Inhibitory effect of leukemic plasma on periodate-induced lymphocyte transformation

Plasma from nine out of 18 patients with untreated acute lymphoblastic leukemia (ALL) depressed the transformation of normal blood lymphocytes induced by sodium periodate (NaIO4) as judged by reduction of blast cell formation and [3H]thymidine and [3H]uridine incorporation into DNA and RNA respectively. The depressed mitogen responsiveness of lymphocytes cultured in the presence of leukemic plasma was due to the presence of inhibitory factor(s) present in the plasma rather than the absence of components present in normal plasma. The inhibitory effect of leukemic plasma on periodate-induced cell stimulation indicated that the leukemic plasma inhibitory factor(s) exert their action very rapidly and directly on the cell. Transfer of the inhibitory factor(s) from the leukemic plasma to the cultured cells was supported by the finding that the depressive action of leukemic plasma on lectin and non-lectin mitogen-induced transformation of lymphocytes was reduced if the leukemic plasma was preincubated with either resting or mitogen-treated lymphocytes prior to testing with lymphocytes not previously exposed to leukemic plasma or mitogen.