High-speed (80,000 × 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 labeled 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 patients. Immunofluorescent-positive cells, members of the myelocytic 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 diseases 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 antigen(s).
Supported in part by a grant from the John A. Hartford Foundation, by Research Grant CA-07745 and by Research Contracts PH 43-63-43 and PH 43-63-593 from the USPHS.