Understanding Acquired Immunity Mechanisms

Nov 1, 2024

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.