FACS analyses of siglec-5 expression on human hematopoietic cells in comparison to CD33. (A) COS-1 cells transiently transfected with either full-length CD33 cDNA or siglec-5 cDNA and labeled with preimmune serum, mouse anti–siglec-5 antiserum or anti-CD33 MoAb followed by phycoerythrin-conjugated F(ab)₂anti-mouse IgG. Values refer to the percentage of cells within the indicated gate. (B) Human myeloid leukemic cell lines stained with either preimmune serum (open histograms), anti–siglec-5 antiserum or anti-CD33 MoAb (filled histograms). The mean fluorescence intensities observed with either anti–siglec 5 or anti-CD33 antibodies are shown in each box. (C) Human blood leukocytes, stained as described above for (B).