HLA DR4 allotype recognition by TRAT-specific CD8⁺ T cells is mediated through TRBV13 and is not dependent on CD8 interaction with TcR. (A) TRAT-specific T cells were exposed to peptide-coated and -uncoated HLA Cw*0602⁺ and DRB*0401⁺ LCLs and assessed for IFN-γ expression by the use of ICS assays. These T cells were also stained with a panel of anti-TRBV antibodies. Data from 2 of the anti-TRBV antibodies that showed positive staining are shown in this figure. T cells positive for TRBV13 showed IFN-γ expression after exposure to peptide-coated and -uncoated HLA Cw*0602⁺ and DRB*0401⁺ LCLs (right panels) and TRBV4-3⁺ T cells expressed IFN-γ after exposure to peptide-coated HLA Cw*0602⁺ and DRB*0401⁺ LCLs only. (B) TRAT-specific T cells were exposed to peptide-coated and -uncoated HLA Cw*0602⁺ and DRB*0401⁺ LCLs in the presence or absence of anti-CD8 antibody and then assessed for IFN-γ expression by the use of ICS assays. These T cells were costained with TRBV-specific antibodies to identify TRBV4-3- and TRBV13-positive populations. Data presented in the left and panel show IFN-γ expression by TRAT-specific T cells after incubation with peptide-coated LCLs. The right panels show IFN-γ expression by TRBV13-positive TRAT-specific T cells in the presence or absence of anti-CD8 antibody.