Lymphocyte transformation in leukemic serum

Cultures of normal lymphocytes were induced to transform by pokeweed mitogen (PWM). Inhibition of transformation was observed when these cultures contained sera isolated from children with acute lymphoblastic leukemia (ALL). The inhibition of transformation of normal lymphocytes was best demonstrated when the concentration of the leukemic serum in the culture medium was relatively high (60 percent); however, the inhibition was also observed with a more standard serum concentration (20 percent). Not all leukemic sera were inhibitory. Pretreatment sera from newly diagnosed patients with leukocyte counts greater than 50,000/mm3 were significantly inhibitory. Pretreatment sera from newly diagnosed patients with leukocyte counts less than 50,000/mm3, and sera from patients in remission or relapse had no significant effect. The inhibition observed with the sera of the high leukocyte count group was not believed to be related to cytotoxicity. The significance of this inhibitor in relation to clinical prognosis needs to be investigated.