CS1 expression in MM cell lines and patient MM cells. (A) MM1S, MM1R, and H929 MM cell lines were washed and immunostained with anti-CS1 (mouse clone 235614)-PE (green histogram), -CD138-PE (red histogram), or -isotype control IgG₁ (iso IgG₁)-PE. Open histograms to the left of each panel are for iso IgG₁. (B) Immunostaining with a chimeric anti-CS1 ChLuc90 mAb (red histogram) or control human IgG (open histogram) was performed in 9 MM lines. (C) Total RNA isolated from CD138-purified tumor cells of each MM patient was subjected to microarray analysis using Affymetrix U133 Plus 2.0 array data. Three probes for CS1 and 2 probes for CD138 are indicated. (D) Expression of both CS1 (PE) and CD38 (FITC) in CD138-purified MM patient cells is shown (top). Open histograms represent iso IgG₁, whereas solid histograms are for indicated antigens (bottom). (E) Immunostaining with ChLuc90 mAb or iso IgG₁ in patient MM cells. Open and solid histograms represent iso IgG₁ and CS1, respectively. 293tflagCS1 overexpressing CS1 was used as a positive control.