An alternate origin for the placental isoenzyme of alkaline phosphatase

By means of an electrofocusing technique, the serum specimens of pregnant women routinely revealed three bands of alkaline phosphatase (ALP) that were released by placental syncytiotrophoblast, germ cell (ovary), and fetal intestine at pl of 4.73, 4.65, and 4.55, respectively. When defining reference ranges for ostensibly healthy persons of all decades of age and investigating patients with elevated total ALP activity, we found the isoenzyme at pl 4.73 to be above the established reference range in some nonpregnant women and in men. Evidence suggests that T lymphocytes from whole blood or in vivo tissue were the origin of this pl 4.73 ALP band; the isoenzyme being released during cell lysis, in cellular turmoil from any cause, or when active cell division occurs. A designation of lymphocyte ALP is proposed for this ALP band that is observed in a broad group of diseases associated with abnormal lymphocyte function.