Evaluation of Constitutive or Induced Activation State of the VLA-4 Integrin in Human and Murine Samples

The integrin heterodimer CD49d/CD29 (a.k.a. Very Late Antigen-4, VLA-4) mediates cell-cell and cell-matrix interaction through binding to its specific ligands. VLA-4 can be present on the cell surface at different conformation states that affect the binding affinity for the ligands. In chronic lymphocytic leukemia (CLL), higher VLA-4 levels have been demonstrated to be associated with a worse prognosis both in the chemo-immunotherapy era and in the BCR inhibitor setting, in keeping with the role of VLA-4 as a key molecule favoring CLL cell localization in protective niches of bone marrow and lymph nodes. Here, we describe functional flow cytometry-based methods to assess the activation state of the VLA-4 integrin, applicable in both human and murine settings, as well as in fresh or thawed samples. A specific "R" script for analyzing flow cytometry data is also provided.