BSCI 20021: Basic Microbiology Study Notes

BSCI 20021: Basic Microbiology Study Notes

INNATE IMMUNITY

Chapter 11 Overview
  • Focus on innate immunity mechanisms
  • Essential for understanding the body’s first line of defense against infections

NSAIDs (Non-Steroidal Anti-Inflammatory Drugs)

COX Enzymes
  • COX-1:
    • Nature: Constitutive enzyme
    • Role: Involved in normal tissue homeostasis and production of prostaglandins (PGs)
  • COX-2:
    • Nature: Inducible enzyme; can also be constitutive
    • Role: Produces PGs in response to inflammation
Prostaglandins (PGs)
  • Involved in various physiological processes and immune responses
  • Inflammation triggers the synthesis of PGs leading to pain and swelling
Selective COX-2 Inhibitors
  • Developed to reduce inflammation with fewer gastrointestinal side effects associated with traditional NSAIDs
  • Targets conditions such as arthritis and inflammation
Common NSAIDs
  • Examples:
    • Aspirin
    • Ibuprofen
    • Naproxen

Immune Response Mechanisms

Phagocytosis
  • Involves the ingestion of microbes or debris by phagocytic cells (e.g., neutrophils, macrophages)
  • Phagocytosis Steps:
    1. Recognition: Phagocytic cells recognize pathogens through receptors.
    2. Engulfment: Invagination of the membrane forms a phagosome.
    3. Digestion: Phagosome fuses with a lysosome, leading to the destruction of the microbe by lysosomal enzymes.
    4. Signal Activation: Degraded microbial proteins can activate other immune cells, priming the adaptive immune response.
Neutrophils and Macrophages
  • Neutrophils:
    • First responders to infection
    • Quick to arrive at the site (within hours)
    • Perform phagocytosis and release granular enzymes (degranulation)
    • May succumb after a few rounds of degranulation, lifespan around 1-2 days
  • Macrophages:
    • Arrive later at the infection site (typically within 1-2 days)
    • More effective in cleaning up the debris and dead cells
    • Play a crucial role in signaling adaptive immunity by presenting antigens

Resolution of the Innate Immune Response

Phases of Inflammation

  • Resolution Phase:

    • Important for restoring tissue homeostasis
    • Primarily conducted by activated macrophages

  • Process of Resolution:

    1. Blood vessels return to normal state, reducing exudate.
    2. Exudate is drained back into lymphatic vessels.
    3. Tissue structure and function are restored if managed properly.

  • Healing Outcomes:

    • Normal Regeneration:
    • Tissue returns to normal structure with minimal to no scarring.
    • Fibrosis:
    • If the repair process is dysfunctional, excessive connective tissue may form, leading to poor tissue function.

Diseases of Chronic Inflammation

  • Chronic inflammation may result from various conditions, leading to tissue damage and loss of organ function.
  • Examples of Chronic Inflammation Diseases:
    • Atherosclerosis
    • Obesity
    • Stroke
    • Type 2 Diabetes
    • Heart Disease
    • Chronic Obstructive Pulmonary Disease (COPD)
    • Autoimmune Diseases (e.g., rheumatoid arthritis, multiple sclerosis)
    • Cancer and Alzheimer’s Disease
  • Fibrotic Response:
    • Chronic inflammation can lead to excessive fibrosis, impairing normal function and healing processes.

Key Review Points

  • Leukocyte Recruitment: Understand the order of phagocytic cells that arrive at the site of infection, along with their respective strengths and weaknesses (previous study guide).
  • Stages of Phagocytosis: Be familiar with the detailed process of phagocytosis, including recognition, engulfment, digestion, and activation of adaptive immunity.
  • Resolution Phase Flows:
    • Learn how activated macrophages contribute to tissue repair and what factors influence the resolution of inflammation, both in the presence and absence of inflammatory signals.