Final answer:
The statement is true; cytokines do affect neighboring cells in their vicinity, providing vital communication between immune cells and other cell types to mediate immune responses.
Step-by-step explanation:
The statement that cytokines affect cells near the cells that secreted them is true. Cytokines are signaling molecules playing a crucial role in cellular communication. They are secreted by a range of cells, including immune cells like leukocytes and macrophages, and they act locally as autocrine or paracrine factors. This action facilitates both early induced responses and later during adaptive immune responses. For instance, interferons, a class of cytokines, are released by virus-infected cells and warn nearby cells to produce compounds that inhibit viral replication. Similarly, cytokines can induce neighboring uninfected cells to enter a state that enhances their immune response.