Polymorphonuclear neutrophils (PMN) represent the most abundant circulating immune cells and act as the first leukocytes which rapidly migrate to the site of infection for phagocytosis and killing of invading microorganisms.Dysfunction of neutrophils has been linked to diverse inflammatory diseases in humans and in mastitis in dairy cows.Recently ,both NOD1 and NOD2 have been identified in bovine neutrophils by our group, and we found a significant down-regulation of NOD1, but not NOD2 protein, in the neutrophils of periparturient dairy cows that are known to be susceptible to increased incidence and severity of infectious diseases such as mastitis and metritis, However, it remains to be elucidated whether NOD1 is required for effective neutrophil immune responses to bacterial infection.The present study was conducted to investigate the effect of intracellular receptor NOD1 on the functionality of PMN in dairy cows.PMN was isolated from peripheral blood of clinically healthy heifers.The cells were pre-incubated with NOD1 selective inhibitor ML130 for 2 h, and then exposed to 100 ng/ml lipopolysaccharide (LPS) for further 4 h.Expression of NOD1 protein was determined by Western blot and the mRNA of proinflammatory cytokines (TNF-α, IL-1β and IL-8), chemotaxis cytokine CXCL2 and adherence molecular (CD11b/CD18 and CD62L) evaluated by qPCR.Annexin V/PI staining was employed to detect cell apoptosis.The capacity of phagocytosis and oxidative burst was evaluated by flow cytometry and cell migration evaluated using Transwell chamber.Upon LPS stimulation, inhibition of NOD1 by ML130 significantly inhibited the expression of NOD1 protein and down-regulated the mRNA of TNF-α, IL-1β, IL-8, CXCL2 and CD62L.However, the CD11b/CD18 mRNA expression was not affected by NOD1 inhibition.Inhibition of NOD1 also diminished the phagocytosis and oxidative burst as well as migratory capacity of PMN and increased the number of apoptotic cells in response to LPS stimulation.These data suggest that the immune function of PMN in dairy cows is NOD1-dependent.