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. 2020 Jun 3;11:1115. doi: 10.3389/fimmu.2020.01115

Figure 6.

Figure 6

Phagocytosis of live S. sonnei is required for the full activation of the NLRP3 inflammasome. (A) J774A.1 macrophages were primed with 1 μg/ml LPS for 4 h and then treated with cytochalasin D for 0.5 h. The cells were then infected with 50 MOI S. sonnei for an additional 20 h. The levels of IL-1β and TNF-α in the supernatants were measured by ELISA. (B) The TLR2 mRNA expression of mock or TLR2 knockdown J774A.1 macrophages was measured by RT-qPCR. Mock or TLR2 knockdown J774A.1 macrophages were stimulated with 1 μg/ml Pam3CSK4 for 6 h. The levels of TNF-α in the supernatants were measured by ELISA. (C) Mock or TLR2 knockdown J774A.1 macrophages were primed with 1 μg/ml LPS for 4 h and then infected with 50 MOI live, heat-killed or freeze/thaw-killed S. sonnei for an additional 20 h. The levels of IL-1β and TNF-α in the supernatants were measured by ELISA. The ELISA data are expressed as the mean ± SD of four separate experiments. * and *** indicate significant differences at the levels of p < 0.05 and p < 0.001, respectively, compared to S. sonnei-infected cells (A) or live S. sonnei-infected cells (C) or as indicated (B). ###indicates significant differences at the levels of p < 0.001 compared to sh-SC cells [one-way ANOVA with Dunnett's multiple comparisons test in panels (A,C); two-tailed t-test in panel (B)].