title: B-lymphoma cells escape rituximab-triggered elimination by NK cells through increased HLA class I expression.
abstract: OBJECTIVE
  Antibody-dependent cellular cytotoxicity (ADCC) by natural killer (NK) cells is a major effector mechanism of the monoclonal anti-CD20 antibody rituximab in eliminating B-cell lymphomas. Resistance to this treatment occurs, although CD20 antigen is expressed on the tumor cells.
  
  
  METHODS
  A model of ADCC was established by stimulating human bulk NK cells and inhibitory killer immunoglobulin receptor (KIR)-defined NK cells from human leukocyte antigen (HLA)-typed donors. NK-cell activation was triggered via stimulation of the Fc receptor with immunoglobulin G aggregates, rituximab-labeled HLA-defined CD20-positive B-lymphoblast cell lines or CD20-positive B-lymphoma cell lines. The effect of KIR ligation by anti-KIR antibodies and HLA, the HLA expression density and rituximab concentrations on the efficacy of ADCC were analyzed in granzyme B ELISPOT measuring NK-cell activation and fluorescein-activated cell sorting cytotoxicity assay.
  
  
  RESULTS
  HLA, but not CD20 expression density correlated with NK-cell activity against rituximab-labeled targets. ADCC was increased or decreased following HLA shielding or KIR activation by anti-KIR antibodies, respectively. Herein we show that rituximab-induced ADCC is attenuated upon ligation of KIR by HLA molecules expressed on human B-lymphoma target cells. Moreover, anti-KIR antibodies do not only block KIR/HLA interactions, but display agonistic effects at the KIR, which has to be considered for therapeutical applications.
  
  
  CONCLUSIONS
  KIR activation and HLA expression density are critical determinants for the efficacy of rituximab treatment. An explanation for the failure of rituximab treatment may be the protection of the tumor cells from ADCC by inhibiting NK-cell function with their surface HLA.
authors.affiliation: Department of Haematology and Oncology, Georg-August University of Göttingen, Göttingen, Germany. a.borgerding@med.uni-goettingen.de
authors.forename: Andrea
authors.initials: A
authors.lastname: Borgerding
authors.forename: Justin
authors.initials: J
authors.lastname: Hasenkamp
authors.forename: Michael
authors.initials: M
authors.lastname: Engelke
authors.forename: Nina
authors.initials: N
authors.lastname: Burkhart
authors.forename: Lorenz
authors.initials: L
authors.lastname: Trümper
authors.forename: Jürgen
authors.initials: J
authors.lastname: Wienands
authors.forename: Bertram
authors.initials: B
authors.lastname: Glass
mesh_terms: D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D058846:Antibodies, Monoclonal, Murine-Derived; D000920:Antibody-Dependent Cell Cytotoxicity / Q000187:drug effects* / Q000276:immunology; D018951:Antigens, CD20 / Q000276:immunology / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology; D002460:Cell Line; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D015236:HLA-C Antigens / Q000378:metabolism; D015395:Histocompatibility Antigens Class I / Q000378:metabolism*; D006801:Humans; D020014:K562 Cells; D007694:Killer Cells, Natural / Q000276:immunology / Q000378:metabolism*; D008213:Lymphocyte Activation / Q000187:drug effects / Q000276:immunology; D008214:Lymphocytes / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D016393:Lymphoma, B-Cell / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D054340:Receptors, KIR / Q000276:immunology / Q000378:metabolism; D054342:Receptors, KIR2DL1 / Q000276:immunology / Q000378:metabolism; D054343:Receptors, KIR2DL2 / Q000276:immunology / Q000378:metabolism; D054344:Receptors, KIR2DL3 / Q000276:immunology / Q000378:metabolism; D000069283:Rituximab
chemical_list: D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; D018951:Antigens, CD20; D000970:Antineoplastic Agents; D015236:HLA-C Antigens; D015395:Histocompatibility Antigens Class I; C093100:KIR2DL1 protein, human; C515077:KIR2DL2 protein, human; C515078:KIR2DL3 protein, human; D054340:Receptors, KIR; D054342:Receptors, KIR2DL1; D054343:Receptors, KIR2DL2; D054344:Receptors, KIR2DL3; D000069283:Rituximab