The maturation of dentritic cells (DCs) was a key role in initiating immune responses. Naturally occurring regulatory T cells (nTregs) might decrease DC maturation and stimulatory function through immunoregulatory cytokines such as IL-10 and inhibitory signalings such as cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and lymphocyte-activation gene 3 (LAG3). In our laboratory, we found that splenic B cells without additional cytokines or chemicals induced the generation of Treg-like cells which referred to as Treg-of-B cells. Treg-of-B cells suppressed the proliferation of T cells, showed high expressions of LAG3 and CTLA-4, and did not express Foxp3. In this study, we aim to investigate the effect of Treg-of-B cells on the development and functions of dendritic cells. After incubation with Treg-of-B cells for 24 hr, LPS treated DCs reduced productions of cytokine including IL-6 and TNF-α and expressions of costimulatory molecules including CD80 and CD86. To determine mechanisms of inhibitory effects, administrations of transwells and blocking antibodies against CTLA-4 and LAG3 were used into cell incubation. The data showed the inhibitory effect was dependent on cell-cell contact manner via CTLA-4 pathway. In conclusion, Treg-of-B cells might regulate immune responses partly through modulation of DC functions.