Paraformaldehyde fixation prior to mAb staining enhances binding of certain epitope-specific mAbs to CCR5 on BCD-treated cells.

(A) BCD-treated CEM-R5 cells were fixed with paraformaldehyde immediately after treatment and then examined with the indicated antibodies using flow cytometric analysis. The results for untreated cells are expressed in a filled area peak and the BCD-treated cells are graphed using a solid line. (B) Untreated, 10 mM BCD-treated, or 0.1% Triton X-100 permeabilized cells were stained with anti-CCR5 (45531) and PI as described in “Materials and methods.” CCR5 staining is shown in green, nuclear PI staining is shown in red, and the blue outlines are phase-contrast overlays. Bright yellows or bright reds indicate permeabilized cells. The bottom picture shows a wider view of the cell population for each treatment. Magnification, × 630.