Fig. 3.

Y. pseudotuberculosis yopH mutant strains coated with purified YopH block the immediate-early Ca²⁺ response in human neutrophils. (A) Real-time monitoring of intracellular Ca²⁺ in neutrophils infected with YopH-coated Y. pseudotuberculosis strains: yopH deletion mutant (ΔyopH + YopH), plasmid-cured mutant (YPIII + YopH), multiple yop mutant (MYM + YopH), and an isogenic multiple yop mutant deleted for yopB and yopD (MYMΔBD + YopH). The mean numbers (± SEM) of Ca²⁺ peaks (300–600 nM) generated within 10 min of infection in nine independent experiments were as follows for the various bacteria strains: ΔyopH + YopH, 0.38 ± 0.21; YPIII + YopH, 3.21 ± 0.58; MYM + YopH, 0.40 ± 0.18; MYMΔBD + YopH, 3.24 ± 0.74. (B) Coating of externally added purified YopH on different Y. pseudotuberculosis strains presented as number of molecules per cell (mean ± SEM of four independent experiments). (C) Western blot analysis of YopH in chloramphenicol-treated wild-type Y. pseudotuberculosis (WT) and YopH-coated yopH mutant (ΔyopH + YopH). YopD is shown as a loading control.