Clinical applications of CD34(+) peripheral blood progenitor cells (PBPC)

Recently, a number of devices have been developed for the positive selectio n of CD34(+) peripheral blood progenitor cells (PBPC) for clinical use in a utologous or allogeneic transplantation. The rationale for CD34(+) selectio n is based on clinical studies shelving a tmo- to five-log reduction of con taminating tumor cells in patients with breast cancer, multiple myeloma and low-grade lymphoma. In addition, a three- to five-log reduction of T cells can be obtained by CD34(+) selection in both autologous grafts for patient s with autoimmune disease resistant to conventional therapy and allogeneic grafts to reduce the incidence and severity of acute graft-versus-host dise ase. Transplantation of positively selected autologous CD34(+) PBPC results in a rapid and stable neutrophil and platelet engraftment in patients who recei ved an infused dose of at least 2.0 x 10(6) CD34(+) cells/kg. Results from randomized trials suggest that time to engraftment is not different compare d to unmanipulated PBPC autografts. However, close monitoring for infectiou s complications (e.g., cytomegalovirus disease) is required. Allogeneic CD3 4(+) PBPC have also been successfully transplanted and, using novel technol ogies, megadoses of purified CD34(+) PBPC can be obtained and used to overc ome histocompatibility differences between allogeneic donor and patient res ulting in stable engraftment, even in a haploidentical setting. Additional randomized phase III trials are required to deter mine whether tumor cell p urging or lymphocyte depletion by CD34(+) cell selection will have a signif icant impact on progression-free and overall survival in both autologous an d allogeneic transplantation.