Answer: The cytokine that downregulates the immune response is IL-10 (Option D).
Step-by-step explanation:
A. TNF-α: Tumor Necrosis Factor-alpha (TNF-α) is a pro-inflammatory cytokine that is involved in initiating and promoting the immune response. It is not responsible for downregulating the immune response.
B. IL-5: Interleukin-5 (IL-5) is primarily involved in the growth, differentiation, and activation of eosinophils, a type of white blood cell involved in allergic and immune responses. It does not have a significant role in downregulating the immune response.
C. IL-1: Interleukin-1 (IL-1) is a pro-inflammatory cytokine that is involved in the activation of immune cells and the promotion of inflammation. It does not have a major role in downregulating the immune response.
D. IL-10: Interleukin-10 (IL-10) is an anti-inflammatory cytokine that plays a key role in downregulating the immune response. It inhibits the production of pro-inflammatory cytokines and reduces the activation of immune cells, helping to dampen the immune response and prevent excessive inflammation.
In summary, among the given options, IL-10 is the cytokine that downregulates the immune response. It acts as an anti-inflammatory cytokine, inhibiting pro-inflammatory cytokines and reducing immune cell activation.