Galectin-3 restrains T cell-driven inflammation in the testis and epididymis.

Galectin-3 (Gal-3) is a pleiotropic molecule involved in immune regulation and tissue homeostasis. While it has been implicated in reproductive tissue function, its role in shaping immune cell dynamics within the testis and epididymis remains incompletely defined. Here, we investigated the function of Gal-3 in the testis and epididymis under steady-state and inflammatory conditions, to determine its contribution to inflammatory responses and tissue damage. In both murine and human tissues, Gal-3 frequency and staining intensity increased along the testicular-epididymal axis, with the highest proportion of Gal-3+ cells in the cauda epididymidis, where it was detected across multiple murine immune cell populations, as well as epithelial and germ cells. Consistent with this distribution, Gal-3 deficiency reshaped the local immune landscape, leading to reduced macrophage populations and increased T cell abundance in the testis and cauda epididymidis. In a model of experimental autoimmune epididymo-orchitis (EAEO), Gal-3-deficient (Lgals3-/-) mice exhibited exacerbated inflammation, fibrosis, and irreversible organ damage, accompanied by increased T cell frequencies among CD45+ cells. Transcriptomic analysis revealed enhanced T cell activation signatures, particularly involving IFN-γ-related pathways. Functionally, Gal-3-deficient T cells showed increased cytokine production, specifically IFN-γ, which was further amplified in the presence of Gal-3-deficient macrophages, which in turn acquired a pro-inflammatory phenotype. Together, these findings identify Gal-3 as a key regulator of T cell activity and macrophage polarization with prominent effects in the testis and epididymis, with implications for understanding immune-mediated infertility.