Forkhead box protein P1 is a transcription factor that belongs to subfamily P of the forkhead box transcription factors. It plays a role in normal developmental events, including the control of cellular differentiation and proliferation, immune regulation and signal transduction. Furthermore it is involved in carcinogenesis. This antibody detects activated B cells in the mantle zone and germinal center (lymph node) as well as diffuse large B-cell lymphomas and extranodal marginal zone B cell lymphomas of MALT.