Step 1: Recall the functions of major cytokines.
\[
\begin{aligned}
\mathrm{IL\!-\!2} &\rightarrow \text{T-cell proliferation},
\mathrm{IFN\!-\!\gamma} &\rightarrow \text{Macrophage activation},
\mathrm{TNF\!-\!\alpha} &\rightarrow \text{Pro-inflammatory cytokine},
\mathrm{IL\!-\!10} &\rightarrow \text{Anti-inflammatory / Immunosuppressive}.
\end{aligned}
\]
Step 2: Identify the immunosuppressive cytokine.
IL-10 suppresses inflammatory cytokine production and limits excessive immune responses.
Hence,
\[
\boxed{\mathrm{IL\!-\!10}}
\]
is the correct answer.
Therefore,
\[
\boxed{(C)}
\]
is the correct answer.