PBMC expression and biochemical features of mAb 256 ligand(s). (A) Surface expression of Ag#256 on NK cells (CD3⁻, CD56⁺), T cells (CD3⁺), B cells (CD19⁺), and monocytes (CD14⁺) within ex vivo human PBMCs was analyzed by flow cytometry (mAb 256, 10 μg/mL). Values for the frequency of Ag#256⁺ cells within each total cell subset are indicated in the quadrants (gated events). Results are representative of at least 3 independent experiments performed with PBMCs of different donors. (B) Surface expression of Ag#256 (green staining) was analyzed on Raji cells by confocal microscopy. Scale bar represents 5 μm. No significant staining was detected when purified mouse IgG1 (isotype control) was used as the primary mAb. (C) Cell lysates of human B-LCL (Do#AD), C91 T2.2, and Daudi cell lines were analyzed by immunoblotting using mAb 256 as primary mAb.