Section outline


  • Hi everyone!
    Today, we’ll explore the third line of defense, the most advanced part of your immune system. Unlike the first and second lines, this one is highly specific—it targets particular pathogens and can “remember” them. That’s why you usually only get diseases like chickenpox once!

    This system includes B cells, T cells, antibodies, and memory cells, all working together to destroy invaders and build long-term immunity. It’s also the reason vaccines are so effective. By understanding this defense, you’ll better grasp how we fight infections long-term and how modern medicine helps us strengthen it.


    13.1 Topic Learning Outcomes
    By the end of this lesson, you will be able to:
    13.1.1 Define the third line of defense.
    13.1.2 Differentiate between B cells and T cells.
    13.1.3 Explain how antibodies and memory cells contribute to immunity.


    13.2 List of Subtopics
    13.2.1 A    daptive immunity overview
    13.2.2 B cells and antibody production
    13.2.3 T cells and destruction of infected cells
    13.2.4 Memory cells and long-term immunity


    13.3 Lecture Video