Bioassay guided fractionation of RPR. PBMac (5 × 105) were pretreated with 0.05% DMSO or the indicated RPR fractions (A) or RPR-EA subfractions (B) overnight and then stimulated with BCG (MOI = 1). Culture supernatants were collected after 24 hours. The levels of IL-10 in the supernatants were measured by ELISA. The IL-10 concentration in the supernatant of DMSO + BCG sample was set as 100%, and the rest were compared to it to obtain a percentage value. Results are shown as mean ± SD from independent experiments on PBMac obtained from three different healthy donors. *P < 0.05, **P < 0.001 compared to the DMSO + BCG sample (one-way ANOVA, Tukey's test).