CD231 is 150 kD (28-45 kD reduced) cell surface glycoprotein belonging to the Transmembrane 4 Superfamily (TM4SF also known as tetraspanins). It was originally described as T-cell Acute Lymphoblastic Leukemia Antigen (TALLA or TALLA-1). CD231 is expressed on T-cell acute lymphoblastic leukemia, neuroblastoma cells, skeletal muscle, spleen and normal brain neuron. CD231 plays a role in integrin-mediated migration, however, its biological function is not fully clear yet.