Increased numbers of CD64⁺ PMNs in the blood of sickle cell patients in crisis. Scattergram showing flow cytometric analysis of the distribution of CD64⁺ PMNs in the blood of 16 patients in crisis (•), 11 patients out of crisis (○), and 22 normal healthy subjects (▵). The horizontal line (26%) represents a threefold value above the median percentage CD64⁺ PMNs of the 22 normal subjects. The figure shows that, whereas CD64⁺ PMNs both in and out of crisis were supranormal (in crisis, χ² = 23.4, P < .001; out of crisis, χ² = 5.8, P = .02), their proportion in crisis was significantly greater than that out of crisis (χ² = 5.53, P = .025). PMNs (1 × 10⁶ cells) were incubated with anti-CD64 antibody (10 μL) for 30 minutes at 4°C. Cells were washed and the FITC conjugated Ig (25 μL) was added for a further 30 minutes at 4°C. Cells were then washed twice, fixed with 1% paraformaldehyde-PBS, and analyzed using flow cytometry.