Clinical Value Of CD64 Surface Expression On Neutrophils In Children With Rheumatic Diseases

Background Common bacterial and opportunistic infections are a major cause of mortality in patients who are immunosupressed owing to treatment with corticosteroids or cytotoxic drugs. Common laboratory tests for infection lack sensitivity and specificity. The Fc receptors on white blood cells are very important for effective phagocytosis of bacteria. One of the Fc receptors for IgG is FcYR I (CD64). It is up regulated on neutrophils within 4 to 6 hours after stimulation with interferon y, granulocyte colony stimulating factor or lipopolysaccharide as a physiological response to microbial wall products and some cytokines.Objective To study the clinical value of CD64 surface expression on neutrophils in children with rheumatic diseases.Methods 95 children were studied including normal controls (n=30), bacterial infections (n=27), CTD&JIA (n=29, SOJIA excluded) and SOJIA (n=9). All patients in the later two groups were active rheumatic diseases with systemic infections excluded clinically. CD64 surface expression on neutrophils was measured quantitatively using QuantiBRITE flow cytometry technique. SPSS 10.0 for Windows was used to perform statistical analysis.Results The mean antigen-per-cell (APC) of CD64 on neutrophil surface in normal controls was 1428 + 528, without difference between two genders. The neutrophil CD64 level was 1654?32 in patients with CTD and JIA (SOJIA excluded), showing no significance when comparing to that of normal controls (p>0. 05). Compared with normal controls and patients with CTDJIA (SOJIA excluded), the expression of CD64 was significantly upregulated in patients with bacterial infections and SOJIA (p<0. 001). In all patients with JIA, CD64 was higher in children with SOJIA than those with other subtypes of JIA (p<0.001), while the major indicators for inflammation such as WBC, Neu, ESR and CRP remained no difference (p>0. 05).Conclusion These results indicate that quantitative measurement of neutrophil CD64 can distinguish between bacterial infection and the flare of autoimmune rheumatic diseases such as SLE, JDM, and some subtype of JIA (with the exception of SOJIA). CD64 can also help rheumatolegists distinguish between SOJIA and other subtypes of JIA who has fulfilled the definition of JIA.