Immunoperoxidase staining showing HLA-E expression in human normal tissues. (A) Comparative staining for HLA-E (i, iii, v) and HLA-G (ii, iv, vi) in paraffin-embedded sections of human first-trimester trophoblast (i-ii) and kidney (iii-vi). (B) Comparative expression of HLA-E protein was studied in paraffin-embedded sections of human spleen (i-ii) and lymph node (iii-iv). Arrowheads indicate ECs, M, macrophages; MK, megakaryocytes; and sEC, sinusoidal ECs. Original magnification, ×400. Images were visualized under an Olympus BX50F4 microscope (Olympus Optical, Tokyo, Japan) equipped with 4×/0.13, 10×/0.30, 20×/0.50, and 40×/0.75 objective lenses and an Olympus Camedia C-4040Zoom camera; Olympus DP-Soft version 3.2 software was used to acquire and process images.