Brief Report: A Plasma Factor in Chronic Lymphocytic Leukemia which Stimulates DNA Synthesis and Blastogenesis in Leukocyte Cultures

Plasmas from each of three patients with CLL and from one patient with plasma cell leukemia were added to normal leukocyte cultures and were found to stimulate DNA synthesis and blastogenesis. The stimulatory material present in plasma from one of the CLL patients was nondialyzable and could be passed through a Millipore filter of 0.22 microns pore size. It retained all or most of its activity after exposure to 60 C. for 1 hour, repeated freezing and thawing, and treatment with RNAse and DNAse.