Abstract: Abstract Objective: To study the clinical value of CD64 surface expression on neutrophils in children with connective tissue diseases(CTDs). Methods: 73 children were studied including normal controls (n=30), cases with bacterial infection (n=27) and CTDs (n=16). All patients in CTD group (11 cases of juvenile systemic lupus erythymatosus and 5 cases of juvenile dermatomyositis) were active rheumatic diseases with systemic infections excluded clinically. CD64 surface expression on neutrophils was measured quantitatively using QuantiBRITE flow cytometry technique. SAS System for Windows V8 was used to perform statistical analysis. Results: The mean antigen-per-cell of CD64 on neutrophil surface in normal controls was 1434±529, without difference between two genders（1300±494 vs 1556±547，p>0.05）. The neutrophil CD64 level was 1391±576 in patients with CTDs, showing no significance when comparing to that of normal controls (p>0.05). Compared with normal controls and patients with CTDs, the expression of CD64 increased significantly in patients with bacterial infection (4995±2636, p<0.0001). Conclusion: CD64 surface expression on neutrophils upregulates in patients with bacterial infection, however it does not elevate in active diseases of CTDs in children. It might become a potential indicator for distinguishing bacterial infection and the flare of connective tissue diseases.

Key words: CD64, connective tissue diseases, infection, bacterial, children