title: Rituximab-mediated antibody-dependent cellular cytotoxicity against neoplastic B cells is stimulated strongly by interleukin-2.
abstract: 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.
authors.affiliation: Department of Immunology and Cell Biology, Istituto Ricerche Farmacologiche Mario Negri, via Eritrea 62, 20157 Milan, Italy. golay@marionegri.it
authors.forename: Josée
authors.initials: J
authors.lastname: Golay
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Manganini
authors.forename: Valeria
authors.initials: V
authors.lastname: Facchinetti
authors.forename: Rosanna
authors.initials: R
authors.lastname: Gramigna
authors.forename: Raewyn
authors.initials: R
authors.lastname: Broady
authors.forename: Gianmaria
authors.initials: G
authors.lastname: Borleri
authors.forename: Alessandro
authors.initials: A
authors.lastname: Rambaldi
authors.forename: Martino
authors.initials: M
authors.lastname: Introna
mesh_terms: 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
chemical_list: D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; D000912:Antibodies, Neoplasm; D000970:Antineoplastic Agents; D007376:Interleukin-2; D000069283:Rituximab