Ortlieb Guerreiro-Cacais Andre ⁎ , Beyeen Amennai, Jagodic Maja, Olsson Thomas Department of Clinical Neuroscience, Neuroimmunology Unit, Karolinska Institutet, Stockholm, Sweden VAV1, a member of the family of guanine nucleotide exchange factors (GEF) for the Rho family of GTP binding proteins, is important in hematopoiesis, also playing a role in T-cell and B-cell development, activation, tissue homing and effector function.