Alkaline phosphatase (AP) is a universal pluripotent marker for all types of pluripotent stem cells including embryonic stem cells, embryonic germ cells, and induced pluripotent stem cells. The pluripotent status of stem cells can be characterized by a high level of AP expression, along with the expression of multiple pluripotency markers including the transcription factors Nanog, Oct4, Sox2, stage-specific embryonic antigens, SSEA-1, -3, -4, and tumor-related antigens, TRA-1-60, TRA-1-81.