Cross-reaction between antigens of human myelogenous leukemia and Mason-Pfizer monkey virus

An antigen similar to a major protein of Mason-Pfizer monkey virus (MPMV) was found in breast cancers of 2 out of 9 women and in splenic tissue or peripheral leukocytes from 12 of 12 patients with myelogenous leukemias. Such antigen was not detected in other tumors or normal tissues. The cross-reactivity was detected using inhibition of the indirect quantitative radioimmunoprecipitation of ¹²⁵I-labeled purified MPMV p25 and anti-MPMV antiserum. Particles banding in a density region of 1·15 to 1·17 g/ml, the density characteristic of the known animal leukemia viruses, were used as inhibitors for the precipitation. An antigen isolated from a spleen of a patient with myelogenous leukemia using anti-p25 immunoabsorbent column was similar in net electrical charge and molecular weight to MPMV p25. These results suggest that a virus-like particle bearing some antigenic relatedness to MPMV may be potentially important in the pathogenesis of human myelogenous leukemia.