Two monoclonal antibodies, prepared against a murine B lymphoma and characterized as binding to a cell surface antigen represented primarily on cells ofthe B lineage, were found to bind to human hemopoietic cells. These antibodies recognize similar populations of cells in mice and humans. Antibodies from clones 177.17 and 83.4 bound to 6% of human bone marrow nucleated cells. This included all cells with detectable cell surface Ig (sIg') and those that lack sIg but have detectable cytoplasmic ,u (sIg, cIA+), considered to be the immediate precursors of B lymphocytes (pre-B cells). In addition, these antibodies bound to a subpopulation of T cells and a proportion of null lymphocytes in marrow, spleen, and peripheral blood. An unexpected finding was that established pre-B cell lines were not recognized by these antibodies and possible reasons for this are considered. By using antibody-coated polystyrene plates for cell depletion and recovery, highly enriched preparations of ciA+, sIg-cells have been obtained. These antibodies and enrichment procedures should prove valuable in establishing the minimal requirements for maturation of these putative precursors in vitro, for comparative studies of immunodeficiency/autoimmune diseases in man and experimental animal models, and for monitoring the outcome of therapeutic marrow transplantation.A panel ofmonoclonal rat antibodies was recently prepared and characterized as directed to determinants on murine cells of B cell lineage. One group of seven clones produced antibodies that did not recognize immunoglobulin and that similarly bound to a series of established murine cell lines. Five of these made antibodies ofsatisfactory avidity and were studied in detail. The antigen(s) recognized by these antibodies is displayed on most B cells, a subpopulation of peripheral T cells, and a proportion of antibody-secreting cells (1). In addition, cell surface immunoglobulin negative (sIg-) A number ofcell surface molecules that were originally identified on murine leukocytes have been found to be analogous to human antigens. Often the basic structures-and in some cases even the cellular distributions-of these have been comparable, and there are several recent examples in which heteroantibodies and alloantibodies were found to detect conserved antigen determinants (3-9).We report here that two of our monoclonal antibodies that were prepared against murine cells bind also to human leukocytes and do so with remarkably similar selectivity for lymphocyte sets. Furthermore, these reagents can be used in the same way as with murine cells to obtain highly enriched preparations of sIg-human marrow lymphocytes. MATERIALS AND METHODSCell Suspensions. Peripheral blood and bone marrow cells were obtained from healthy adult volunteers. Histologically normal spleen samples were obtained following therapeutic splenectomy. Peripheral blood mononuclear cells were prepared by using Ficoll/Paque according to manufacturer's directions (Pharmacia). Enriched granulocytes were recovered from the ...

The surface antigen phenotype of the immediate precursors of clonable B lymphocytes was investigated with conventional alloantisera and monoclonal antibodies directed by B lineage antigens. Ia was demonstrable on B cells, but not their immediate precursors in adult marrow. Adult, but not fetal, B cell precursors were susceptible to lysis with anti-Lyb-2 or anti-Qa. A panel of monoclonal rat antibodies was prepared and placed into categories on the basis of recognition patterns obtained with established cell lines. Of 2 groups that are described here, 1 (typified by antibodies from clone 14.8) detect an antigen that is preferentially expressed on B cells and their precursors, a proportion of antibody-secreting cells, and a subpopulation of peripheral T lymphocytes. Cells that did not display demonstrable amounts of antigen include brain, granulocytes, macrophages, mastocytoma cells, and erythroleukemia cells. A 2nd category of antibodies revealed an antigen that was more widely distributed on hemopoietic cells. Cells capable of quickly maturing into functional, colony-forming B lymphocytes in culture or after transfer to irradiated recipients specifically adhered to 14.8 antibody-coated, polystyrene petri dishes in the cold. Reductions in numbers of stem cells (CFU-s) and myeloid progenitors (CFU-c) by this treatment were minimal. Of particular importance was the fact that these antibodies recognized cells in embryonic liver as well as in adults that were destined to become B lymphocytes. These observations provide new perspective on B lineage precursor heterogeneity and suggest ways of localizing and dissecting some of the earliest events that are critical to development of the humoral immune system.