Traditional Korean Doenjang Restores Splenic and NK Cell Function in Cyclophosphamide-Induced Immunosuppressed Rats.

Fermented soybean-based foods contain diverse bioactive compounds with recognized health benefits. Among them, doenjang is widely consumed in East Asia and has been associated with protective effects against several disorders, including immunosuppression. This study evaluated the immunoenhancing effects of doenjang sourced from four regions of Korea in cyclophosphamide (CP)-induced immunosuppressed rats. Four-week doenjang administration restored spleen weight and improved hematological parameters, including white blood cell, lymphocyte, neutrophil, and monocyte counts. Additionally, doenjang intake enhanced immune function, as evidenced by increased splenic natural killer cell activity, increased splenocyte proliferation under lipopolysaccharide- and concanavalin A-stimulated conditions, and higher levels of interleukin (IL)-2, IL-12, interferon-γ, and immunoglobulin G. Furthermore, the suppressed phosphorylation of mitogen-activated protein kinases/nuclear factor kappa B signaling was recovered, accompanied by improved splenic structure. Collectively, our findings demonstrate that the regional varieties of doenjang effectively mitigate CP-induced immune dysfunction, indicating their potential as functional dietary interventions.