TNF and infection: Furthermore, a co-infection study on porcine bone marrow-derived dendritic cells (BMDC) experimentally infected with porcine reproductive and respiratory syndrome virus (PRRSV) and a secondary infection with S. suis showed that phagocytosis of bacteria was impaired when IL-6 and TNF-α were upregulated [44], pointing to a detrimental effect of IL-6 or TNF-α upregulation.