is non-specific immunity? 

  Immunity that aims to protect the body from all pathogens and will respond to tissue damage and anything considered to be non-self.

  It responds in the same way to all foreign substances.
• Non-specific examples: eyelashes, nose hair, hair on the body, Skin and mucous membrane, Phagocytosis, Antimicrobial proteins and lysozymes, Inflammation.
• What is meant by specific Immunity? 

  Antibodies form part of our specific immunity.  

  Protects the body from a specific invader. Acquired immunity that develops with exposure to previously encountered antigens. Specific immune responses can distinguish among different invaders. It is tailored to attack a specific antigen.
• Specific examples- white blood cells, Antibody mediated, Cell mediated.
• Inflammation – A response to injury or infectionThe area becomes hot, red and swollen as the result of increased blood flow.

  Mast cells respond to tissue damage by secreting histamine. This cell-signalling compounds stimulate a range of responses, including:

  §Dilated blood vessels 

  §Increase blood flow

  §Increase in the numbers of white blood cells  
• How does inflammation protect our body from infection?

  •The inflammatory mediators make it easier for immune system cells to pass out of the small blood vessels, so that more of them can enter the affected tissue.••Swelling prevents the spread of damaging agents to nearby tissues.•• White blood cells swarm the injured area to promote healing.
• How does inflammation protect our body from infection?

  Histamine also stimulates the release of chemicals known as cytokines, including interleukins that lead to more inflammation. The cytokines bring in the body's immune cells, hormones and nutrients to fix the problem. Cytokines also lead to the promotion of phagocytosis
• It takes 7-17 days to produce antibodies.
• Antibodies bind to antigens on the surface of pathogens. Antibodies protect against pathogens in several ways, including:​

  • Binding to toxins produced by bacteria and making them harmless ​
  • Cross-linking pathogens so that they are too large to spread or infect cells​
  • Signalling to phagocytes to engulf the pathogens​
  • Binding to pathogen protein that the pathogens use to enter body cells.​
• Antibodies are proteins. They are produced by the body to fight off foreign antigens.