TNF and mastitis: Akhtar et al. found that the protein and mRNA levels of proinflammatory cytokines (IL-6, IL-1β and TNF-α) in infected tissues were increased compared with those in uninfected tissues and that activation of the NF-κB/MAPK signaling pathway through TLRs further triggered mastitis-related gene expression, followed by activation of the innate immune response [44].