doi:10.1006/cyto.2001.0880, available online at http://www.idealibrary.com on SHORT COMMUNICATION DIFFERENCES IN THE EXPRESSION OF CD64 AND mCD14 ON POLYMORPHONUCLEAR CELLS AND ON MONOCYTES IN PATIENTS WITH SEPTIC SHOCK Eberhard Barth, 1 Guenther Fischer, 1 Elisabeth Marion Schneider, 2 Jochen Wollmeyer, 1 Michael Georgieff, 1 Manfred Weiss 1 The present study was performed to clarify the time course of the expression of CD64, the Fc gamma receptor type I (FcR1), and membrane-bound CD14 (mCD14), one of the major receptors for endotoxin, on polymorphonuclear leukocytes (PMN) and monocytes in 22 postoperative/post-traumatic patients with septic shock. Therefore, the expression of CD64 and mCD14, and serum concentrations of granulocyte colony-stimulating factor (G-CSF) and interferon- (IFN-) were determined by flow cytometric analysis and enzyme-linked immuno- sorbent assay (ELISA), respectively, from the first day of septic shock onwards over a period of 14 days. When compared to the values of 12 healthy controls, CD64 expression was elevated significantly on PMN and monocytes of the patients, whereas the expression of mCD14 was decreased significantly at all days. The initially increased expression of CD64 on PMN and monocytes decreased within the first days of septic shock. The already initially decreased mCD14 expression decreased further on PMN, but not on monocytes. Serum concentrations of G-CSF and IFN- during the study period were significantly higher than those of the control group. The differences in the kinetics of CD64 and mCD14 expression in patients with septic shock may be explained by different regulatory effects of cytokines, such as G-CSF and IFN-.  2001 Academic Press In peripheral blood of healthy people, CD64 (Fc gamma receptor type I, FcRI) is expressed constitu- tively on monocytes but infection-induced on polymor- phonuclear leukocytes (PMNs). 1 The expression of CD64 on mature PMN can be induced by cytokines such as interferon- (IFN-) and granulocyte colony- stimulating factor (G-CSF) (Table 1). Upregulation of CD64 in vivo has been shown to be associated with enhanced neutrophil function. 2 Thus, an increase in CD64 expression may indirectly indicate activation of PMN. Membrane-bound CD14 (mCD14) is an import- ant receptor for Gram-negative bacterial lipopoly- saccharide (LPS) and therefore relevant for effective endotoxin clearance, 3 and activation of monocytes and PMN. 4 mCD14 is expressed constitutively by mono- cytes, macrophages and PMN. 5 In patients, the time pattern of the expression of CD64 and mCD14 on monocytes and PMN during septic shock is unknown. Different patterns are expected, because the expression of CD64 and mCD14 differs in density, 6 occurs constitutively and/or is infection-induced, 1 and is differentially regu- lated by cytokines, such as G-CSF and IFN- (Table 1). Thus, the present study was performed to clarify the kinetics of CD64 and mCD14 expression on monocytes and neutrophils, and to find out whether there is an association between serum concentrations of G-CSF and IFN- and the expression of CD64 and mCD14 in patients during septic shock. From the Departments of 1 Anaesthesiology and 2 Experimental Anaesthesiology, 1Universitaetsklinikum, Steinhoevelstr. 9, 89075 Ulm, Germany Correspondence to: Eberhard Barth, M. D., Department of Anaes- thesiology, Universitaetsklinikum, Steinhoevelstr. 9, 89075 Ulm, Germany. E-mail: eberhard.barth@medizin.uni-ulm.de Received 12 October 2000; received in revised form 6 February 2001; accepted for publication 13 March 2001  2001 Academic Press 1043–4666/01/110299+04 $35.00/0 KEY WORDS: CD14/CD64/monocytes/PMN/sepsis Supported by: Institutional departmental fund CYTOKINE, Vol. 14, No. 5 (7 June), 2001: pp 299–302 299