Immunohistochemical staining for CD8 and NKG2A. Two consecutive sections of a colorectal carcinoma lesion displaying a strongly and homogeneously positive (MEM-E/02 score = 3) neoplastic mucosa were stained by mAb 1A5 to CD8 (A and C) and the polyclonal antibody N-19 to NKG2A (B and D). Different chromogens reveal CD8 and NKG2A cells in a large peritumoral infiltrate. Counterstaining with Haematoxilin. Magnification 10 × (panel A and B) and 20 × (panel C and D). Scale bar = 100 μm.