Recognising non-self cells

• Phagocytosis

  1. Pathogen releases chemicals that attract phagocytes towards it along a concentration gradient

  2. Phagocyte binds to pathogen via complementary receptors

  3. Phagocyte engulfs pathogen, encasing it in a vesicle (phagosome)

  4. Lysosomes combine with phagosome

  5. Lysosomes release lysozymes to break down pathogen through hydrolysis reactions

  6. Soluble products are absorbed by cytoplasm, the insoluble are expelled
• types of non-self cells that lymphocytes can recognise

  • Pathogens
  • Toxins from pathogens
  • Abnormal body cells
  • cells from other humans in transplanted organs
• Define antigen

  A protein in the cell surface membrane that triggers an immune response