Cross-recognition of HLA DR4 alloantigen by TRAT-specific T cells. (A) EBV-transformed LCLs expressing different HLA DR4 subtypes were used as APCs. After incubation these T cells were then analyzed for IFN-γ expression by the use of ICS assays. (B) TRAT-specific T cells were exposed to T2 cells expressing HLA DRB*0401 with or without peptide editor HLA DM and then assessed for IFN-γ expression by use of the ICS assay.