Analysis of CD56 and S100 expression in CTLA-4 positive melanoma cell lines. Panel A, cytofluorimetric analysis of direct and indirect immunofluorescent co-stainings performed with a PE-conjugated anti-CD56 (NCAM) and Ipilimumab Abs, as shown for representative cell lines. Numbers within the quadrants represent the percentage of Ipilimumab/CD56 double positive melanoma cells. Panel B, immunohistochemical staining with anti-S100 mAb and with anti-CD20 mAb used as isotype-matched irrelevant antibody providing the negative control (CTR), as shown for representative cell lines. Images were taken using magnification 400×. Scale bar, 20 micron.