Figure 1.

Salmonella SPI-2 T3SS Effector SteD Reduces Surface Levels of Mature MHCII Molecules

(A) Mel Juso cells were infected with WT or mutant Salmonella strains for 16 hr and surface levels of mMHCII were measured by flow cytometry using mAb L243 (that specifically recognizes mature HLA-DR). The error bars represent SD of the geometric mean fluorescence of two independent experiments performed in duplicate.

(B) Representative FACS plots showing surface levels of mMHCII in infected cells (i) compared to uninfected cells (ui). The histograms show surface levels of mMHCII in infected (i, blue) and uninfected (ui, dark gray) cells. The cells labeled with isotype control antibody are shown in light gray.

(C) Mel Juso cells were infected with ΔsteD strain carrying pWSK29, expressing SteD-2HA regulated by its endogenous promoter (psteD). The infected and uninfected cells were discriminated using anti-Salmonella CSA-1 antibody after fixation. The data represent surface levels of mMHCII in infected cells as a percentage of those in uninfected cells from the same sample.

(D) Mel Juso cells were transfected with vectors encoding GFP-tagged effectors, and mMHCII was analyzed by flow cytometry. The data represent surface levels of mMHCII in transfected cells as a percentage of those in untransfected cells from the same sample.

(C and D) Error bars represent SD of the geometric mean fluorescence of three experiments done in duplicate and were analyzed through comparison with WT Salmonella (C) or GFP-only transfected cells (D) by one-way ANOVA followed by Dunnett’s multiple comparison test. ^∗∗∗p < 0.001, ^∗∗p < 0.01, ^∗p < 0.05, and not significant, ns.