Human beta-globulin factors affecting growth of human lymphocytes and mouse fibroblasts

Evidence is presented to show the existence in human beta-globulin (Cohn fraction III) of 2 growth-promoting factors that stimulate DNA synthesis and cell division in human lymphocytes and 3T3 B mouse fibroblasts. After extraction of human beta-globulins at pH 3.0 in 0.1 M NaCl followed by sieve chromatography on Sephadex, 2 distinct fractions were obtained containing the biological activity; one of polypeptide nature and molecular weight of approx. 10 000 Daltons and the other consisting of a homogeneous ribonucleic acid, as revealed by polyacrylamide gel electrophoresis. The above-mentioned factors appear to lack both cell and species specificity, since they are mitogenic agents for cells as diverse as mouse fibroblasts and human lymphocytes.