Acquired Immunity

Overview

• Acquired immunity includes:
  • Humoral immunity
  • Cell-mediated immunity
• Aim to simplify complex textbook explanations.

Humoral Immunity

• Steps Involved:
  1. Antigen Binding: An antigen binds to an antibody on a B cell.
  2. Engulfment: The B cell engulfs the antigen, presenting it on the surface via MHC-2 proteins.
  3. Helper T Cell Interaction: Helper T cell binds to the complex, releasing cytokines (chemical messengers).
  4. B Cell Activation: Cytokines induce B cell to divide into plasma and memory cells.
     • Plasma Cells: Produce and release antibodies against the specific antigen.
     • Memory Cells: Sensitized for rapid response upon re-exposure to the antigen.
  5. Antibody Binding: Antibodies bind to the antigen, triggering neutralization and destruction.

Cellular Immunity

• Activation Process:
  1. Naive T Cell Contact: Contacts the MHC-antigen complex, becoming activated.
  2. Cytokine Release: Activated T cell releases cytokines, promoting T cell proliferation.
• T Cell Types:
  • Helper/Inducer T Cells (CD4+):
    • Recognize self vs. non-self.
    • Release cytokines to recruit more white blood cells.
  • Regulatory T Cells:
    • Prevent immune overreaction.
    • Suppress immune response via cytokines.
  • Cytotoxic T Cells (CD8+):
    • Destroy infected, cancerous, or damaged cells.

Types of Immunity

Active Immunity

• Active Natural Immunity: Antibodies produced in response to live pathogen exposure.
• Active Artificial Immunity: Antibodies produced in response to vaccine exposure.

Passive Immunity

• Passive Natural Immunity:
  • Antibodies transferred from mother to baby (placenta or breast milk).
• Passive Artificial Immunity:
  • Immunoglobulins administered to provide antibodies.
  • No memory cell formation; helps current infection.

Next Steps

• Upcoming discussion on immune system malfunction and infection.