Which type of lymphocyte is involved in the direct killing of infected cells?

Which type of lymphocyte is involved in the direct killing of infected cells?

• A. Helper T-lymphocyte
• B. Memory B-lymphocyte
• C. Cytotoxic T-lymphocyte
• D. Natural killer cell

Answer: (C)

Cytotoxic T-lymphocytes are specialized immune cells that play a crucial role in the body's defense against infections, particularly those caused by viruses and some bacteria. They are adept at recognizing and directly killing infected cells, which is an essential function in controlling and clearing infections. When a cell becomes infected, it often presents infection-related antigens on its surface bound to major histocompatibility complex (MHC) molecules. Cytotoxic T-lymphocytes have specific receptors that can recognize these MHC-antigen complexes. Upon binding, these lymphocytes are activated, triggering a cascade of events that leads to the release of cytotoxic granules. These granules contain perforin and granzymes; perforin forms pores in the membrane of the infected cell, while granzymes enter through these pores and induce apoptosis (programmed cell death). This allows for the targeted elimination of cells that harbor pathogens, thus limiting the spread of the infection. The other types of lymphocytes mentioned serve different functions. Helper T-lymphocytes assist in orchestrating the immune response by activating other immune cells but do not directly kill infected cells. Memory B-lymphocytes are responsible for long-term immunity but do not participate directly in the killing of infected cells

Cytotoxic T-lymphocytes are specialized immune cells that play a crucial role in the body's defense against infections, particularly those caused by viruses and some bacteria. They are adept at recognizing and directly killing infected cells, which is an essential function in controlling and clearing infections.

When a cell becomes infected, it often presents infection-related antigens on its surface bound to major histocompatibility complex (MHC) molecules. Cytotoxic T-lymphocytes have specific receptors that can recognize these MHC-antigen complexes. Upon binding, these lymphocytes are activated, triggering a cascade of events that leads to the release of cytotoxic granules. These granules contain perforin and granzymes; perforin forms pores in the membrane of the infected cell, while granzymes enter through these pores and induce apoptosis (programmed cell death). This allows for the targeted elimination of cells that harbor pathogens, thus limiting the spread of the infection.

The other types of lymphocytes mentioned serve different functions. Helper T-lymphocytes assist in orchestrating the immune response by activating other immune cells but do not directly kill infected cells. Memory B-lymphocytes are responsible for long-term immunity but do not participate directly in the killing of infected cells