T-cell depletion of allogeneic bone marrow using anti-alpha beta TCR monoclonal antibody: Prevention of graft-versus-host disease without affecting engraftment potential in rats

Bone marrow chimerism may solve two major limitations in the transplantatio n of solid organs and cellular grafts: (1) the requirement for life-long im munosuppressive therapy, and (2) acute and chronic rejection, When untreate d bone marrow is transplanted into major histocompatibility complex (MHC)-d isparate rats, lethal graft-vs-host disease (GVHD) occurs in the majority o f recipients. T-cell depletion using anti-CD3 and anti-CDS monoclonal antib ody (mAb) to avoid GVHD led to an increased occurrence of failure of engraf tment, We previously identified a cellular population in mouse bone marrow that facilitates engraftment of highly purified hematopoietic stent cells ( HSC) across complete MHC barriers. In light of the fact that facilitating c ells have a CD8(+)/CD3(+)/TCR- phenotype and mostly coexpress CD5, we evalu ated in this study whether T-cell depletion of rat hone marrow using anti-a lpha beta TCR mAb would retain engraftment potential Set avoid GVHD, T-cell depiction of bone marrow was performed using anti-alpha beta TCR mAb and i mmunomagnetic beads, Recipients were conditioned with 1100 or 1000 cGy of t otal body irradiation and reconstituted with 100 X 10(6) T-cell depleted (T CD) MHC- and minor antigen-disparate bone marrow cells, Animals were monito red clinically and histologically for GVHD. Chimerism was assessed by flow cytometry, Immunomagnetic bead depletion resulted in a reduction of T cells from 1.92% +/- 0.21% to 0.10% +/- 0.04% of total bone marrow, T-cell deple tion did not remove facilitating cells (CD8(+)/alpha beta TCR-/gamma delta TCR-/NK3.2.3(-)) from bone marrow. Further, the engraftment potential of TC D bone marrow was not affected, as 100% of animals engrafted and high level s of donor chimerism were detectable. Animals reconstituted with TCD bone m arrow showed no clinical evidence of GVHD and histology revealed none to mi nimal changes, whereas recipients transplanted with untreated bone marrow s uccumbed to severe lethal GVHD. T-cell depletion using anti-alpha beta TCR mAb and immunomagnetic beads selectively removes T cells from the bone marr ow graft while sparing facilitating cells that are required for engraftment of allogeneic bone marrow across MHC barriers. Moreover, the cells require d for engraftment of HSC do not produce GVHD, (C) 1999 International Societ y for Experimental Hematology. Published by Elsevier Science Inc.