Reduced expression of C5a receptors on neutrophils from cord blood

Aim-To describe further functional deficiencies of neonatal neutrophils by measuring the expression of C5a receptors. Methods-C5a uptake was measured using flow cytometry with fluorescein isothiocynate labelled recombinant C5a. The response of neutrophils to stimulation with C5a and fMLP was tested by measuring migration and exocytosis of myeloperoxidase and lactoferrin. Results-C5a mean fluorescence on neutrophils from neonates was significantly lower (22.4 (SD 3.5)) than in adult controls (31.5 (3.1)). Neutrophils from neonates migrated poorly towards both C5a and fMLP compared with those from adult controls. Exocytosis of myeloperoxidase, but not lactoferrin from neonatal neutrophils stimulated with C5a, was significantly lower than in adult controls. fMLP stimulation, on the other hand, resulted in significantly higher exocytosis in neonates. Conclusion-The lower expression of C5a receptors on neutrophils from neonates could be related to reduced C5a mediated exocytosis of myeloperoxidase.