Question 18

Cytokines are released by one type of immune cell to activate another type of immune cell.

Cytokines serve as crucial signaling molecules in the immune system, facilitating communication between different immune cells and activating them to respond effectively to pathogens.

A) Cytokines

Cytokines are indeed the chemicals released by certain immune cells, such as T-helper cells, to activate other immune cells, including B cells and cytotoxic T cells. This activation is essential for coordinating the immune response and ensuring that the immune system functions effectively against infections.

B) Granzymes

Granzymes are serine proteases released by cytotoxic T cells and natural killer cells, primarily to induce apoptosis in infected or malignant cells. They do not play a role in directly activating other immune cells, which makes this option incorrect in the context of the question.

C) Lysozymes

Lysozymes are enzymes that break down bacterial cell walls and are found in various bodily secretions, such as saliva and tears. While they contribute to the immune response, they do not function as signaling molecules to activate other immune cells, rendering this option incorrect.

D) Perforin

Perforin is a protein released by cytotoxic T cells that forms pores in the membranes of target cells, facilitating the entry of granzymes to induce cell death. Like granzymes, perforin does not activate other immune cells and is therefore not the correct answer in this context.

Conclusion

Cytokines are essential for the communication and activation of various immune cells, making them the correct answer to the question. In contrast, granzymes, lysozymes, and perforin serve different functions within the immune response that do not involve activating other immune cells, thus confirming their incorrectness in this scenario.