Physiological context of HLA-DR recognition by γδ TCRs. (A) Staining for HLA-DR expression on fibroblasts treated with recombinant IFN-γ. (B) Coculture of JE6.1 reporter cells expressing TCR02, TCR04, or TCR05 with untreated fibroblasts or fibroblasts stimulated for 24 h with IFN-γ. Medium with IFN-γ was removed prior to the addition of reporter cells. (C and D) Parallel staining of γδ T cells from PBMCs with PE- and APC-labeled HLA-DRB1*03 tetramers presenting CMV-derived peptides. (C) Representative dot plots gated on CD3⁺/CD19⁻ (first left), γδ T-cells (second left and right), and Vδ1⁺ (second right). PE⁺/APC⁺ cells are highlighted in red in the right dot plot. (D) Frequencies of PE⁺/APC⁺ (tetramer double-positive) cells. Presented peptide from CMV-encoded proteins IE1 or IE2 (for sequence details, see Fig. S3 C).