T cell depletion of human bone marrow using an oxidase-peroxidase enzyme immunotoxin

We have shown in a previous paper that an antibody-enzyme immunotoxin (eIT) constructed by chemically coupling the 097 monoclonal antibody to glucose oxidase and to lactoperoxidase (097 eIT) effectively eliminated T cells of human peripheral blood origin and killed cultured human thymoma cells. Here we tested its effectiveness against T cells present in human bone marrow cell suspensions contaminated by large numbers of erythrocytes. The T cell-depleting capacity of the 097 eIT was assessed by means of four different assay methods, three of which gave concordant results and indicated an effective depletion comparable in efficiency to published work. For example, by limiting dilution analysis assay of IL-2-producing T cells we found approximately 3 logs of T cell depletion. The growth of bone marrow stem cells (CFU-GM, CFU-E and BFU-E) was not affected by treatment with the 097 conjugates.