Activation of monocytes and neutrophils is accompanied by expression of a unique CD18 epitope recognized by mAb MEM-148.

(A) PBLs were left either untreated or treated with PMA or HA-Ig for 2 hours, stained by MEM-148, and analyzed by flow cytometry. As controls, an irrelevant IgG1 mAb (Control) and a standard CD18 mAb MEM-48 (CD18) were used. The results are expressed as standard side scatter (y-axis) versus logarithmic fluorescence intensity (x-axis) contour plots. The gates corresponding to neutrophils (N), monocytes (M), and lymphocytes (L) are shown in the first plot (top, left). The bottom panel shows staining of untreated neutrophils isolated from urine of a patient following prostatectomy. (B) Purified monocytes and neutrophils were activated with PMA and at different time points stained with MEM-148 or standard CD18 mAb (MEM-48). Results from 3 experiments are represented as mean fluorescence intensity (MFI) ± SD values (arbitrary units) calculated from geometric means of fluorescence intensity after subtraction of irrelevant isotype control.