<i>B. cenocepacia-</i>induced macrophage IL-1β secretion through cooperation between the T6SS and the T2SS.

<p>Graphs represent mean ± SEM from three independent experiments. A. Macrophages were infected with <i>B. cenocepacia</i>-MH1K, Δ<i>T2SS</i>, Δ<i>T3SS</i>, <i>T4SS-1</i>, Δ<i>fliCD</i>, Δ<i>T3SS-</i>Δ<i>fliCD</i>, <i>T6SS</i>+ or Δ<i>T6SS</i> at an MOI of 50 for 1 h and extracellular bacteria removed with gentamicin. ELISA was used to quantify IL-1β in cell supernatants at 24 h post-infection. ***, <i>p</i>≤0.001 compared to macrophages infected with MH1K. B. Macrophages were infected as in (A). At 1 h post-infection, the cells were lysed and CFUs were determined. The Invasion Index was calculated relative to MH1K. ***, <i>p</i>≤0.001 values compared to macrophages infected with MH1K; NS, non significant. C. Macrophages were infected as in (A) with <i>B. cenocepacia</i> MH1K, <i>T6SS</i>+, <i>T6SS</i>+-Δ<i>T2SS</i>, Δ<i>T6SS</i>, Δ<i>T6SS-</i>Δ<i>T2SS</i>, <i>T6SS</i>+-Δ<i>zmpA</i>, <i>T6SS</i>+-Δ<i>zmpB</i> or <i>T6SS</i>+-Δ<i>zmpAB</i>. ELISA was used to quantify IL-1β in cell supernatants at 24 h post-infection. ***, <i>p</i>≤0.001 values compared to macrophages infected with T6SS+. D. Macrophages were infected with the same bacterial strains as in (C). Supernatants of infected macrophages were used to quantify the total LDH activity at 24 h post-infection. *, <i>p</i>≤0.05 values compared to macrophages infected with MH1K; NS, non significant. E. Macrophages were infected with <i>T6SS+</i>, <i>T6SS+-</i>Δ<i>T2SS</i> and Δ<i>T6SS-</i>Δ<i>T2SS</i> at different MOI for 1 h and then treated with gentamicin to remove extracellular bacteria. ELISA was used to quantify IL-1β in cell supernatants at 24 h post-infection. *, <i>p</i>≤0.05; **, <i>p</i>≤0.01 and ***, <i>p</i>≤0.001 values compared to macrophages infected with <i>B. cenocepacia</i> mutants at an MOI of 10. NS, non significant.