The Pep-9 –induced activation of the CD4+ T cell lines, i.e. generated to SPANX-B protein (A), or Pep-5 (B), or Pep-9 (C) can be abrogated by the presence of anti-HLA-DR Ab. In contrast, the presence of antibodies to HLA-DQ, or HLA-DP or MHC class I (anti-HLA-A,B,C) did not affect activity of CD4+ T cells. ***P<0.001 value is for comparison with the group indicated by line. Shown, mean ± SEM of representative and reproducible results of two independent experiments performed in triplicates for each panel.