FIG 4.
IL6 expression and secretion in response to stimulation of differentiated THP-1 cells with live toxigenic V. cholerae O1. IL6 expression (A) and secretion (B) in response to stimulation with CT, CTB, live V. cholerae N16961 (Live VC), live V. cholerae ΔctxAB JBK70 (Live ΔVC), inactivated V. cholerae N16961 (Inactivated VC), inactivated V. cholerae N16961 plus CT (Inactivated VC+CT), inactivated V. cholerae N16961 plus CTB (Inactivated VC+CTB), and live V. cholerae ΔctxAB JBK70 plus CT (Live ΔVC + CT). Horizontal bars represent mean values across multiple biological replications of the cell culture stimulation experiment, and error bars represent standard errors of the means. Expression was determined by qRT-PCR analysis of the IL6 gene using cDNA from THP-1 cells after 24 h of stimulation. Expression levels were quantified relative to those of an unstimulated control (medium) and the ACTB housekeeping gene (β-actin) using the ΔΔCT method of qRT-PCR analysis, expressed as fold change on a logarithmic scale. IL-6 secretion from THP-1 cells was determined by ELISA using supernatants collected after 24 h of stimulation. IL-6 protein concentration is represented in picograms of the supernatant per milliliter. **, P < 0.01; *, P < 0.05 (by paired nonparametric testing).