Induction of HLA-G26–40-specific CD4+ T cell responses. (A) CD4+ T cell clones (G1; HLA-DR4/DR9/DR53, G2; HLA-DR4/DR9/DR53, G3; HLA-DR9/DR53 and G4; HLA-DR1/DR15) were tested for their capability to respond to various concentrations of HLA-G26–40 peptide using autologous PBMCs as APCs. (B) Inhibition of HLA-G26–40-specific CD4+ T cell responses by anti-HLA-DR mAb L243 but not by anti-HLA class I mAb W6/32 (negative control) (*p < 0.05, Student's t test). (C) CD4+ T cell clones were evaluated using L-cells transfected with individual HLA-DR genes as APCs to determine the restricting HLA class II alleles (*p < 0.05, Student's t test). Supernatants were collected after 48 h of incubation and analyzed by ELISA for IFNγ production (*p < 0.05, one-way ANOVA with the Holm post-hoc test). Bars and error bars indicate the mean and SD, respectively. Experiments were performed in duplicate. (*p < 0.05, Student's t test). Bars and error bars indicate the mean and SD, respectively. Experiments were performed in duplicate.