ISOLATION AND PARTIAL CHARACTERIZATION OF RADIOIODINATED MYELOBLASTIC LEUKEMIA-ASSOCIATED CELL-SURFACE GLYCOPROTEIN ANTIGEN

Abstract

Peripheral blood myeloblasts from 5 patients with acute myeloblastic leukemia and peripheral remission leukocytes from 2 of these patients were radiolabeled by the lactoperoxidase-catalyzed surface radioiodination technique and incubated in a nutrient medium at 37.degree. C. Radioactive materials shed from viable cells into the supernatant at 24 h were purified by gel filtration and DEAE-cellulose chromatography. The radiolabeled leukemic cells shed relatively few molecular species into the culture medium. The DEAE-cellulose eluate usually contained 1 major peak in which radioactivity and protein levels were coincident; the MW of this compound was 350,000-400,000, and it contained carbohydrate and protein. Glycoprotein shed from leukemic cells was specifically reactive in a coprecipitation assay with defined antimyeloblast alloantisera obtained from leukemic patients receiving immunotherapy. No reaction was seen with antisera directed against HLA or B[bone marrow derived]-cell antigens. Material shed from remission cells did not coprecipitate with antileukemic antisera. The isolation of radioactively labeled antigen derived from myeloblasts may ultimately allow the monitoring of human antigen levels in leukemic blood by radioimmunoassay.