Oct-2 is a transcription factor belonging to the POU homeo-domain family that binds to the Ig gene octomer sites regulating B cell specific genes. It is dependent on the activity of B cell restricted coactivators such as BOB.1/OBF.1 Oct-2 protein expression is not restricted to B cells, although expression levels are much higher in these cells. Antibodies to Oct-2 are a useful additional marker for the recognition of B cells and B cell derived lymphomas.