Which substance released by T cytotoxic cells induces apoptosis in target cells?

Which substance released by T cytotoxic cells induces apoptosis in target cells?

• A. Perforin
• B. Granzymes
• C. Granulysin
• D. Lymphotoxin

Answer: (B)

T cytotoxic cells play a critical role in the immune response by identifying and eliminating infected or cancerous cells. One of the key mechanisms by which these cells induce apoptosis, or programmed cell death, in target cells is through the release of granzymes. Granzymes are serine proteases that, once delivered into the target cell, initiate a cascade of events leading to apoptosis.

When a T cytotoxic cell binds to an infected or malignant cell through specific receptors, it releases both perforin and granzymes. Perforin creates pores in the membrane of the target cell, allowing granzymes to enter. Once inside, granzymes activate various intracellular pathways that culminate in the activation of caspases, which are the enzymes responsible for carrying out the cell death program. This targeted approach to eliminating harmful cells is crucial for maintaining the body’s defense against pathogens and tumor cells.

While perforin is essential for delivering granzymes into the target cells and lymphotoxin plays a role in affecting cell function and survival, it is the granzymes specifically that directly trigger the apoptotic mechanisms within the cells. Understanding this distinction highlights the crucial role of granzymes in the function of T cytotoxic cells within the immune system.