TNF and malaria: We hypothesized that bacterial co-infection might exacerbate the host inflammatory response during malaria, leading to a lethal “cytokine storm.” We observed that single C. rodentium infection had little impact on plasma cytokine levels, whereas single P. chabaudi infection increased plasma levels of tumor necrosis factor (TNF), IL-6, interferon-γ (IFN-γ), and IL-17 during the second week of infection (Figure 4).