CTLA-4 is expressed in cutaneous melanoma tissues and it is recognized by Ipilimumab. Immunohistochemical (IHC) analysis is shown in a representative metastatic melanoma lesion (ML). IHC staining with murine anti-CTLA-4 14D3 mAb of METR-ML (A) was detected with AP-conjugated secondary antibody and Fast Red chromogen (red staining). IHC staining with Ipilimumab of METR-ML (B) was detected with HRP-conjugated secondary antibody and DAB chromogen (brown staining). IHC staining with anti-S100 mAb was used as positive control as shown in the representative METR-ML (C) sample. IHC stainings with a murine anti-CD20 mAb and human Rituximab anti-CD20 mAb were used as isotype negative controls for 14D3 and Ipilimumab, respectively, as shown for METR-ML (D,E). Images were taken using magnification 630×. Scale bar, 50 micron.