Antigens and phagicytosis

• ANTIGENS

  molecules that generate an immune response when detected by the body found on the surface , including all body cells. Antigens not normally found in the body are called foreign antigens.
• Antigens are able to identify:

  • Pathogens
  • Abnormal body cells
  • Toxins
  • Cells from other individuals of the same species
• Pathogens

  •  microorganisms that cause disease, e.g bacteria, virus and fungi, all pathogens have antigens on their surface identified as foreign antigens by immune system cells, which then respond to destroy the pathogen.
• Abnormal body cells

  • cancerous or pathogen infected cells have abnormal antigens on their surface, triggering an immune response
• Toxins

  •  these are poisons, are molecules not cells. Produced by bacteria and the immune system can respond to these toxins as well as the pathogens that release them
• Cells from other individuals of the same species

  • when you receive cells from another person, e.g organ transplant or blood transfusion, the cells will have antigens different to your own. The foreign antigens trigger an immune response, this response leads to the rejection of transplanted organs if drugs are not taken ro suppress the recipient immune system.
  • For blood transfusions, the most important antigens are the ABO blood group antigens, if donated blood contains A or B antigens that aren't recognised by the recipient's immune system, they will generate an immune response.
• phagocyte

   type of blood cell that carries out phagocytosis. They Are found in the blood and tissues and are the first cells to respond to an immune system trigger inside the body.
• Phagocytosis – the process by which phagocytes ingest and destroy pathogens.
• Phagocytosis:

  1. The phagocyte is attracted by the pathogen’s(chemoattractants) . follows the concentration gradient so moves towards pathogen.
  2. The phagocyte has several receptors on cell surface membrane that recognize, attach to chemicals on surface of pathogens.
  3. They engulf the pathogen to form a vesicle, phagosome.
  4. Lysosomes move towards phagosome and fuse with it
  5. Enzymes called lysozymes are present in lysosomes, these destroy ingested bacteria by hydrolysis of their cell walls.
  6. Soluble products from breakdown of pathogen are absorbed into cytoplasm of phagocyte.
• Phagocytosis / physical barriers


  Non specific immune response