Figure 2

OX40 is specifically expressed on the surface of T cells naturally infected with HTLV-1 that have the potential to produce pro-inflammatory cytokines. A. OX40 was detected on CD4⁺ T cells of HAM/TSP patient with anti-OX40 mAb (clones B-7B5) after 16 hours in vitro cultivation in the absence of any growth factors or mitogen. B. OX40L was not detected on CD4⁺ T cells of HAM/TSP patient with anti-OX40L mAb (clones 5A8) after 16 hours in vitro cultivation in the absence of any growth factors or mitogen. C. Tax protein was detected in CD4⁺ T cells of HAM/TSP patient after 16 hours in vitro cultivation. D. OX40 was expressed almost exclusively in naturally infected CD4⁺ T cells that also expressed Tax in HAM/TSP patient. E. Both HTLV-1 tax and OX40 mRNA expression in CD4⁺ T cells was increased after 16 hours in vitro cultivation. F. The frequency of pro-inflammatory cytokine positive cells within the OX40⁺CD4⁺ and Tax⁺CD4⁺ populations from HTLV-1 infected individuals are significantly higher than OX40^-CD4⁺ and Tax^-CD4⁺ T cells, respectively (p<0.001, Student’s t- test). One representative experiment of HAM/TSP patient (HAM/TSP1) is shown.