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Mouse bone marrow and spleen cells agglutinated by soybean agglutinin (SBA) or peanut agglutinin (PNA) were previously shown to be enriched for spleen colony-forming cells (CFU-S) and sufficiently depleted of graft-versus-host reaction producing cells to allow hematologic reconstitution of lethally irradiated allogeneic recipient mice. A similar enrichment for cells capable of forming colonies in soft agar culture (CFU-C) has now been found in the SBA-agglutinated fraction of mouse bone marrow cells, in contrast to the finding that in human bone marrow the majority of the CFU-C are in the fraction not agglutinated by SBA. Cytofluorometric studies with fluorescein-labeled SBA (FITC- SBA) revealed that the majority of both mouse and human bone marrow cells bind the lectin. Experiments mixing the human marrow fractions separated by SBA reveal that true enrichment for CFU-C is achieved in the unagglutinated fraction, as opposed to a possible depletion of a suppressor cell population. Granulocytic, monocytic, and mixed cell colonies were all enriched in the SBA-unagglutinated cell fraction from human bone marrow.

Three patients with severe combined immunodeficiency (SCID) received transplants of HLA haplotype-mismatched parental bone marrow depleted of T lymphocytes by differential agglutination with soybean agglutinin (SBA) and subsequent E-rosette depletion. Two patients achieved durable engraftment with reconstitution of both humoral and cell-mediated immunity. Neither of these patients developed graft versus host disease (GVHD). The third patient achieved only a transient engraftment with concomitant development of mitogen-responsive lymphocytes of paternal origin. Our experience indicates that depletion of T lymphocytes by this technique can abrogate the potential of histoincompatible marrow grafts to induce lethal GVHD without limiting immunologic reconstitution. It also provides further evidence of nonimmune mechanisms of graft resistance that may necessitate preparative treatment of patients with SCID before transplantation with HLA- mismatched marrow cells.