Production of TNFα and IL-12 upon challenge with gonococci expressing sialylated LOS. Bacterial LOS was analyzed via polyacrylamide gel electrophoresis. (A) LOS samples shown (from left): wild type F62, F62ΔlgtD, and F62ΔlgtD grown in the presence of CMP-NANA (sialylated). (B) THP-1 cells (1 × 106/ml) were challenged with sialylated and unsialylated N. gonorrhoeae. Cytokine production in sample supernatants was measured by ELISA. Left panel: IL-12 levels after an 18 hour challenge of THP-1 cells (1 × 106/ml) with 1 × 102/ml live N. gonorrhoeae. Right panel: TNFα levels after 7 hour challenge of THP-1 cells (1 × 106/ml) with 1 × 108 gentamicin-killed gonococci. (S) Represents sialylated samples (grown in the presence of CMP-NANA). Challenge with media alone did not result in measurable production of IL-12 or TNFα.