Enzyme activity in human mononuclear blood cells.

Two different kinds of mononuclear blood cell samples (mixed blood cell population consisting of lymphocytes, monocytes, and platelets; pure lymphocyte population) were tested for enzyme activity of mitochondrial malic enzyme, peptidase A, and alpha-fucosidase. None of the three enzymes was demonstrable in the pure lymphocyte preparation; the mixed cell population, however, exhibited a distinct enzyme activity. Positive reactivity is thus obviously dependent upon monocytes and/or platelets.