Immune Response Notes

The Immune Response

Overview

The immune response is a complex system involving various cells and processes aimed at defending the body against foreign invaders, known as antigens.

Key Players

Macrophages

• These cells engulf invaders (antigens) through a process called phagocytosis.
• After engulfing an antigen, the macrophage displays or presents the antigen on its cell membrane. This is crucial for activating other immune cells.

Helper T Cells

• Recognize the antigen presented by macrophages.
• Upon recognition, Helper T cells are stimulated and activated.
• Helper T cells play a central role in activating other immune cells, specifically B cells and T cells.

B Cells

• Activated by Helper T cells.
• Divide and differentiate into:
  • Plasma cells: Produce antibodies.
  • Memory B cells: Responsible for the secondary immune response.

T Cells

• Activated by Helper T cells.
• Divide and differentiate into:
  • Killer (Cytotoxic) T cells: Destroy infected cells by causing them to burst (lysis).
  • Suppressor T cells: Shut down and stop the immune response when the infection is under control.
  • Memory T cells: Provide long-term immunity by "remembering" the antigen.

Function of Immune Cells

Plasma Cells

• Produce antibodies, which are specialized proteins that recognize and bind to specific antigens.

Killer (Cytotoxic) T Cells

• Destroy infected cells, preventing the pathogen from replicating.
• Induce cell lysis, causing infected cells to burst and die.

Suppressor T Cells

• Regulate the immune response to prevent excessive inflammation and damage to healthy tissues.
• Shut down the immune response once the antigen has been cleared.

Memory T Cells and Memory B Cells

• Provide immunological memory, allowing for a rapid and robust response upon subsequent exposure to the same antigen.

Antibody Production

• Plasma cells produce antibodies that bind to the antigen.

Secondary Immune Response

• If the same antigen re-enters the body, memory cells trigger a faster and more potent immune response.
• This is the basis of long-term immunity and the effectiveness of vaccines.