QUANTITATION OF SURFACE CD14 ON HUMAN MONOCYTES AND NEUTROPHILS

The absolute number of membrane-expressed CD14, the most important end otoxin receptor, on human monocytes and neutrophils shows remarkable v ariation in the literature, To quantify these numbers two fluorescence methods using fluorescein isothiocyanate (FITC)-labeled monoclonal an tibodies (mAb) were applied, A commercially available set of standard beads was used in flow cytometry to quantitate CD14 with eight differe nt mAbs, Independent from their isotype the various mAbs showed minor differences and indicated that peripheral blood monocytes expressed 99 ,500-134,600 015,400 +/- 10,600) and neutrophils 1,900-4,400 (3,300 +/ - 800) CD14 receptors, There was no significant difference in CD14 exp ression on leukocytes in unprocessed freshly obtained whole blood and after a Ficoll isolation procedure, However, a short temperature shift resulted in a 1.3- to 1.6-fold up-regulation of CD14. The results obt ained with the reference beads were verified with fluorescence Scatcha rd analysis and spectrofluorometry using mAb 26ic-FITC and showed 109, 500 CD14 per monocyte and 6,700 CD14 per neutrophil, For comparison th e number of CD14 on the monocytic THP-1 cells and Fc gamma-receptors o n human leukocytes were determined using the reference beads and now c ytometry and gave results comparable to published data, Our data indic ate that resting human monocytes express roughly 110,000 CD14 molecule s on their surface using a simple fluorometric assay, Correct determin ation of the number of CD14 and other cell surface receptors is of imp ortance in the monitoring of septic patients.