title: Transient lymphocyte decrease due to adhesion and migration following catumaxomab (anti-EpCAM x anti-CD3) treatment in vivo.
abstract: BACKGROUND
  In patients, a transient decrease in peripheral blood lymphocyte counts was observed following intraperitoneal administration of the trifunctional monoclonal antibody catumaxomab (anti-human EpCAM x anti-human CD3). The aim of this study was to clarify the observed effect in a preclinical mouse model and to analyse the related mechanism of action in vitro.
  
  
  METHODS
  A related antibody, BiLu (antihuman EpCAM x anti-mouse CD3), was administered to mice and blood leukocytes were analysed. In vitro studies measured activation and cytokine secretion from human peripheral blood mononuclear cells (PBMC). For the analysis of T cell adhesion, PBMC were preincubated with catumaxomab and then co-cultured with human endothelial cells (HUVEC); T cell adhesion was assessed in the presence or absence of endothelial cell preactivation by TNFα. Adherent T cells were determined by flow cytometry.
  
  
  RESULTS
  Treatment of mice with BiLu resulted in a dosedependent transient decrease in CD3+ T cells (both CD4+ and CD8+) that returned to the normal range within 48 h. Catumaxomab physiologically activated T cells in vitro (increased CD69 expression) and induced cytokine release (TNFα, IFNγ). TNFα increased expression of adhesion molecules CD54 and CD62E on endothelial cells. Furthermore, catumaxomab dose-dependently enhanced adhesion of T cells to endothelial cells. Adhesion was further increased when endothelial cells were preactivated with TNFα.
  
  
  CONCLUSIONS
  Catumaxomab increases adhesion of T cells to endothelial cells due to antibody-mediated activation of T cells and production of T cell cytokines that up-regulate endothelial cell adhesion molecules. These results provide a mechanistic rationale for the transient, reversible decrease in lymphocyte counts observed following catumaxomab administration in patients, which is likely to be due to redistribution of lymphocytes.
authors.affiliation: Fresenius Biotech GmbH, Frankfurter Ring 193a, 80807 Munich, Germany.
authors.forename: Kirsten
authors.initials: K
authors.lastname: Dettmar
authors.forename: Isabell
authors.initials: I
authors.lastname: Seitz-Merwald
authors.forename: Carsten
authors.initials: C
authors.lastname: Lindemann
authors.forename: Petra
authors.initials: P
authors.lastname: Schroeder
authors.forename: Diane
authors.initials: D
authors.lastname: Seimetz
authors.forename: Judith
authors.initials: J
authors.lastname: Atz
mesh_terms: D000818:Animals; D018033:Antibodies, Bispecific / Q000494:pharmacology*; D000951:Antigens, Neoplasm / Q000276:immunology; D017252:CD3 Complex / Q000276:immunology; D002448:Cell Adhesion / Q000276:immunology*; D015815:Cell Adhesion Molecules / Q000276:immunology; D002465:Cell Movement / Q000276:immunology*; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism; D000071858:Epithelial Cell Adhesion Molecule; D005260:Female; D005434:Flow Cytometry; D061307:Human Umbilical Vein Endothelial Cells / Q000166:cytology* / Q000187:drug effects / Q000276:immunology; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000166:cytology* / Q000187:drug effects / Q000276:immunology; D008213:Lymphocyte Activation / Q000187:drug effects; D051379:Mice; D008807:Mice, Inbred BALB C; D013601:T-Lymphocytes / Q000166:cytology* / Q000187:drug effects / Q000276:immunology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D018033:Antibodies, Bispecific; D000951:Antigens, Neoplasm; D017252:CD3 Complex; D015815:Cell Adhesion Molecules; D016207:Cytokines; D000071858:Epithelial Cell Adhesion Molecule; D014409:Tumor Necrosis Factor-alpha; C522419:catumaxomab