Final answer:
Chemical messengers called cytokines and chemokines signal cell neighbors to initiate phagocytosis of dying cells.
Step-by-step explanation:
The initiation of phagocytosis of dying cells by cell neighbors is often signaled by the presence of chemical messengers called cytokines and chemokines. Cytokines are signaling molecules that allow cells to communicate with each other over short distances, while chemokines attract cells from longer distances through a process called chemotaxis. These chemical signals help coordinate the immune response and trigger phagocytic cells to engulf and destroy dying cells.