Which of the following is not considered a type of cytokine?

Cytokines are a diverse group of small proteins that are crucial in cell signaling in the immune system. They play roles in various immune responses, inflammation, and cell communication. The types mentioned in the question, including interferons, interleukins, and monokines, are all well-known cytokines that perform specific functions within the immune response.

Interferons are a class of cytokines that are particularly important in the antiviral response and activate immune cells. Interleukins are a group of cytokines that are mainly produced by leukocytes and are involved in the communication between immune cells. Monokines are a type of cytokine released from monocytes and macrophages, mediating various immune functions.

Since all of the options listed are recognized types of cytokines, selecting that "all of these are types of cytokines" accurately reflects the knowledge that each mentioned category plays a role in the immune system as cytokines. Therefore, this choice is correct, as it confirms the classification of the provided types as part of the broader category of cytokines.