B cells have been found to have phagocytic activity in recent years, but the studies exploring the regulation mechanisms are still lacking to date. In the present study, the recombinant interleukin-10 (rIL-10) was obtained to study the function of IL-10 on phagocytosis of flounder (Paralichthys olivaceus) mIgM+ B lymphocytes. Flow cytometric analysis showed that IL-10 significantly enhanced the phagocytosis of Edwardsiella tarda but not Lactococcus lactis by mIgM+ B lymphocytes. Moreover, significantly higher intracellular ROS levels were detected in mIgM+ B lymphocytes following rIL-10 stimulation. The qRT-PCR analysis showed that rIL-10 could upregulate the expressions of IL-10Rb and Stat3 in mIgM+ B lymphocytes, suggesting that IL-10 might modulate the phagocytosis of mIgM+ B lymphocytes by activating IL-10R and Stat3. In addition, we also found that the enhancing effect of IL-10 on phagocytosis and intracellular ROS levels of mIgM+ B lymphocytes were suppressed by the administration of niclosamide. These results collectively demonstrated that IL-10 enhanced mIgM+ B lymphocyte-mediated phagocytosis of E. tarda and intracellular bactericidal ability, and IL-10R and Stat3 might play a curial role in the regulation of IL-10-stimulated phagocytosis, which would deepen our understanding of regulation mechanism of B cell phagocytosis.,Copyright © 2019 Elsevier Ltd. All rights reserved.