Immunity

• Plants have internal and external immunity.
• Immune System


  recognizes foreign bodies and responds with the production of immune cells and proteins
• Two types of innate response:

  • innate immunity (all animals)
  • adaptive immunity (for vertebrates only)
• Innate Immune Response

  • present before any exposure to pathogens
  • effective from the time of birth
  • involves non-specific responses
  • has external barriers and chemical defenses
• Adaptive Immune Response

  • "acquired immunity"
  • develops after exposure to foreign substances
  • involves very specific responses to pathogens
• Pathogens


  disease-causing organisms
• Innate Immunity Response

  • barriers
  • phagocytic cells
  • natural killer cells
  • antimicrobial peptides or proteins
  • inflammatory response
• Barrier defenses include skin and mucous membranes.
• Mucous membranes are found in respiratory, urinary, and reproductive tracts.
• In mucous membranes, mucus traps and allows for the removal of microbes.
• Saliva, mucus, and tears are hostile to many microbes.
• Low pH of skin and digestive system prevent the growth of many bacteria.
• Pathogens entering the mammalian body are subject to phagocytosis.
• Phagocytic cells recognize groups of pathogens by TLRs.
• TLRs means toll-like receptors.
• TLRs include TLR3, TLR4, and TLR5.
• TLR3


  sensor for double-stranded RNA; a form of nucleic acid characteristic of certain viruses.
• TLR4


  recognizes lipopolysaccharide, a type of molecule found in the surface of many bacteria.
• TLR5


  recognizes flagellin, the main protein of bacterial flagella
• TLR3 (double-stranded RNA)

  TLR4 (lipopolysaccharide)

  TLR5 (flagellin)
• Different types of phagocytic cells

  • neutrophils
  • macrophages (big eaters)
  • dendritic cells
  • eosinophils
• neutrophils

  • circulates in the blood
  • engulfs and destroys pathogens
• macrophages

  large phagocytic cells in the organs that are common to encounter pathogens
• dendritic cells


  populate tissues like the skin that have contact to the environment
• natural killer cells

  • circulate throughout the body
  • detect abnormal cells
  • release chemicals, leading to cell death
• antimicrobial peptides or proteins


  attack pathogens or impedes their reproduction
• Interferon protein provides innate defense, interfering with viruses and helps activate macrophages.
• Pain and swelling is caused by molecules released upon injury or infection.
• Mast cells (connective tissue) release histamine, which triggers the blood vessels to dilate and become more permeable.
• Activated macrophages and neutrophils release cytokines.
• Pus


  a fluid rich in white blood cells, dead pathogens, and cell debris from damaged tissues
• Pus


  sign that a wound is infected or your body is trying to fight the infection and heal the injury
• Inflammatory can be either local and systemic (throughout the body).
• Fever is a systemic inflammatory response triggered by pyrogens.
• T cells (memory cells) - found in thymus

  B cells (helper cells) - found in the bone marrow
• Adaptive Immunity

  • receptors provide pathogen-specific recognition
  • relies on two types of lymphocytes or white blood cells
• antigens


  substance that can elicit a response from a B or T cell
• B and T cell have receptor proteins that can bind to foreign molecules.
• There are 100,00 antigen receptors on the surface of a single B or T cell.
• Types of T cells

  • cytotoxic T cells
  • helper T cells
  • regulatory T cells
  • memory T cells