The biological activities of 7 microbial extracellular glycolipids including mannosylerythritol lipid (MEL)-A, MEL-B, polyol lipid (PL), rhamnolipid (RL), sophorose lipid (SL), succinoyl trehalose lipid (STL)-1, and STL-3 were investigated. All glycolipids except for RL were found to induce cell