PBMC from IGRA- (n = 7) or IGRA+ (n = 7) subjects were exposed to 0 (no PM), 0.1, 1 and 10 μg/ml of R2.5, CD2.5, WD2.5, R10, CD10, or WD10 at 37ºC, 5% CO2 in a humidified environment for 20 h. Following Exposure to PM, PBMC were infected with M.tb at MOI1 or left uninfected (A, B, C, and D) and incubated for additional 20 h. Frequencies of IL-1β-producing PBMC were examined by ELISPOT assays (see Materials and Methods). Results are shown as means ± SEM. Statistically significant (p≤0.05) dose-dependent changes relative to unexposed control PBMC is shown with solid lines. Statistically significant differences between seasons are shown with dotted lines.