Fc and complement receptor (CR1 and CR3) expression on neonatal human polymorphonuclear leukocytes

Fc gamma receptor III (Fc gamma RIII) and complement receptors (CR1 and CR3) were examined on polymorphonuclear leukocytes (PMN) from neonatal cord blood and adult blood using monoclonal antibodies directed against these receptors. Receptor expression was determined by flow cytometry. Fc gamma RIII, CR1 and CR3 expression was examined in whole blood at 4 degrees C, at 37 degrees C with or without stimulation with the chemotactic peptide f-met-leu-phe, and on PMN isolated by Ficoll-Hypaque centrifugation and dextran sedimentation. There was no significant difference between adult and cord PMN in the percent of cells which expressed Fc gamma RIII, CR1 and CR3 when examined in whole blood at 4 or 37 degrees C, or following stimulation with f-met-leu-phe. The percentage of PMN expressing CR1 and CR3 was lower on cord PMN compared to adult PMN when these cells were examined following Ficoll-Hypaque centrifugation and dextran sedimentation. The mean peak fluorescence of PMN which stained positively for CR1 and CR3 increased following f-met-leu-phe treatment of whole blood from adults and neonates. Since neonatal cord PMN were capable of upregulating complement receptors in response to chemotactic factors these results do not explain the increased susceptibility to infection exhibited by neonates.