Expression of TAP-1, TAP-2 and HLA-I in NPC and normal nasopharyngeal tissue samples. Staining for the three proteins was performed as described in Materials and methods. NPC tissues exhibited weak positive or absent staining for (A) TAP-1, (C) TAP-2 and (E) HLA-I (magnification, ×400). Normal nasopharyngeal tissues exhibited strong staining for (B) TAP-1, (D) TAP-2 and (F) HLA-I (magnification, ×400). TAP, transporters associated with antigen processing; HLA, human leukocyte antigen; NPC, nasopharyngeal carcinoma.