LESSON 9: Process in Plants and Animals: Immune System

• Immune system


  A complex network that defends organisms against pathogens, recognizing foreign structures and molecules and initiating appropriate immune responses
• Immune system


  • Dysfunction can lead to autoimmune diseases, inflammatory diseases, allergies, and cancer
  • Immunodeficiency results in recurring and life-threatening infections
• Immunity


  The body's ability to resist damage from pathogens and harmful chemicals, including toxins and cancer cells
• Innate immunity


  First line of defense against infections, acts rapidly but lacks specificity and memory, responses do not change from exposure to exposure, provides immediate, nonspecific protection
• Adaptive immunity


  Slower initial response to infections, exhibits memory and specificity, can mount a faster and more effective response upon re-exposure to the same pathogen, pathogens are destroyed before symptoms develop, leading to immunity
• Innate immune system components


  • Barrier defenses (skin, mucous membranes, secretions)
  • Internal defenses (chemical mediators, white blood cells, inflammatory response)
• Types of white blood cells

  • Neutrophils
  • Eosinophils
  • Basophil
  • Monocyte
  • Lymphocyte
• Surface epithelia


  • Produce substances like lysozyme in tears and saliva that fight microbes
  • Tight junctions between epithelial cells create a seal against the external environment
• Acute inflammation


  Triggers the immune response
• Chronic inflammation


  Can cause tissue damage
• Adaptive immune system


  Acquired, involves recognizing specific substances or antigens, distinguishes between foreign antigens and self-antigens
• Humoral response


  Production and secretion of antibodies (immunoglobulins) by B-cells
• Types of antibodies


  • IgM
  • IgG
  • IgA
  • IgE
  • IgD
• Adaptive immune response


  • Triggered by foreign substances found on pathogens, such as proteins, nucleic acids, and sugars
  • Therapeutic agents can be attached to antibodies specific for antigens on cancer cells, minimizing damage to healthy tissue
  • Modern vaccines often contain adjuvants to activate the innate immune response, stimulating B cells to produce antibodies against specific pathogens, establishing memory cells for rapid response upon subsequent infection
• Cell-mediated response


  An immune response that occurs when cytotoxic cells defend the body against microorganisms that live inside the body cells, focuses on handling pathogens that are not easily accessible for antibodies produced by B-cells
• Types of T-cells


  • Cytotoxic T cells
  • Helper T cells
  • Regulatory T cells
• Ways to acquire adaptive immunity


  • Active immunity (natural, artificial)
  • Passive immunity (natural, artificial)
• Invertebrate immune system


  • Lacks adaptive immunity and relies solely on innate immunity, free circulating cells (hemocytes) mediate immune responses, exhibits rapid immune response triggered by peptidoglycan, with subsequent regulation to prevent excessive immune activation and potential harm
• Plant immune system


  • Has innate immune systems and transitions between growth and defense modes, relies on a generic, nonspecific response to infections, possesses immune capabilities through pattern-triggered immunity (PTI) and effector-triggered immunity (ETI), exhibits a remarkable strategy of balancing growth and defense by powering down their immune systems during periods of active growth and in response to changes in environmental conditions, their immunity is also influenced by the plant's microbiota
• Plants possess diverse chemical defenses against bacteria, fungi, worms, and insects, these organic compounds, produced as secondary metabolites, do not hinder normal growth and development
• Duke University researchers discovered that plant cells have a mechanism for selectively activating defensive genes only when pathogens are present, and by applying this knowledge, they engineered plants like Arabidopsis and rice to rapidly respond to infections without constantly being in defense mode
• This breakthrough could lead to plants being naturally resistant to pathogens and reducing the need for pesticides, however, further research is needed to determine if this approach is applicable to other plant species
• INTERNAL DEFENSES - these are the body’s defense systems that consist of: Examples:• Chemical mediators (interferons, complement system).• White blood cells (phagocytes, natural killer cells).

  • Inflammatory response: Fever, redness, swelling, pain, loss of function.
• BARRIER DEFENSES - these are the body’s most basic defense mechanisms that prevent pathogens and any chemicals from entering.

  Examples:

  • Skin and mucous membranes

  • Secretions like tears, saliva, and urine.
• Neutrophils - Most abundant type of white blood cell and the first responder to microbial infection.
• Eosinophils - Primary response to the large multicellular parasites (e.g. helminth infections). Do not phagocytose pathogens but instead release chemical products which perforate cell membranes.
• Basophil - Chiefly responsible for initiating inflammatory responses by releasing the chemicals, "histamine" and "heparin." Promote inflammation as they are the common contributors of allergic responses.
• Monocyte - They are slower to respond than neutrophils but are longer lasting. It differentiates into two types of cells in response to pathogenic infection macrophages (remain in the tissue and phagocytose) and dendritic cells (present antigen fragments to lymphocytes).
• Lymphocyte - Responsible to produce antibodies which target specific antigens present on pathogens. They are more common in the lymphatic system than blood.
• • IgM first antibody to appear in the response to initial exposure to an antigen
• • IgG major antibody produced
• • IgA the important antibody for the mucosal immune response
• • IgE associated with allergic reactions
• 1. IgD - a class of antibodies present as an antigen receptor on most cell surfaces and predominant on human B cells.
• • ACTIVE IMMUNITY Immunity is provided by the individual's own immune system.
• 1. NATURAL ACTIVE IMMUNITY - Antigens are introduced through natural exposure.
• • ARTIFICIAL ACTIVE IMMUNITY Antigens are deliberately introduced in a vaccine
• • PASSIVE IMMUNITY Immunity is transferred from another person or an animal
• 1. NATURAL PASSIVE IMMUNITY - Antibodies from the mother are transferred to her child across the placenta or in milk
• • ARTIFICIAL PASSIVE IMMUNITY Antibodies are produced by another person or an animal are injected