Final answer:
The immune system uses cytotoxic T cells to destroy abnormal cells by releasing toxins, NK cells to trigger apoptosis, and oncolytic viruses to selectively infect and kill cancer cells without harming normal cells.
Step-by-step explanation:
Main Approaches to Destroy 'Abnormal' Host Cells
There are several mechanisms that the immune system uses to destroy virus-infected or cancerous cells. Here are three main approaches:
Cytotoxic T Cells (CTLs)
Cytotoxic T cells, also known as killer T cells, identify and destroy abnormal cells by recognizing non-self antigens presented on the surface of these cells. Once activated, they release toxins that form pores in the membrane of the infected or cancerous cells, which causes the cell to burst, destroying both the cell and any pathogens inside it.
Natural Killer (NK) Cells
Natural Killer (NK) cells are able to induce apoptosis, or programmed cell death, in infected or tumor cells. Following apoptosis, phagocytic cells digest the cell debris. NK cells constantly patrol the body, and their activity is crucial for controlling infections and preventing cancer progression.
Oncolytic Viruses
In addition to the body's natural defenses, oncolytic viruses are a therapeutic option that involves using viruses to infect and kill cancer cells. These viruses are designed to selectively target cancerous cells without harming normal cells, and they are currently being studied in clinical trials as potential cancer treatments.