Cytokines and cytotoxic pathways in engraftment resistance to purified allogeneic hematopoietic stem cells

Abstract

The way that allogeneic hematopoietic cells are rejected is not completely understood. Regimen-resistant populations, including natural killer (NK) cells and lymphocytes, are thought to mediate the allograft barrier. In this report, the mechanism by which recipient cell populations resist engraftment of purified allogeneic hematopoietic stem cells (HSCs) was examined in mice. To define the immunoregulatory pathways involved in allogeneic hematopoietic cell resistance, HSC transplantations were performed in immune-defective recipients. Recipients were wild-type mice treated with alpha-NK cell antibodies or knockout strain mice lacking expression of CD8, perforin, Fas ligand, or 1 of the following cytokines: tumor necrosis factor alpha, transforming growth factor beta, interferon gamma, interleukin 4, or interleukin 10. Elimination of a single cytotoxic pathway was ineffective in reducing engraftment resistance, although mice treated with a polyclonal antibody that recognizes NK-cell determinants or CD8 expression showed a profound reduction in the engraftment barrier. Posttransplantation chimerism analysis revealed regeneration of host hematopoiesis in some experimental groups. These studies show, for the first time, that elimination of selected cytokines does not alter allogeneic hematopoietic resistance. Furthermore, the chimerism data reinforce the importance of competition for HSC niches in conjunction with immune mechanisms in resistance to long-term HSC engraftment.

Expansion of donor-reactive host T cells in primary graft failure after allogeneic hematopoietic SCT following reduced-intensity conditioning

“…We found graft rejection was associated with an increase in numbers of host T cells in the peripheral blood three weeks after BMT and expansion of cytotoxic CD8 þ T cells in the hematopoietic tissues, BM and spleen. These results correspond with the previous experimental studies that CD8-deficient recipient mice were superior for engraftment 32,33 and that preconditioning with anti-CD8 mAb enhanced allogeneic engraftment. 34 Given that host T cells selectively targeted donor-type cells (Figure 2), these host T cells should recognize donor-type MHC and minor histocompatibility antigens directly presented on donor APCs or indirectly presented on host APCs.…”

Ex Vivo Rapamycin Generates Apoptosis-Resistant Donor Th2 Cells That Persist In Vivo and Prevent Hemopoietic Stem Cell Graft Rejection

“…It is important to note that a determination of the molecular mechanism accounting for graft rejection has been elusive, since cytokine-and cytolytic-deficient host T cells have retained a capacity to cause rejection, including IFN-␥-deficient T cells (56). Furthermore, even host T cells deficient in multiple cytolytic molecules can mediate rejection (57).…”

A chromosome 16 quantitative trait locus regulates allogeneic bone marrow engraftment in nonmyeloablated mice

“…For some experiments, recipient mice were also injected intraperitoneally with 1500 g anti-CD4 (GK1.5) and/or 1500 g anti-CD8 (53-6.7) monoclonal antibodies given in 3 divided doses on days Ϫ3, Ϫ2, and Ϫ1; polyclonal anti-asialo-GM1 (Wako Chemical) 100 g intravenously on day Ϫ7 and 100 g intraperitoneally on day Ϫ1 as described 3 ; or control rat IgG (Sigma-Aldrich). Anti-CD4 and anti-CD8 monoclonal antibodies were obtained by culturing the respective hybridomas in 15% fetal bovine serum in a CellLine flask-based bioreactor (Integra Biosciences) and purified by protein G (Amersham Biosciences) affinity chromatography.…”

“…1,2 Elimination of donor hematopoietic cells by these immune cell populations likely requires cytolytic mechanisms, such as granzyme and perforin. However, key cytolytic pathways have not been identified, because neutralization of each singly, 3,4 or even several simultaneously, 5,6 fails to eliminate engraftment barriers. In addition, nonimmune elements related to bone marrow (BM) "space" and hematopoietic stem cell (HSC) niche interactions likely contribute to engraftment barriers 7,8 and further confound efforts to study their underlying biology.…”