immunity pt 1

Overview of the Immune System

• The immune system works closely with the lymphatic system.

• White blood cells are crucial to immunity and help in fighting off pathogens, dead cells, and cancerous cells.

• Two broad categories of immunity: innate and adaptive defenses.

Definitions

• Immunity: The ability to resist foreign proteins, viruses, and bacteria, distinguishing between "self" and "non-self."

• Good bacteria: Present in the gut, assisting in digestion but still considered "non-self."

Innate Immunity

Physical Barriers

• Intact Skin: Acts as a mechanical barrier to prevent pathogens from entering the body. Damage like cuts or scrapes can lead to infections.

• Bedsores: Caused by prolonged pressure on certain skin areas, creating openings for pathogens, especially in bedridden patients.

• Skin secretions (sweat/oil) contribute slight acidity (pH around 7.3) preventing bacterial growth.

• Keratin: A protective protein found in skin, hair, and nails; essential for skin barrier function.

• Mucous Membranes: Located in eyes, nose, mouth, and various openings, these membranes secrete mucus to trap pathogens and protect against infections.

  • Dryness caused by conditions like chemotherapy can lead to thrush, especially in uninsured mucosal areas.

  • Importance of gastric juices in maintaining protective barriers against pathogens; sufficient acidity is crucial.

Cellular Defenses

• Phagocytes (e.g., macrophages): Engulf and digest non-self entities.

• Interferons: Proteins released during viral infection; they help protect nearby cells and mobilize lymphocytes.

• Complement Proteins: Assist in lysing bacteria and enhancing phagocytosis.

• Fever: A response to infection that helps raise body temperature to fight off pathogens, often signaling an immune response.

Adaptive Immunity

Specificity and Memory

• Lymphocytes: Key white blood cells involved in adaptive immunity, including specific types for recognizing non-self entities.

• Neutrophils: The most common type of white blood cell, quickly deployed to sites of infection; they phagocytose bacteria and dead cells, but their lifespan is short (about 10 hours in blood).

• Monocytes: Larger white blood cells that develop into macrophages in tissues; they are slower to arrive but can engulf larger particles.

• Adaptive immunity is characterized by memory, allowing the immune system to remember previous encounters with pathogens (e.g., chickenpox).

• Chemotaxis: Movement of white blood cells toward the chemical signals from pathogens.

Inflammatory Response

• Steps in Response to Injury/Infection:

  1. Bacteria invade and cause tissue damage.

  2. Chemical mediators (histamines) are released, signaling to attract more white blood cells to the site.

  3. Increased blood flow enhances permeability, allowing more immune cells to reach the affected area.

  4. If the pathogens are eliminated, tissue begins to repair.

• Importance of taking care of wounds: Without proper care, infections can escalate to sepsis, a life-threatening condition.