FIG. 2.

Binding of fluorescein N-formyl hexapeptides to their receptors on granulocytes preincubated with various strains of preopsonized Y. enterocolitica. Granulocytes were preincubated with medium only, pVY⁻ or pYV⁺ Y. enterocolitica, or Y. enterocolitica W22703(pGC1152) YadA⁺ YopH⁻ for 30 min. After removal of nonadherent bacteria, the pellet was incubated with N-formyl-Nle-Leu-Phe-Nle-Tyr-Lys-FITC at 4°C and analyzed by flow cytometry (gray bars). The specificity of the binding of this fluorescein hexapeptide to granulocytes was determined by measuring the residual binding of N-formyl-Nle-Leu-Phe-Nle-Tyr-Lys-FITC after preincubation of the granulocytes with 10 μM f-MLP for 5 min at 4°C (black bars). Values for controls are represented by the open bars. Results are expressed as the means of the values determined for fluorescence intensity. Data are representative of results from two independent experiments. A.U., arbitrary units.