Galectin-9 (Gal-9) is a member of animal lectins that have an affinity to ß-galactosides and Forssman pentasaccharide. It is strongly overexpressed in Hodgkin's disease tissue and it might participate in the interaction between the H&RS cells with their surrounding cells and might thus play a role in the pathogenesis of this disease and/or its consistently associated immunodeficiency.