Final answer:
Interleukin-10 released by helper T cells primarily functions to limit inflammation by acting on various immune cells, including macrophages, suppressing their inflammatory response. Therefore, the correct answer to the student's question is D) macrophages.
Step-by-step explanation:
The interleukin-10 (IL-10) cytokine, which is released by helper T cells, primarily functions to limit inflammation and the immune response. The IL-10 cytokine does so by acting on various cells, including T cells, B cells, macrophages, and dendritic cells. Its effect on these cells is generally immunosuppressive, as it helps to prevent damage to the host's tissues by down-regulating the expression of pro-inflammatory cytokines, MHC class II antigens, and co-stimulatory molecules on macrophages and dendritic cells. In the context of the question, it is known that interleukin-10 can affect macrophages by inhibiting their function and cytokine production, ultimately leading to decreased inflammation.
Therefore, the answer to the student's question is D) macrophages, as these are the types of cells that can be activated by the release of interleukin-10 from the helper T cells. Macrophages are capable of both phagocytizing pathogens and producing chemicals that promote inflammation; however, under the influence of IL-10, their inflammatory response is mitigated.