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Updated: May 22, 2026
Static Adhesion Assay for the Study of Integrin Activation in T Lymphocytes
Published on: June 13, 2014
Transient lymphocyte decrease due to adhesion and migration following catumaxomab (anti-EpCAM x anti-CD3) treatment
Kirsten Dettmar1, Isabell Seitz-Merwald, Carsten Lindemann
1Fresenius Biotech GmbH, Frankfurter Ring 193a, 80807 Munich, Germany.
Insights
Catumaxomab causes a temporary drop in lymphocyte counts by increasing T cell adhesion to endothelial cells. This redistribution of lymphocytes is reversible and explains the observed clinical effect.
Area of Science:
- Immunology
- Oncology
- Pharmacology
Background:
- A transient decrease in peripheral blood lymphocyte counts was observed in patients after intraperitoneal administration of the trifunctional monoclonal antibody catumaxomab (anti-EpCAM x anti-CD3).
- The underlying mechanism for this observed effect required further investigation.
Purpose of the Study:
- To investigate the effect of catumaxomab on lymphocyte counts in a preclinical mouse model.
- To elucidate the in vitro mechanism of action responsible for the observed lymphocyte redistribution.
Main Methods:
- Administration of a related antibody (BiLu) to mice to analyze blood leukocytes.
- In vitro studies using human peripheral blood mononuclear cells (PBMC) to assess T cell activation, cytokine secretion, and adhesion to endothelial cells.
- Flow cytometry was used to quantify adherent T cells.
Main Results:
- BiLu treatment in mice led to a dose-dependent, transient decrease in CD3+ T cells (CD4+ and CD8+), with counts normalizing within 48 hours.
- Catumaxomab induced T cell activation (CD69 expression) and cytokine release (TNFα, IFNγ) in vitro.
- Catumaxomab dose-dependently enhanced T cell adhesion to endothelial cells, further increased by TNFα-induced endothelial cell activation.
Conclusions:
- Catumaxomab enhances T cell adhesion to endothelial cells via antibody-mediated T cell activation and subsequent cytokine production.
- This mechanism, involving upregulation of endothelial cell adhesion molecules, explains the transient, reversible decrease in lymphocyte counts observed in patients.
- The findings suggest lymphocyte redistribution as the cause for the observed clinical effect.
Introduction:
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.
Materials And 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.
