Rituximab-mediated antibody-dependent cellular cytotoxicity against neoplastic B cells is stimulated strongly by interleukin-2.
OBJECTIVE
We analyzed the sensitivity of freshly isolated neoplastic B cells to rituximab-mediated antibody-dependent cellular cytotoxicity (ADCC), using different effector cells.


METHODS
ADCC was performed by 51Cr release assays in vitro, using peripheral blood mononuclear cells, IL-2-activated or expanded NK cells, neutrophils or macrophages as effector cells. B lymphoma lines and freshly isolated leukemic samples were used as targets.


RESULTS
NK cells, but PMN or macrophages mediated rituximab dependent cellular cytotoxicity against two B lymphoma lines. Purified NK cells (95% CD56+/CD16+) reached 70% lysis at the highest E:T ratio. By contrast, all freshly isolated B leukemia or lymphoma cases, including 5 chronic lymphocytic leukemia, 1 B-prolymphocytic leukemia, 1 mantle cell lymphoma, 2 marginal zone lymhomas and 2 follicular lymphomas were poorly lysed by ADCC in the same conditions and regardless of CD20 expression levels, reaching a mean of 4% and 27% maximal lysis with PBMC or purified NK cells, respectively. Interestingly, short term IL-2 cultured PBMC, containing 10 % activated NK cells, as well as long-term expanded NK cells, containing 80-95% activated NK cells, became strong ADCC effector cells with rituximab and lysed all leukemic samples to a mean of 57% and 67% at the highest E:T ratio, respectively.


CONCLUSIONS
Primary leukemic cells are more resistant than cell lines to rituximab- and NK cell-mediated ADCC but short-term exposure to IL-2 or long-term expansion of NK cells in vitro may provide effective tools to improve the therapeutic activity of rituximab.
Golay
Josée
J
Department of Immunology and Cell Biology, Istituto Ricerche Farmacologiche Mario Negri, via Eritrea 62, 20157 Milan, Italy. golay@marionegri.it
Manganini
Massimiliano
M
Facchinetti
Valeria
V
Gramigna
Rosanna
R
Broady
Raewyn
R
Borleri
Gianmaria
G
Rambaldi
Alessandro
A
Introna
Martino
M
D000911:Antibodies, Monoclonal / Q000276:immunology / Q000494:pharmacology*; D058846:Antibodies, Monoclonal, Murine-Derived; D000912:Antibodies, Neoplasm / Q000276:immunology / Q000494:pharmacology; D000920:Antibody-Dependent Cell Cytotoxicity / Q000187:drug effects* / Q000276:immunology; D000970:Antineoplastic Agents / Q000276:immunology / Q000494:pharmacology; D045744:Cell Line, Tumor; D006801:Humans; D007376:Interleukin-2 / Q000276:immunology / Q000378:metabolism*; D020014:K562 Cells / Q000187:drug effects / Q000276:immunology; D015448:Leukemia, B-Cell / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D016393:Lymphoma, B-Cell / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D000069283:Rituximab
D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; D000912:Antibodies, Neoplasm; D000970:Antineoplastic Agents; D007376:Interleukin-2; D000069283:Rituximab