TNF and infection: Our results show that Brucella abortus 2308 infection in mice induced a significant increase in circulating levels of IL-6, IL-12, TNF-α, and IFN-γ; an increase in the number of macrophages and dendritic cells in the spleen; a decrease in hippocampal serotonin levels by day 14; and loss of physical strength, balance, and hopelessness, as previously reported by our group [18].