Enhancing immunity is essential for the maintenance and restoration of body homeostasis, facing the pandemic of coronavirus disease 2019 (COVID-19), and combatting the effects of an unbalanced lifestyle^[1]. Previous research has proven that dietary fibers have multiple bioactivities, indicating their great potential in functional food development^[2,3].

In this study, the immunomodulatory activity of three dietary fibers on cyclophosphamide (CTX)-induced immunosuppression are investigated from the perspective of humoral immunity. We compared the changes in mouse body weight, thymus or spleen index, IgM secretion and metabolism in serum, splenic cytokine TNF-α secretion, splenic mRNA expression of GATA-3 and T-bet detected by quantitative real-time PCR (RT-PCR), and the percentage of CD3⁺ cells in splenic lymphocytes using flow cytometry. The results show that all three dietary fibers improved the status of immunosuppressed mice by recovering body weight and relative organ weight as well as increasing the secretion of serum IgM and splenic cytokine TNF-α. Among the three dietary fibers, apple pectin mostly enhanced T-bet levels, regulating the balance of Th1/Th2 cells^[3]. In addition, the percentage of CD3⁺ cells in splenic lymphocytes improved significantly after treatment with inulin and guar gum. Our research compared the immunomodulatory bioactivity of three different dietary fibers in a CTX-induced immunosuppressed mice model, providing evidence for the bioactivity potential of dietary fibers and a view of integrated immunometabolic responses.