Microbio study

Innate (Non-Specific) Immunity

  • Overview: Innate immunity is the body's first line of defense against pathogens, not specific to any particular pathogen.

Skin and Mucous Membranes

  • Mechanical Protection:

    • Skin: Serves as a physical barrier with multiple layers (epidermis).

    • Mucus: Traps pathogens in the respiratory and digestive tracts.

    • Tears & Saliva: Flush pathogens away, containing antimicrobial properties.

    • Nose: Hair filters inhaled air.

    • Ciliary Escalator: Ciliated cells in the respiratory tract help remove trapped pathogens.

    • Urethra: Aids in flushing pathogens from the urinary tract.

  • Chemical Protection:

    • Sebum: Contains fatty acids with inhibitory effects on microbial growth.

    • Perspiration: Contains lysozyme, an enzyme that attacks bacterial cell walls.

    • Gastric Juice: Highly acidic, kills most ingested pathogens.

Phagocytosis

  • Process of Phagocytosis:

    • Chemotaxis: Movement of phagocytes towards chemical signals from pathogens.

    • Adherence: Bacterium attaches to membrane extensions (pseudopodia).

    • Ingestion: Formation of a phagosome as the bacterium is engulfed.

    • Digestion:

    • Phagosome fuses with lysosome to form a phagolysosome.

    • Lysosomal enzymes digest the pathogen, and products are released from the cell.

Inflammation

  • Phases of Inflammation:

    • Vasodilation: Increased blood flow to the affected area.

    • Increased Permeability: Allows protein and fluid to leave the blood stream, leading to swelling.

    • Phagocyte Migration:

    • Leukocytes respond to chemical signals and migrate to the site of infection.

    • Phagocytes consume pathogens and debris.

    • Repair: Healing of affected tissues begins.

Fever

  • Causes: Triggered by pyrogens such as bacterial toxins and phagocyte secretions.

  • Effects:

    • Induces chills and shivering due to vasoconstriction.

    • Increases metabolic rate, inhibits pathogen growth, and enhances phagocytosis and tissue repair.

    • Ends with perspiration, vasodilation, and a decrease in metabolic rate.

Adaptive (Specific) Immunity

  • Definition: The ability of the body to specifically counteract foreign organisms (antigens).

Types of Immunity

  • Naturally Acquired Active Immunity: Immunity developed through natural exposure to an antigen.

  • Naturally Acquired Passive Immunity: Antibodies passed from mother to child (e.g., through breast milk).

  • Artificially Acquired Active Immunity: Immunity obtained through vaccination.

  • Artificially Acquired Passive Immunity: Receiving antibodies through medical interventions (e.g., antivenom).

  • Herd Immunity: Protection of a population when a significant portion is immune, reducing the spread of disease, even among non-immunized individuals.

The Immune Response

  • Process:

    1. Recognition: The immune system identifies invaders as foreign substances.

    2. Immune Activation and Response:

    • Specific B cells are activated through clonal selection.

    • Clones of activated B cells differentiate into:

      • Plasma Cells: Produce specific antibodies.

      • Memory Cells: Provide immunologic memory for faster future response.

Antibody Response

  • Primary Response:

    • First exposure to a specific antigen; more time needed to mount a response.

    • IgM is produced initially, followed by IgG.

  • Secondary Response:

    • Subsequent exposure to the same antigen leads to a more rapid and robust response due to memory cells.

    • Higher levels of IgG are produced more quickly.