Different levels of CD52 antigen expression evaluated by quantitative fluorescence cytometry are detected on B‐lymphocytes, CD 34⁺ cells and tumor cells of patients with chronic B‐cell lymphoproliferative diseases

Background: The success of treatment using monoclonal antibodies in oncology is influenced by, among other factors, the level of target antigen expression on tumor cells. The authors analyzed the intensity of the CD52 antigen expression in patients with chronic lymphoproliferative diseases and compared them with B‐lymphocytes of a healthy population and CD34 + cells in peripheral blood stem cells (PBSC) grafts. Methods: Recently diagnosed and previously untreated patients with B‐cell chronic lymphocytic leukemia (B‐CLL), mantle‐cell lymphoma (MCL), or small lymphocytic lymphoma (SLL) were evaluated and compared with control group and CD34 + cells. The intensity of CD52 was expressed in molecules of equivalent soluble fluorochrome units (MESF) and antibody‐binding capacity (ABC). Results: In the group of patients with B‐CLL, the CD52 level on tumor cells (245 × 10 3 MESF; 107 × 10 3 ABC) was significantly lower than on B‐lymphocytes of the control group (446 × 10 3 MESF; 194 × 10 3 ABC; P < 0.001) and SLL tumor cells (526 × 10 3 MESF; 229 × 10 3 ABC; P < 0.001). The CD52 antigen was expressed on a majority of CD34 + cells, but its expression intensity was low (101 × 10 3 MESF; 44 × 10 3 ABC). Conclusions: Our data demonstrate differences in the intensity of the CD52 antigen expression between B‐lymphocytes and tumor lymphocytes of B‐CLL patients, and between B‐CLL and SLL tumor cells. CD52 antigen is expressed at low level on CD34 + cells.