Effect of RBC transfusion on plasma modulation of FMLP-triggered chemotaxis. Neutrophils were incubated in the upper compartment of a chemotaxis chamber in the absence (Nil) or presence of various dilutions of plasma obtained from 5 patients before (open bars) and after (black bars) RBC transfusion. The locomotory response of neutrophils to 10 nM FMLP in the lower compartment was tested after 45 minutes' incubation. Results are expressed as mean ± 1 SD of 3 experiments with neutrophils from different donors. Ctrl indicates control.