Normal Values for High Affinity Fc Gamma Receptor I (CD64) From Neonate to Young Adults

Abstract 4685

The high affinity Fc gamma receptor I (Fc gamma RI, cluster of differentiation 64 [CD64]) is normally expressed to a very low extent by neutrophils; during bacterial infections, the expression has been shown to increase in adults and newborn infants. However, the normal range in steady status remains unknown. To ultimately develop the novel measurement technique and clinical application of CD64 expression as an early diagnostic marker for bacterial infection, normal CD64 expression levels were determined in normal neonates, infants, young children, and adults who had no symptoms of infection, stable temperature, normal leukocyte counts and normal C-reactive protein levels, and who were not using steroids, immunosuppressive drugs, aspirin, or other non-steroid anti-inflammatory drugs in this study. To quantify the expression levels of neutrophil CD64, mean fluorescence intensity (MFI) on neutrophils was measured by flow cytometry in 420 samples. Subjects were assigned to 7 groups by age: neonates (group A, n = 76); 1 – 11 months (group B, n = 51); 1 – 5 years (group C, n = 87); 6 – 10 years (group D, n = 76); 11 – 15 years (group E, n = 77); 16 – 20 years (group F, n = 33); and over 21 years (group G, n = 20). Each expression level in groups A, B, and C was significantly higher than that in group G (P < 0.01); no differences were found among groups D, E, F, and G. These results suggest that normal cutoff levels of CD64 should be determined according to age to apply to the clinical setting because CD64 expression has a tendency to increase according to age, especially over 21 years.