Galectin-9 in physiological and pathological conditions.

We first cloned galectin-9 (Gal-9)/ecalectin as a T cell-derived eosinophil chemoattractant. Gal-9 plays a role in not only accumulation but also activation of eosinophils in experimental allergic models and human allergic patients, because Gal-9 induces eosinophil chemoattraction in vitro and in vivo and activates eosinophils in many aspects. Gal-9 requires divalent galactoside-binding activity but not the linker peptide of Gal-9 to exhibit its biological functions, and an unidentified matrix metalloproteinase is involved in the release of Gal-9.