E

Immune System and Exercise

Body Recognition of Foreign Agents

  • The body uses thumbprints (MHC - Major Histocompatibility Complex) to identify what belongs and what doesn't.
  • Foreign bodies without the correct MHC are recognized as threats, prompting an immune response.

Phagocytes: The Pac-Man of the Immune System

  • Phagocytes, particularly macrophages, engulf foreign bodies that do not match the body’s MHC.
  • Once engulfed, enzymes within vesicles break down the foreign material into residual bodies.
  • Residual bodies are processed and eliminated by the kidneys and liver.

Types of Phagocytes

  1. Neutrophils
    • Act as the first responders to tissue damage or infection.
    • Arrive at the injury site within an hour to clean up.
    • They release cytokines to attract more immune cells.
  2. Macrophages
    • Migrate to the site after neutrophils have initiated cleanup.
    • Responsible for serious repair and cleanup of damaged tissues.
    • Considered as the "physician" of the immune system.

Cytokines and Immune Response

  • Cytokines serve as chemical messengers in the immune system, signaling the need for more immune cell support at sites of damage.
  • They attract neutrophils and macrophages to sites of injury through signaling pathways.
  • Increased blood flow (vasodilation) is critical for bringing immune cells to the affected area, which causes swelling.

Inflammation

  • Acute Inflammation
    • Characterized by localized redness, heat, swelling, and pain; typically resolves in a few days after injury.
  • Chronic Inflammation
    • A persistent state where the immune system remains activated, often leading to continuous tissue damage (e.g., COPD).
  • Symptoms of Inflammation
    • Redness and heat result from vasodilation; swelling is due to increased capillary permeability allowing fluid and cells to enter tissue, causing pressure on nociceptors leading to pain.

Types of Immune Responses

  • Innate Immunity
    • The body's immediate response to foreign pathogens. Includes neutrophils and macrophages.
  • Acquired (Adaptive) Immunity
    • Learns and remembers pathogens for future protection, involving B cells (which tag pathogens) and T cells (which destroy infected cells).

B Cells and T Cells

  • B Cells
    • Produce antibodies to tag pathogens for destruction without directly killing them.
  • T Cells
    • Kill infected cells and are activated by the presence of antibodies on infected cells.
  • Natural Killer Cells
    • Destroy compromised host cells and act similarly to T cells but with differing activation mechanisms.

Organ Donation and Immune Response

  • Organ transplant success often requires immunosuppressants to prevent the immune system from attacking the foreign tissue, which maintains functionality while protecting from infections.
  • The immune system has a memory that eventually learns to tolerate the new tissue as non-threatening.

Exercise and the Immune System

  • Moderate exercise boosts immunity and decreases the risk of infections, while excessive high-intensity exercise can lead to immunosuppression due to muscle damage.
  • Regular moderate intensity exercise enhances immune response and reduces susceptibility to illnesses.

Open Window Theory

  • After intense exercise, the immune system is temporarily less effective (open window) as immune cells are diverted to recover damaged muscle tissue.
  • The duration of this open window lasts about 3-4 hours post moderate exercise; stretches longer in cases of excessive physical stress.

Practical Recommendations

  • During Illness: Exercise is generally safe for mild symptoms (above the neck). For more severe symptoms (below the neck), rest is advised.
  • Exercise for Immunocompromised Individuals: Low to moderate intensity activity can be beneficial, but high intensity exercise is discouraged to prevent further immunosuppression.