Final answer:
Leukocyte development is regulated by cytokines known as interleukins, which are signaling molecules critical for hemopoiesis and also play roles in immunity and inflammation.
Step-by-step explanation:
The development of the different subtypes of leukocytes is regulated by signaling molecules called cytokines, specifically interleukins.
Interleukins are a type of cytokine crucial for the process known as hemopoiesis, which is the formation of blood cellular components. These molecules were originally thought to be exclusively produced by white blood cells for communication among themselves. However, it is now understood that interleukins are secreted by various types of cells, including those in bone marrow and the endothelium. Interleukins not only regulate the differentiation and proliferation of leukocytes but are also involved in immunity and inflammation responses. With over a dozen identified, these molecules are typically named in a numbered sequence (e.g., IL-1, IL-2, IL-3).