B. anthracis PGA elicits lower signals than B. subtilis PGA and B. licheniformis PGA in a human TLR2 assay. 50, 250, and 500 μg/ml B. anthracis PGA, B. licheniformis PGA, or B. subtilis PGA were tested in a TLR2 assay. Mean data for four experiments are presented as ligand/vehicle ratios ± SEM (n = 4). Statistical significance of signal for each dose of PGA above its vehicle control was determined by t tests comparing the mean treatment/background ratios. Statistical significance of differences between the PGAs were determined by t tests comparing mean ligand/vehicle ratios. No significant responses were observed at 50 μg/ml for any of the PGAs (data not shown). *p < 0.05, **p < 0.01, ***p < 0.0001. Ba, B. anthracis; Bl, B. licheniformis; Bs, B. subtilis.