Introduction to the Human Immune System

Overview

• The human immune system is extremely complex, second only to the human brain.
• Functions as a defense against microorganisms and cancerous cells.
• Consists of hundreds of small organs and two large ones, forming a transport network throughout the body.
• Produces billions of new cells daily, organized like an army.

Immune System's Role

• Protects the body from billions of microorganisms that cause disease.
• Involves essential cells acting as soldiers, captains, and officers.
• Constantly active in defense and surveillance.

Initial Response to Infection

• Example Scenario: Cut on thumb introduces bacteria.
  • Cells release chemical alarm signals upon injury.
• First Responders: Macrophages and Neutrophils.
  • Macrophages: Large cells that devour up to 100 bacteria each.
  • Neutrophils: Aggressive suicide warriors targeting bacteria.
    • Release toxic chemicals, can explode to trap bacteria.
    • Cause collateral damage, resulting in inflammation (e.g., swelling, redness).
• Inflammation: Blood vessels allow fluid/generating inflammation to bring complement proteins which attack bacteria.

Escalation and Reinforcements

• When first responders are overwhelmed, dendritic cells act as intelligence officers.
  • Dendritic Cells: Collect and present bacterial parts to Helper T cells.
• Helper T Cells: Commanders that recognize bacterial parts and activate appropriate responses.
  • Clone into thousands upon activation.
  • Activate or revive exhausted macrophages with chemical signals.

Heavy Weaponry: B Cells and Antibodies

• B Cells: Activated by Helper T cells, they produce antibodies.
  • Antibodies: Target specific bacteria, neutralizing them and aiding in their destruction.
  • Massive production rate by B cells (up to 2,000/second).
• Post-Battle: Some Helper T and B cells become memory cells for long-term immunity.

Immune Memory

• Memory cells remain vigilant against the same bacteria in the future.
• Provides lasting immunity to specific pathogens.

Conclusion

• The battle inside the body happens daily to keep us safe.
• This lecture is just the beginning of understanding the immune system's complexity.
• Further detailed information can be found in the book "Immune" by Phillip Dettmer.

Additional Resources

• Book: "Immune: A Journey into the Mysterious System that Keeps You Alive" by Phillip Dettmer.
  • A comprehensive and illustrated guide on the immune system.
  • Available for pre-order and recommended for a deep dive into the topic.