Immunohistochemical staining of formalin-fixed, paraffin-embedded colorectal carcinoma tissues. A-C: Representative reactivity scores of MEM-E/02 to HLA-E (see Materials and Methods): A = 1, B = 2, C = 3. D: staining of lymphoid infiltrates with an antibody to the HLA-E-specific receptor NKG2A. Magnification: 10×, 40×, 20×, and 40× respectively. Scale bar = 100 μm.