Soluble galectin-1 positively impacts on the infection of T cell line and PBMCs by HTLV-I-envelope-pseudotyped viruses. Jurkat cells (A, B) or PBMCs (C) (1 × 105 cells) were infected with 10 ng (p24) of HTLV-I envelope-pseudotyped HIV-1 viruses in the presence of different concentrations of purified galectin-1 (0–4 μM), with or without lactose (50 mM). B, Jurkat cells were also treated with TNF-α (10 ng/ml). Luciferase activities were measured 48 hours post-infection. The results represent three independent infections and are expressed as the mean luciferase activity value +/- standard deviation (*p < 0.05; **p < 0.01).