Genistein and the immune system: experimental evidence, key challenges, and future perspectives.

Genistein (GEN), a soy-derived isoflavonoid and phytoestrogen, exhibits diverse biological activities against allergic and hypersensitivity reactions, autoimmune disorders, infectious diseases, and cancer. Its immunomodulatory properties are crucial to these effects; however, clinical translation remains limited due to the complexity and pronounced context dependence of its immune actions. This review critically summarizes experimental evidence on GEN-mediated immunomodulation across innate and adaptive immune systems, including its effects on cytokine regulation and key molecular signaling pathways. GEN has been shown to modulate dendritic cells, mast cells, macrophages, T cells, B cells, and natural killer cells through both estrogen receptor-dependent and -independent mechanisms, involving pathways such as ERK, NF-κB, p53, and IL-18 receptor signaling. Notably, these immunomodulatory effects are influenced by multiple variables, including cell type, dose, sex, hormonal milieu, and developmental stage, presenting significant challenges for clinical translation. While GEN demonstrates substantial immunomodulatory potential, its highly context-specific actions necessitate disease-relevant preclinical validation and carefully tailored therapeutic strategies that account for dosage, target immune cells, hormonal status, and patient sex. Addressing these factors, together with advances in formulation approaches to improve bioavailability, will be essential for the rational development of GEN as a precision immunomodulatory agent.