The anti-lymphoma effect of antibody-mediated immunotherapy is based on an increased degranulation of peripheral blood natural killer (NK) cells.
BACKGROUND
In patients treated with rituximab and alemtuzumab for lymphomas or CLL, antibody-dependent cellular cytotoxicity (ADCC) is a major mechanism of action. Therefore, assessment of ADCC is mandatory to understand the complex mechanisms leading to the anti-lymphoma effects of monoclonal antibodies (mAb). Due to methodical difficulties, little is yet known about the relevant cell subpopulations and effector mechanisms leading to tumor lysis in ADCC.


METHODS
We used a novel flow cytometric assay that detects CD107a as a marker for NK-cell degranulation to characterize and quantify peripheral blood natural killer (NK) cells mediating ADCC in vitro and in vivo.


RESULTS
We observed specific and dose-dependent NK-cell activation after administration of rituximab and alemtuzumab. The number of degranulating NK cells was closely related to the concentration of mAb and the effector:target ratio. We were able to quantify and characterize the peripheral blood NK cells mediating ADCC. The majority of degranulating NK cells had the phenotype: CD56(dim), CD69(+), NKG2D(+), NKp30(-), NKp46(-), and CD94(-). Furthermore, we found that the CD107a assay can also visualize ADCC under clinical conditions as we observed increased numbers of NK cells degranulating in response to CD20(+) lymphoma cell lines in patients with non-Hodgkin's lymphoma treated with rituximab.


CONCLUSIONS
We were able to quantify and characterize NK cells mediating ADCC with a new and feasible method. The CD107a assay may be useful for predicting treatment responses of individual patients and may help find the optimal dosage and timing for treatment with mAb.
Fischer
Lars
L
Department of Hematology, Oncology and Transfusion Medicine, Charité-Campus Benjamin Franklin, Berlin, Germany.
Penack
Olaf
O
Gentilini
Chiara
C
Nogai
Axel
A
Muessig
Arne
A
Thiel
Eckhard
E
Uharek
Lutz
L
D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D058846:Antibodies, Monoclonal, Murine-Derived; D000920:Antibody-Dependent Cell Cytotoxicity / Q000187:drug effects* / Q000276:immunology; D000943:Antigens, Differentiation / Q000276:immunology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D015415:Biomarkers; D015550:Cell Degranulation / Q000187:drug effects* / Q000276:immunology; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D005434:Flow Cytometry; D006801:Humans; D007694:Killer Cells, Natural / Q000276:immunology*; D008228:Lymphoma, Non-Hodgkin / Q000188:drug therapy / Q000276:immunology*; D052118:Lysosomal-Associated Membrane Protein 1 / Q000276:immunology; D000069283:Rituximab
D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; D000943:Antigens, Differentiation; D000970:Antineoplastic Agents; D015415:Biomarkers; D052118:Lysosomal-Associated Membrane Protein 1; D000069283:Rituximab