Exosomes isolated from mycobacteria-infected THP-1 cells can induce a TLR/MyD88-dependent proinflammatory response in naive macrophages. (A) C57BL/6 BMMs were treated with 10 μg of exosomes isolated from uninfected, M bovis BCG–infected, or H37Rv-infected THP-1 cells. Western blot analyses were performed on cell lysates obtained 24 hours after exosome treatment using antibodies specific for phosphorylated p38 or IκBα. Total p38 was used as a loading control. Data are representative of 2 separate experiments. TLR2^−/− (B), TLR4^−/−, (C) or MyD88^−/− (D) and the corresponding BALB/c or C57BL/6 WT BMMs were treated with the indicated concentrations of the different exosome preparations, and TNF-α levels were measured 24 hours after exosome treatment by ELISA. Data are representative of 2 independent experiments and are expressed as means plus or minus standard deviation of duplicate wells.