CTLA-4 is expressed in cutaneous melanoma cell lines and it is recognized by Ipilimumab. Flow cytometric profiles of representative primary cell lines and established cell lines (C32, MeWo, FO-1), stained with either an anti-CTLA-4 polyclonal antiserum (surface) and 14D3 mAb (cytoplasm) (panel A) or Ipilimumab Ab (panel B). FO-1 cell line was used as control for CTLA-4 surface negative expression. Open histograms represent staining with specific anti-CTLA-4 Abs, filled histograms represent staining with isotype control Abs. Numbers within the quadrants represent values of MRFI. Panel C, densitometric analysis of RT-PCR for CTLA-4 transcripts (TM and delTM) normalized to GAPDH and reported as % of expression. The experiment was repeated three times with similar results. Panel D, ELISA analysis of sCTLA-4 in melanoma cell SN. Results are means ± SD of two independent experiments performed in duplicate.