Immunofluorescent Studies in Human Leukemia1

High-speed (80,000 X g) pellets of plasma from leukemic patients and from normal individuals were used to prepare antisera in rabbits. The leukemic plasma pellets contained virus-like particles as determined by electron microscopy, whereas similar particles were not observed in the normal pellets. Globulin fractions from six antisera to normal pellets (NPA) and six antisera to leukemic pellets (LPA) were la beled with fluorescein isothiocyanate and then absorbed with normal human peripheral blood constituents and liver or spleen powders. Fully absorbed NPA preparations did not react with either normal or leukemic leukocytes, whereas fully absorbed LPA preparations yielded positive cytoplasmic reactions with peripheral leukocytes from 10 of 29 myelocytic leukemic pa tients. Immunofluorescent-positive cells, members of the mye locytic series, were found in the bone marrow of 5/5 patients with positive peripheral cells. Lymphocytic leukemic cells and cells from normal individuals or from patients with other dis eases were nonreactive, as were cultured leukocytes. The antibody activity of the LPA preparations was removed by absorption with pooled or individual normal human bone marrow powders. It was concluded that the antigens detected in immature cells of certain myelocytic leukemia patients are also present in certain normal human bone marrow cells but in concentrations too low to be accurately detected by direct immunofluorescence. The evidence is not sufficient to support the hypothesis that these antigen (s) are viral-associated an tigen (s).