To investigate the function of Gal-9 in B cells during EBV infection, we first applied exogenous human recombinant Gal-9 (hrGal-9) and Gal-9 neutralizing antibody (Gal-9 MAb) to the culture medium, and we found that hrGal-9 accelerated B-cell proliferation of EBV-infected B cells at an early stage of the transformation process (days 3, 5, and 7) following EBV infection. This evidence concerns the gene LGALS9 and Epstein-Barr virus infection.