Figure 2.

Y. pestis (Yp) can modulate the activation of TLR4 depending on its growth temperature. Strains of Yp were grown at 27−28°C or 37°C and suspended in PBS. Different amounts of cells were added to HEK293-TLR2 or -TLR4 cells to evaluate their ability to activate the TLRs. Yp strains used: (A) Yp CO92, wild-type; (B) Yp C12, a F1- or capsule negative strain; (C) Yp EV76, a vaccine strain;. Media controls contained only PBS, and positive controls contained either HKLM cells (2 x 10⁶ cells) for TLR2 or E. coli LPS (0.2 ng) for TLR4. All samples were analyzed in triplicate, and results represent one of two independent repeats. Results are presented as geometric mean with standard error of the mean. Significant differences between values at different temperatures are shown above the results. Significant values compared to media control are shown: *P ≤ 0.05; **P ≤ 0.01; ***P ≤ 0.001; ****P ≤ 0.0001; *****P ≤ 0.00001.