Monitoring of neutrophil priming in whole blood by antibodies isolated from a synthetic phage antibody library

Neutrophil activation is a multistep process. In vitro activation of neutrophils with semiphysiological activators is optimal only after preactivation or priming with cytokines, chemotaxins, and/or bacterial products. Until now, no antibodies have been developed that can distinguish between resting and (cytokine) primed neutrophils with a sufficient dynamic range necessary for screening clinical samples. We have isolated two human phage antibodies, designated MoPhab A17 and A27, from a synthetic bacteriophage antibody library. These phage antibodies recognize epitopes that are upregulated on neutrophils present in whole blood treated with low priming concentrations of cytokines, such as GM‐CSF and TNF‐α. This induction was time‐ and concentration‐dependent and optimal at concentrations that are sufficient for priming functional responses in neutrophils: GM‐CSF (10 pM) and TNF‐α (100 IU/ml). PMNs, isolated from the peripheral blood of chronic obstructive pulmonary disease (COPD) patients with a clinical exacerbation, exhibited a partial in vivo primed phenotype. These antibodies promise to be an ideal tool to monitor disease activity in whole blood of patients with inflammatory diseases.