Innate and Adaptive Immunity Study Notes (Ch 15 pt 2)

Overview of the Course and Innate Immunity

  • Final Exam: Scheduled for Mon 4/28 from 10:30 AM to 12:30 PM in Floyd 252. 125 points, cumulative. Focus will be on chapters 15, 16, 18, 25, and recent readings.

Components of Innate Immunity

  • Innate Defenses: Include physical, microbiota, and chemical barriers.

    • It’s fast but nonspecific

Physical Barriers

  • Examples:

    • Skin: Protects internal body from environmental microbes, composed of tightly packed epithelial cells.

    • Mucous Membranes: Present in digestive, respiratory, and urinary tracts; provide moist surfaces that can trap pathogens.

    • Respiratory Tract: Nasal hair traps larger particles, mucus and cilia move pathogens out.

  • Functionality of Skin:

    • Approx. 21 sq ft per person, comprising 15% of body weight.

    • Constantly sloughs off dead cells; outer layer is waterproof.

    • Slightly acidic, which helps prevent pathogen growth.

  • Barriers in Mucous Membranes:

    • Rich in bacteriophages and enzymes which help prevent infection. Examples of actions include:

    • Blinking removes irritants from eyes.

    • Saliva carries microbes to stomach.

Chemical Barriers

  • Key Chemicals:

    • Lysozyme: Found in tears and saliva, destroys bacterial cell walls.

    • Acidic Environment: Low pH in stomach and skin deters microbial growth.

Resident Microbiota

  • Contributes to defense by blocking pathogens from attaching to epithelial surfaces and competing for nutrients.

  • Training: Helps to keep commensal organisms in check and eliminating pathogens.

    • Commensal organisms are microorganisms that reside in or on a host organism without causing harm. They are part of the normal flora, especially in areas such as the gut, skin, and mucous membranes. These organisms play a significant role in maintaining the host's health by: - Competing with pathogens for resources and attachment sites, helping to prevent infections. - Contributing to the development and training of the host's immune system, ensuring a balanced response to pathogens. - Participating in metabolic processes, such as digestion in the case of gut microbiota. Overall, commensal organisms contribute to the host's homeostasis and help protect against potential pathogens.

Second Line of Innate Defense

  • Components:

    • Phagocytosis: Process of engulfing pathogens by white blood cells (e.g., neutrophils, macrophages).

    • Inflammation: Signs include redness (rubor), heat (calor), swelling (tumor), and pain (dolor).

    • Fever: A systemic response to infection that may inhibit microbial growth and enhance immune function.

    • Antimicrobial Products: Include interferons and complements which help to destroy pathogens.

Phagocytosis

  • Steps:

    1. Chemotaxis: Movement of phagocytes toward pathogen.

    2. Ingestion: Engulfment of pathogen.

    3. Phagolysosome Formation: Fusion of engulfed material with lysosomes.

    4. Destruction: Breakdown of pathogens using enzymes.

    5. Excretion: Removal of waste material.

Functions of Inflammation

  • Mobilizes immune components and begins repair processes on tissue damage.

  • Helps clear harmful substances and destroys invading microbes by increased blood flow, causing redness, warmth, swelling, and pain.

Fever

  • Characteristics:

    • Elevated body temperature due to infection.

    • Ranges from mild (100-101°F) to high (104-106°F).

  • Benefits:

    • Impedes multiplication of microbes by utilizing heat-sensitive responses.

    • Enhances the activity of immune cells.

Adaptive Immunity

  • Consists of specific responses that are more acute and take longer to develop (3-7 days) and involves B and T cells.

  • Antigens: Markers recognized by the immune system, capable of stimulating an immune response.