Expression and identification of ULBP4. (A) Purified rULBP4 was analyzed by SDS-PAGE (i) and detected with anti-ULBP4 mAb (ii) or anti-Histag mAb (iii). (B) IFN-γ secretion of NK92 cells after stimulation with purified rULBP4 or control other human recombinant proteins (NG). Data represent means ± SD (error bars) of 3 independent experiments. (C) Flow cytometric staining of untransfected and ULBP4-transfected EL4 cells with anti-ULBP4 mAb 8C9 (black line histogram). Ig controls are shaded. (D) Expressions of ULBP4 transcripts in ULBP4-transfected and untransfected EL4 cells were detected by RT-PCR.