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N Dainiak, G Warren, D Sutter, S Kreczko and D Howard
Department of Medicine, St Elizabeth's Hospital, Boston, MA 02135.
A monoclonal antibody (MoAb) recognizing a membrane-associated erythroid
burst-promoting factor was prepared by immunizing BALB/c mice with plasma
membrane-derived vesicles exfoliated from lymphocytes under serum-free
conditions. Hybrids secreting antibody reactive with lymphocyte plasma
membranes were formally cloned and IgG was purified from monoclonal
supernatants or from BALB/c mouse ascites fluid. Two clones (D3-E4 and
D3-G9) were found to suppress burst forming unit- erythroid (BFU-E)
proliferation when added directly to serum-free human marrow culture.
Inhibition to a level of 100% was observed in a dose- dependent fashion
over a wide range of antibody concentrations (0-200 micrograms/mL). Neither
antibody altered the proliferation of colony forming unit-granulocyte
macrophage (CFU-GM) or colony forming unit-
granulocyte-erythroid-monocyte-megakaryocyte (CFU-GEMM) progenitor cells in
human bone marrow culture. The D3-E4 clone was found to produce an IgG1
antibody which adsorbs an erythroid burst-promoting activity (BPA) from
supernatants of, and octylglucoside extracts of shed vesicles present in,
serum-free, lymphocyte conditioned medium (LCM), and which recognizes a
vesicular protein of Mr approximate 30,000 on immunoblots of membrane
proteins electrophoresed on sodium dodecyl sulfate (SDS)/polyacrylamide and
transferred to nitrocellulose. In contrast, the D3-G9 clone was found to
produce an IgG1 cytotoxic antibody. These antibodies will be important to
the study of cell-cell and growth factor-cell interactions in vitro.
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