Effects of natalizumab on circulating B cells, T regulatory cells and natural killer cells.

Background: Natalizumab is a humanized monoclonal antibody directed against very late activation antigen 4 (VLA-4) and has a potent effect on disease activity in multiple sclerosis. Blockade of VLA-4 with natalizumab may not only interfere with autoimmunological mechanisms but also with central nervous system immune surveillance.

Methods: Longitudinal ex vivo and in vitro study to determine the effect of natalizumab on the frequency of distinct immune cells and on the frequency and suppressive function of natural CD4+CD25+ regulatory T cells (Tregs).