CCL2 and Flavivirus Infections: These observed differences between HFF-1 and U937-DC-SIGN cells could be associated with the differences in the induced innate immune response of each cell type to Flavivirus infection; it has been reported that DENV-infected monocytes secrete MCP-1, interferon γ-induced protein (IP)-10, IL-6, IL-8, IL-10, and IL-1β.