Immune System Overview

Introduction to the Immune System

• The immune system is crucial for defending the body against foreign agents, such as viruses and bacteria.
• Two main types of immunity: acquired immunity and innate immunity.

Acquired Immunity

• Acquired immunity develops over time through exposure to pathogens.
• Not present at birth; it matures as the body encounters various foreign agents, such as viruses (e.g., flu virus) and bacteria (e.g., strep).
• Important during COVID, highlighting the need for hospitals to manage high levels of infections due to inadequate immunity at birth.
• Learning Process: The body remembers previous infections, allowing for stronger responses to subsequent exposures.

Innate Immunity

• Innate immunity is the body’s first line of defense against pathogens and is present at birth.
• Provides external protection:
  • Physical barriers, such as skin and mucous membranes, prevent pathogens from entering vital organs.
• Provides internal protection:
  • Specialized immune cells: phagocytes, natural killer cells, neutrophils, etc.
  • Each cell type has a distinct function in targeting and eliminating harmful cells.

Specialized Immune Cells

• Phagocytes: Cells that engulf and digest foreign particles.
• Natural Killer Cells: Target and destroy infected or cancerous cells.
• Neutrophils: A type of white blood cell that responds rapidly to sites of infection.

Complement System

• Part of innate immunity; helps detect and tag foreign bodies.
• Function:
  • Identifies bacteria and other pathogens by marking them with protein tags (red flags) that signal for destruction.
  • Operates by damaging the membrane of the target cells, causing them to lose integrity and subsequently die.
• Mechanism:
  • A complement protein binds to the foreign agent. As it flows through the bloodstream, it accumulates more proteins, leading to membrane damage and eventual cellular destruction.
• Primary role is to coordinate the immune response by signaling phagocytes and other immune cells to attack tagged pathogens.

Direct Killers in the Immune System

• Key cells: Phagocytes (macrophages and neutrophils) are essential for directly attacking and eliminating invaders.

Summary Remarks

• Understanding both types of immunity is vital for appreciating how the body defends itself against diseases.
• Recognizing the roles of specific cells and systems within the immune system can help understand broader health implications.