FIG. 2.

Effects of Y. pestis LPS-37 on cytokine production in U937 cells stimulated with TLR4 and TLR2 agonists. (A) U937 cells cultured in the presence of LPS-37 or compound 406 were stimulated with either Y. pestis LPS-27 (1 ng/ml) or Salmonella LPS (1 ng/ml). The cytokine levels in the culture supernatant were determined by ELISA. The data are presented as the means ± standard errors for triplicate samples. (B) U937 cells cultured in the presence of 10 ng/ml LPS-37 were stimulated with 1 ng/ml of LPS-27 or Salmonella LPS. Total RNA was isolated 2 h after stimulation and subjected to RT-PCR for determination of cytokine mRNA expression. PCR products were separated by electrophoresis on 1.2% agarose gels and stained with ethidium bromide. (C) U937 cells cultured in the presence of LPS-37 were stimulated with Pam3-Cys (10 nM), and cytokine production was determined as described for panel A. (D) U937 cells cultured with LPS-37 (10 ng/ml) were stimulated with Pam3-Cys (10 nM), and cytokine mRNA expression was determined as described for panel B. Representative results of three (A and C) or two (B and D) experiments are presented.