Lecture Notes: T Lymphocytes

Overview

• T lymphocytes are formed in the bone marrow but mature in the thymus.
• Two main types: T Helper Lymphocytes and T Killer Lymphocytes.
• Both types have receptors complementary to antigens, similar to B lymphocytes.

T Killer Lymphocytes

• Misconception: They do not kill pathogens directly.
• Actual Function: Kill our own body cells that are infected or cancerous.

Process of T Killer Lymphocytes

1. Mutation and Infection:
   • Mutated cells can become cancerous.
   • Infected cells produce more pathogens.
2. Role of T Killer Cells:
   • Patrol tissues for infected or cancerous cells.
   • Destroy these cells to prevent damage to surrounding tissues.

Mechanism

• Antigen Presentation:

  • Infected cells present antigens on their surface.
  • This signals T Killer cells to target them.

• Clonal Selection and Expansion:

  • T Killer cells with complementary receptors undergo clonal selection.
  • They then undergo clonal expansion, forming:
    • Activated T Killer Cells
    • Memory T Killer Cells

Functions of Activated T Killer Cells

• Bind to infected cells.
• Release cytotoxic chemicals to kill infected cells.
• Prevent pathogen spread by destroying pathogens within cells.
• Induced cell death is followed by apoptosis; phagocytes clean up.

Role of Memory T Killer Cells

• Provide faster immune response in future infections.
• Help quickly eradicate infected cells upon re-exposure to the pathogen.

Important Concepts

• Clonal Selection: T Killer cells recognize and bind to specific antigens.
• Clonal Expansion: Proliferation of specific T Killer cells after recognition.
• Apoptosis: Programmed cell death of infected cells, aiding in cleanup.

Note: Understanding the distinct roles and mechanisms of T Killer and T Helper lymphocytes is crucial for comprehending immune responses and their regulation. Memory cells play a critical role in adaptive immunity by ensuring quicker responses upon re-infection.