An antibody that binds a neutrophil membrane protein, ERp72, primes human neutrophils for enhanced oxidative metabolism in response to formyl-methionyl-leucyl-phenylalanine. Implications for ERp72 in the signal transduction pathway for neutrophil priming.

Human neutrophils are primed by cytokines for enhanced oxidative metabolism in response to chemotactic factors, but the signal transduction pathways for cytokine activation and priming are unknown. Neutrophil priming may play an important role in mechanisms of host defense and inflammatory responses associated with autoimmune diseases. A rabbit antibody was produced that reacted with human neutrophils and induced priming in response to the chemoattractant, FMLP. The protein responsible for neutrophil priming in response to binding antibody was identified in a neutrophil cDNA library by expression cloning. The cloned protein absorbed the neutrophil-priming activity from rabbit serum. Furthermore, antibody priming activity was recovered by elution from the cloned protein. The gene for the protein associated with neutrophil priming was sequenced and identified as the endoplasmic reticulum protein, ERp72, which contains three copies of the active site sequences of protein disulfide isomerase. The antibody that primed neutrophils was shown to bind ERp72 in neutrophil membranes by immunoprecipitation of the same 72-kDa protein from neutrophils as a known antibody to ERp72. These studies implicate ERp72 in the signal transduction pathway for priming human neutrophils.