Tumor necrosis factor-α production by peripheral blood mononuclear cells after in vitro Escherichia coli challenge in early- vs. mid-lactation dairy cows

In this research communications, we characterized the in vitro production curve of tumor necrosis factor-α (TNF-α) by peripheral blood mononuclear cells (PBMC) challenged with Escherichia coli obtained from multiparous dairy cows in early lactation (EL, 14 ± 4 days in milk) vs. mid-lactation (ML, 123 ± 31 days in milk). We also investigated the impact of the type of serum (autologous vs. bovine fetal) used in cell culture on the TNF-α response. Peripheral blood mononuclear cells were isolated from EL (n = 7) and ML (n = 9) dairy cows. When PBMC were cocultured in autologous serum and challenged with E. coli, the supernatant TNF-α concentration was higher in the EL group than in the ML group (least-squares means [LSM], was 0.29 ± 0.1 vs. 0.24 ± 0.1 ng/mL, P = 0.004). In contrast, when PBMC were cocultured with bovine fetal serum, the lactation stage was not associated with the supernatant TNF-α concentration (P = 0.63). Our findings indicate that both the lactation stage and the serum environment used in cocultures are associated with TNF-α production in PBMC.