ABSTRACT
BACKGROUND: We previously characterized a facilitating cell (FC) in mouse marrow that enables engraftment of allogeneic hematopoietic stem cells (HSCs) without causing graft-versus-host disease (GVHD). The FC shares some cell surface molecules with T cells (Thy1+, CD3epsilon+, CD8+, CD5+, and CD2+) but is T-cell receptor (TCR) negative. Historically, depletion of CD3+ or CD8+ cells from rat marrow was associated with an increased rate of failure of engraftment. In this study, we evaluated whether depletion of alphabeta- and gammadelta-TCR(+) T cells from donor marrow would retain engraftment potential yet avoid GVHD. METHODS: Wistar-Furth rats were conditioned with 950 cGy of total body irradiation and transplanted with ACI bone marrow processed to remove either alphabeta-TCR(+), gammadelta-TCR(+), or alphabeta- plus gammadelta-TCR(+) T cells. Recipients were typed for chimerism at 28 days and monthly thereafter. RESULTS: Recipients of marrow depleted of alphabeta- (group A), gammadelta- (group B), or alphabeta- and gammadelta-TCR(+) T cells (group C) engrafted and had an average chimerism level of 73.0+/-8.3%, 92.3+/-9.2%, and 46.3+/-32.8%, respectively. Aggressive T-cell depletion did not remove the FC population (CD8+/CD3+/TCR(-)). Group A and group B both developed GVHD, with a higher incidence of GVHD in group B compared to group A. None of the recipients in group C developed GVHD. CONCLUSIONS: These data demonstrate that depletion of T cells from rat marrow does not impair engraftment of HSCs, indirectly supporting the existence of FCs in rat marrow. Moreover, donor alphabeta- and gammadelta-TCR(+) T cells contribute to GVHD in a nonredundant fashion, although alphabeta-TCR(+) T cells are more potent as the effector cells. Finally, the level of donor chimerism is influenced by the composition of the graft, because recipients of marrow that contain alphabeta-TCR(+) T cells exhibited significantly higher donor chimerism compared to recipients of marrow depleted of both alphabeta- and gammadelta-TCR(+) T cells.
Subject(s)
Bone Marrow Transplantation/immunology , Graft vs Host Disease/etiology , Receptors, Antigen, T-Cell, alpha-beta/metabolism , Receptors, Antigen, T-Cell, gamma-delta/metabolism , T-Lymphocytes/physiology , Transplantation Chimera , Animals , Graft vs Host Disease/prevention & control , Heart Transplantation/immunology , Leukapheresis , Rats , Rats, Inbred F344 , Rats, Inbred WF , Tissue Donors , Transplantation Tolerance , Transplantation, HomologousABSTRACT
Number of apparent reversals for various patterned ellipses and circles was investigated. Ellipses produced significantly more reversals than circles. Patterned stimuli produced a number of reversals dependent upon pattern orientation and corroborated predictions consistent with Power and Day's (1973) general constancy theory for apparent reversals.