CD64 is a high-affinity FcγRI receptor expressed by activated neutrophils that has been recently evaluated as a potential sepsis parameter. In the present study, the kinetics of neutrophil membrane CD64 expression were examined during a standardized inflammatory response, using a human endotoxemia model, and compared with hematological indices, CRP, cytokines and interleukins. Ten healthy subjects received 2 ng/kg intravenous Escherichia coli lipopolysaccharide (LPS). After administration of LPS, neutrophil CD64 showed a biphasic response, characterized by a first increase from 108.5 ± 7.5 to 133 ± 6 AFU after 1 h ( P = 0.047) and a second increase that started at 6 h and reached its maximum of 167 ± 13 AFU at 22 h ( P < 0.0001). CRP concentrations increased to 40 ± 5 mg/dl 22 h after the administration of LPS. The cytokines and interleukins reached their maximum response within 1—2 h. The maximum values of pro-inflammatory cytokines (TNF-α, IFN-γ and IL-6) correlated with the CD64 expression at 22 h after LPS administration ( r2 = 0.76, r2 = 0.78, r2 = 0.81, respectively, all P < 0.05), whereas this correlation was not found for the anti-inflammatory IL-10 ( r2 = 0.058, P = 0.54), suggesting that neutrophil CD64 expression might be a quantitative marker for innate immunity that could easily be used in the clinical setting.
Pseudothrombocytopenia is usually associated with blood specimens anticoagulated with ethylenediamine tetraacetic acid (EDTA) or other anticoagulants. It may be caused by temperature-independent, EDTA-dependent antibodies of the immunoglobulin-M (IgM) type. Here a patient with EDTA-independent and temperature-independent pseudothrombocytopenia mediated by IgM or IgM-containing immune complex is reported, and a reliable method is described for a proper counting of platelets in such cases.
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