Killer T-cells, also known as cytotoxic T-lymphocytes, are a type of white blood cell that play a crucial role in the immune system. They are responsible for identifying and destroying infected or cancerous cells in the body. By recognizing specific markers on these cells, killer T-cells can effectively target and eliminate threats. These cells are activated when they encounter an infected cell displaying foreign antigens. Once activated, killer T-cells release substances that induce cell death, helping to prevent the spread of infection. Their ability to remember past infections also allows for a quicker response during future encounters with the same pathogen.