Immune System and Function

Immune System Overview

  • An animal's immune system protects against:
    • Bacteria
    • Viruses
    • Parasites
    • Cancer cells
  • Present in several animal groups, notably vertebrates.
  • Comprised of non-specific and specific defense mechanisms.

Non-Specific Defense Mechanisms

  • Barrier Mechanisms:
    • Skin acts as a physical barrier to pathogens.
    • Chemical barriers include:
    • Perspiration
    • Skin oil
    • Saliva
    • Tears
  • Ciliary Escalator:
    • Cilia and mucus in respiratory tracts that clear dust and debris.
  • Inflammatory Response:
    • Dilation of blood vessels
    • Accumulation of white blood cells (WBCs) at injury sites leading to redness, heat, swelling.
  • Fever:
    • Increased body temperature to inhibit pathogen growth; induced by the body, not germs.

Specific Defense Mechanisms

  • Effective against specific pathogens involving different types of WBCs called lymphocytes (specifically B-cells and T-cells).
    • B-cells:
    • Originates in bone marrow, develops there, and produce antibodies upon exposure to foreign antigens.
    • T-cells:
    • Originates in bone marrow, matures in the Thymus, respond to invaders within host cells, reacts to foreign matter (e.g., organ transplants).
Types of T-cells:
  1. Cytotoxic T-cells: Directly kill pathogens.
  2. Helper T-cells: Assist B-cells and other T-cells; HIV targets and kills these cells.
  3. Suppressor T-cells: Regulate immune response to prevent overreaction.
Antibodies:
  • Proteins in blood plasma and lymph that target bacteria and viruses.
  • Daughter cells of B-cells produce the same antibodies as the original B-cell.
  • Bind to specific areas of antigens, marking them for destruction by T-cells.

Immunity Types

  • Active Immunity:
    • Body produces its own antibodies; can develop through illness or vaccination (permanent).
  • Passive Immunity:
    • Antibodies come from an external source; examples include:
    • Placenta
    • Mother's milk
    • Certain immunizations (e.g., Rhogam shots).
Vaccinations:
  • Weakened/inactive pathogen introduced to stimulate immune response; first seen with Edward Jenner and cowpox to prevent smallpox.

Nutritional Support for Immune System

  • Important vitamins and minerals:
    • Vitamins A, C, E: Known as anti-cancer vitamins, essential for immune function.
    • Minerals: Zinc (Zn), Selenium (Se) support immune health.
  • Foods rich in these nutrients:
    • Dark leafy greens (broccoli, kale)
    • Orange vegetables (carrots).
  • Research shows that higher intake of vitamin C improves T-cell health in AIDS patients.

Acquired Immunodeficiency Syndrome (AIDS)

  • Caused by a virus that kills helper T-cells, weakening the immune response.
  • Transmission via blood-to-blood contact, sexual activity, sharing needles, and from mother to baby during pregnancy.
  • AIDS tests detect anti-AIDS antibodies indicating prior exposure to the virus.

Autoimmune Responses

  • Immune system erroneously attacks its own cells and tissues.
  • Example: In myasthenia gravis, the immune system destroys acetylcholine, crucial for nerve impulse transmission.

Cancer and the Immune System

  • Genetic changes in cancer can make tumor cells less recognizable to the immune system, allowing them to multiply before being attacked.

Allergic Reactions

  • Abnormal immune response to allergens (e.g., pollen, dust).
  • Mechanism:
    • Antibodies bind to mast cells, produce histamine.
    • Effects include sneezing, mucus overproduction, and rashes.
  • Antihistamines: Compete with histamine for receptor sites, reducing symptoms.
  • Newer treatments like mast cell inhibitors prevent histamine production outright.