Objective To express the recombinant IL-37b protein and to investigate its role in the regulation of immune responses. Methods The prokaryotic expression vector pET28/IL-37b was constructed. The recombinant IL-37b protein was induced to be expressed and was purified using Ni²⁺-NTA gel column. C57BL/6 J mice were treated with IL-37b and injected with lipopolysaccharide (LPS) to induce septic shock, and the expression levels of IL-1β, IL-6, IFN-γ in the serum of the mice were detected. Dendritic cells from bone marrow of the mice were isolated and cultured, and were treated with IL-37b. After LPS-induced activation, the expression levels of marker molecules such as CD40, CD80 and MHCⅡ on the cell surface, and cytokines such as IL-1β, IL-10, IL-12 and TNF-α in the culture supernatants were detected by flow cytometry. The CD4⁺ T cells from mice were isolated and the inhibitory effects of IL-37b on the expression of IFN-γ, TNF-α and IL-10 in the culture supernatants of T cells after induction by LPS were detected. Results IL-37b reduced the expression levels of proinflammatory cytokines in the serum of septic shock mice. IL-37b also inhibited the expression of co-stimulatory molecules and proinflammatory cytokines of the mouse dendritic cells, and suppress the activation of CD4⁺T cells in vitro. Conclusions Purified recombinant IL-37b protein has high bioactivity, and can alleviate septic shock in organisms through inhibiting the activation of dendritic cells and related T cell immune responses.