TNF and infection: For instance, we have shown that subcutaneous injection of live Escherichia coli upregulated mRNA levels of interleukin 1 beta (IL-1β), tumor necrosis factor-alpha (TNF-α), interleukin 6 (IL-6), and cyclooxygenase-2 (COX-2) in the hippocampus and hypothalamus of mice, and induced sickness behavior within 4 h of infection [1].