Abstract
This study analyses the activity of 95 antisera raised in rabbits against human leukaemic myeloblasts. A number of different means were used to immunize both normal rabbits and rabbits which had been treated to render them tolerant of normal human splenic leucocytes. Different immunization schedules included the use of different doses of untreated myeloblasts, as well as myeloblasts treated with neuraminidase, antibody against human spleen cells or glutaraldehyde. Analysis of the sera was carried out using two sensitive techniques for detecting cell surface antigens: a radioactive anti-immunoglobulin binding assay using 125I-horse-F(ab')2-anti-rabbit-Fab and a K-cell-mediated cytotoxicity test using rat spleen cells as effectors. (i) The unabsorbed sera showed similar mean titres against leukaemic myeloblasts and normal splenocytes. (ii) Extensive absorption with pooled cadaveric spleen were required to remove antibody against polymorphic antigens. (iii) 17/95 antisera had activity against at least some leukaemic myeloblasts after extensive absorption with cadaveric spleen. (iv) Some of the 17 absorbed sera with selective activity for myeloblasts also reacted against PHA-induced lymphoblasts. (v) Although the 17 absorbed sera showed little or no activity against marrow in the above assays normal human marrow totally absorbed all residual activity in these sera against leukaemic myeloblasts. We conclude that although these sera contain activity against antigens common to leukaemic myeloblasts and a minority population of normal marrow cells, they have no detectable activity against leukaemic-specific antigens.