Western blot detection of galectin-9 isoforms using the 1G3 monoclonal antibody. A low amount of S and M galectin-9 isoforms are present in wild-type HeLa cells. These isoforms are readily detected following transfection with the appropriate expression plasmids. The L-isoform is expressed at a lower abundance than the two other forms. The three endogenous isoforms are detected in the protein extracts from the C15 and C666-1 NPC xenografts. The EBV-positive B-cell line REMB1 expresses a high amount of the M-isoform and a very low amount of L-isoform, however no S-isoform could be detected. In contrast with REMB1 cells, the BL2 cells derived from an EBV-negative B-cell lymphoma have no detectable galectin-9. The faint background bands visible after long exposure do not match with any galectin-9 isoform.