Double T cell depletion of bone marrow using sequential positive and negative cell immunoaffinity or CD34+ cell selection followed by Campath-1M; effect on CD34+ cells and progenitor cell recoveries.
An advantage of CD34+ cell selection over antibody purging is that a component allograft is produced comprising a stem cell enriched and an unadsorbed fraction, the latter containing T cells which may be used for post-transplant immunotherapy. Initial reports with PBSC allografts suggested that T cell depletion (TCD) by CD34+ cell selection and post-graft cyclosporin A +/- methotrexate was insufficient prophylaxis against acute GVHD. We compared sequential TCD (of a CD34+ cell-selected fraction) using a second (CD2) immunoaffinity step or Campath-1M monoclonal antibody and complement. Since a high stem cell 'dose' enhances engraftment across HLA barriers and improves overall post-transplant outcome, the recovery of CD34+ cells and progenitors were assessed. Sequential positive (CD34+) and negative (CD2+) immunoaffinity selection resulted in a 3.4 log depletion of T cells as compared to a 4.05 log depletion when CD34+ cell selection was followed by Campath-1M treatment. Recoveries of CD34+ cells, CFU-GM and BFU-E following double depletion using CD34+ cell selection plus CD2+ cell depletion were 28, 25 and 17% as compared to 20, 18 and 16% when CD34+ cells were treated with Campath-1M. The unadsorbed fraction contained 85% of the original T cells, from which donor leukocyte infusions in the range of 10(5) to 10(7) CD3+ cells per kg body weight of the recipient were harvested. Despite the advantages of component allografts, the loss of stem/progenitor cells may restrict sequential TCD steps unless single BM harvests are supplemented and/or replaced with mobilised PBSCs.
Clarke
E
E
Bristol Institute for Transfusion Sciences, National Blood Service - Bristol Centre, UK.
Potter
M N
MN
Hale
G
G
Waldmann
H
H
Lankester
A
A
Cornish
J M
JM
Steward
C G
CG
Marks
D I
DI
Oakhill
A
A
Pamphilon
D H
DH
D000074323:Alemtuzumab; D000911:Antibodies, Monoclonal / Q000276:immunology / Q000494:pharmacology*; D061067:Antibodies, Monoclonal, Humanized; D000912:Antibodies, Neoplasm; D018952:Antigens, CD34; D016465:Bone Marrow Purging; D016026:Bone Marrow Transplantation; D019650:Hematopoietic Stem Cell Mobilization / Q000379:methods*; D018380:Hematopoietic Stem Cell Transplantation; D006801:Humans; D007163:Immunosorbent Techniques; D008212:Lymphocyte Depletion / Q000379:methods*; D013601:T-Lymphocytes / Q000276:immunology; D014182:Transplantation, Autologous; D014184:Transplantation, Homologous
D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000912:Antibodies, Neoplasm; D018952:Antigens, CD34; D000074323:Alemtuzumab