Inhibition of the Fc receptor-mediated oxidative burst in macrophages by the Yersinia pseudotuberculosis tyrosine phosphatase.

Suppression of host-cell-mediated immunity is a hallmark feature of Yersinia pseudotuberculosis infection. To better understand this process, the interaction of Y. pseudotuberculosis with macrophages and the effect of the virulence plasmid-encoded Yersinia tyrosine phosphatase (YopH) on the oxidative burst was analyzed in a chemiluminescence assay. An oxidative burst was generated upon infection of macrophages with a plasmid-cured strain of Y. pseudotuberculosis opsonized with immunoglobulin G antibody. Infection with plasmid-containing Y. pseudotuberculosis inhibited the oxidative burst triggered by secondary infection with opsonized bacteria. The tyrosine phosphatase activity of YopH was necessary for this inhibition. These results indicate that YopH inhibits Fc receptor-mediated signal transduction in macrophages in a global fashion. In addition, bacterial protein synthesis was not required for macrophage inhibition, suggesting that YopH export and translocation are controlled at the posttranslational level.