The Lactate Dehydrogenases of Hemopoietic Cells

In summary we have demonstrated that hemopoietic stem cells of man contain all five isoenzymes, and not a single pure type. Our data and the results of others obtained from fetal tissue also indicate that embryonic LDH of man exists as multiple forms. We have demonstrated that differentiation, with respect to LDH isoenzymes, of stem cells along erythrocytic, granulocytic, and lymphocytic lines, occurs in different sequences. It appears that LDH-1 synthesis is necessary in mitotic granulocytic cells, but ceases at the metamyelocyte level where LDH-5 synthesis begins. LDH-5 synthesis occurs in early erythroid cells and probably ceases at the reticulocyte level.²⁷ This is not accompanied by stimulation of LDH-1 synthesis. The maturation of lymphocytes is characterized by a stimulation of LDH-5 synthesis, which is not diminished in the normal circulating cell. Lymphocytes obtained from normal individuals and cultured in vitro in the presence of phytohemagglutinin demonstrate reversion of LDH patterns to those seen in acute leukemias. Our data further indicate that the isoenzyme pattern obtained from hemopoietic cells are indicative of the degree of cellular differentiation, and substantiate the concept of a defective differentiation and maturation process in acute leukemic cells.