FIG. 1.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a general inhibitor of the 3′IghRR. CH12.γ2b-3′IghRR cells were treated with increasing concentrations of TCDD (0–30 nM) and cotreated with the following toll-like receptor ligands: A, R848 (1 μg/ml); B, CpG (1 μM); or A and B, LPS (1 μg/ml). The LPS and TCDD cotreatment served as a positive control for TCDD-induced inhibition of the 3′IghRR. 3′IghRR-regulated γ2b transgene expression (n = 3 per treatment group) normalized to 2 μg total protein was determined by enzyme-linked immunosorbent assay. Results were normalized to the appropriate vehicle control set to 100%, ie, cotreatment of 0.01% dimethyl sulfoxide (vehicle control denoted as 0.0 nM TCDD) and stimulation. The means from 3 separate experiments (overall mean ± SE) are represented in the bar graph. The stimulation index for LPS, R848, and CpG did not differ significantly and was approximately 3-fold above the unstimulated, naive control. Statistical significance was determined by a 1-way ANOVA followed by Dunnett’s Multiple Comparison test. “**” and “***” denote significance from the vehicle control (0.0 nM TCDD) at P < .01 and P < .001, respectively. R848, Resiquimod; CpG, cytosine-phosphate-guanine (TLR9 agonist); LPS, lipopolysaccharide (TLR4 agonist); 3′IghRR, mouse 3′Igh regulatory region.