Unit D

Module 8 ~ Lesson 1

The Second Line of Defence

As effective as the physical and chemical barriers of the body are, there may occasionally be a breach in the defence system. When pathogens are provided access to people's internal systems by breaches such as cuts or scrapes, the second line of defence is called into action. Macrophages and other phagocytotic cells surround and engulf the invading pathogens. This is a non-specific defence, or cell-mediated immunity, which includes neutrophils, monocytes, and T-cells. 

The T-cells involved in the cell-mediated (non-specific) immune response are specialized to perform a number of functions. Helper, killer, suppressor, and memory T-cells all play specific roles. They not only defeat pathogens but also ensure that the body is protected from further infections. By ridding the body of pathogens, the lymphatic system and immunity help to maintain homeostasis.


Watch the video below. The explanation is more detailed than is required for this course, but the animations are clear and may help you visualize the process.