What type of immune cell is responsible for directly killing pathogens?

• A. Helper T cells
• B. B cells
• C. Cytotoxic T cells
• D. Memory T cells

Answer: (C)

Cytotoxic T cells are specialized immune cells primarily tasked with directly attacking and killing infected cells and cancerous cells. They recognize abnormal or infected cells by identifying specific antigens presented on their surface, often through Major Histocompatibility Complex (MHC) molecules. Once they bind to these targets, cytotoxic T cells release toxic molecules, such as perforin and granzymes, which create pores in the infected cell's membrane and induce cell death through apoptosis.

While helper T cells play a crucial role in coordinating the immune response and B cells are responsible for antibody production, they do not engage directly in killing pathogens. Memory T cells serve to provide long-term immunity by remembering past infections and quickly responding upon re-exposure to the same pathogen, but they also do not directly kill pathogens. Thus, cytotoxic T cells are the key players in the direct elimination of infected or malignant cells in the body.