Conventional dendritic cells are the critical donor APC presenting alloantigen after experimental bone marrow transplantation

Abstract

We have quantified the relative contribution of donor antigen-presenting cell populations to alloantigen presentation after bone marrow transplantation (BMT) by using transgenic T cells that can respond to host-derived alloantigen presented within the donor major histocompatibility complex. We also used additional transgenic/knockout donor mice and/or monoclonal antibodies that allowed conditional depletion of conventional dendritic cells (cDCs), plasmacytoid DC (pDCs), macrophages, or B cells. Using these systems, we demonstrate that donor cDCs are the critical population presenting alloantigen after BMT, whereas pDCs and macrophages do not make a significant contribution in isolation. In addition, alloantigen presentation was significantly enhanced in the absence of donor B cells, confirming a regulatory role for these cells early after transplantation. These data have major implications for the design of therapeutic strategies post-BMT, and suggest that cDC depletion and the promotion of B-cell reconstitution may be beneficial tools for the control of alloreactivity. IntroductionRecognition of host alloantigen (alloAg) by donor T cells commonly results in graft-versus-host disease (GVHD), which is a key contributor to the high mortality associated with bone marrow transplantation (BMT). GVHD is initiated by residual host antigen-presenting cells (APCs) that directly present host antigen (Ag) to donor T cells. 1 Subsequent Ag presentation is mediated by donor APCs, which present host Ag to donor T cells via the indirect pathway of antigen presentation, predominantly via major histocompatibility complex (MHC) class II to CD4 T cells. The APC populations contributing to this effect and the rate at which this process occurs after BMT are unclear. Using novel reagents, we demonstrate that donor conventional dendritic cells (cDCs) are the primary APCs responsible for indirect presentation of alloantigen after BMT, and this process commences almost immediately after transplantation. Methods MiceFemale C57BL/6 (B6, H-2 b , CD45.2 ϩ ), B6.Ptprc a (H-2 b , CD45.1 ϩ ), and BALB/c (H-2 d , CD45.2 ϩ ) mice were purchased from the Animal Resource Center (Perth, Australia). B cell-deficient (B6.MT; H-2 b , CD45.2 ϩ ) mice were bred at the Queensland Institute of Medical Research (QIMR; Brisbane, Australia). B6.CD11c.DTR transgenic (Tg) mice (where the diphtheria toxiin [DT] receptor and enhanced green fluorescent protein [EGFP] are driven off the CD11c promoter) and congenic BALB/c mice (H-2 d , CD45.1 ϩ ) were bred at the Herston Medical Research Centre (Brisbane, Australia). Macrophage-Fas-induced apoptosis (MAFIA) Tg (B6.MAFIA, H-2 b , CD45.2 ϩ ; where Fas and EGFP are driven off the c-fms promoter) were provided by A.R.P. In the CD11c.DTR mouse, administration of DT leads to systemic depletion of donor cDCs in treated animals, as evidenced by examination of spleen, peripheral/mesenteric lymph nodes, skin, and lung. [2][3][4][5] We have also confirmed cDC depletion in liver (data not shown). In the MAFIA mouse, the sys...

Plasmacytoid Dendritic Cells Play a Major Role in Apoptotic Leukocyte-Induced Immune Modulation

“…infusion of diphtheria toxin (DT; 100 ng per mouse; Sigma Aldrich). This treatment allows short-term ablation of CD11c high DCs (7, 21) without significantly affecting PDCs (22). PDC depletion was performed using purified anti-mouse PDCA-1 mAb i.p.…”

Siglec-G–CD24 axis controls the severity of graft-versus-host disease in mice

“…This is particularly critical in light of the recent observations, which demonstrate that the absence of any one subset of professional host-derived hematopoietic APCs, such as DCs or macrophages, contrary to the expectations of reducing donor T-cell responses, are either irrelevant, or actually enhance donor T-cell responses and accentuate GVHD severity. [18][19][20][21][22] These newer observations suggest that pathways that mitigate the hematopoietic APCs may be as critical for attenuating GVHD.…”

Cross-Dressing by Donor Dendritic Cells after Allogeneic Bone Marrow Transplantation Contributes to Formation of the Immunological Synapse and Maximizes Responses to Indirectly Presented Antigen

“…Mice were transplanted [6total body irradiation (TBI)] on day 0, as previously described (4,6). B6D2F1, B6, and BALB/c background animals received 1100 cGy, 1000 cGy, and 900 cGy total doses, respectively.…”

“…GVHD remains one of the key complications of BMT as therapy for hematological malignancy, and despite advances in the field, further insights into disease pathogenesis remain important for design of therapeutic strategies. Donor alloreactive T cells may be stimulated by direct interaction with host-type MHC from either hematopoietic or nonhematopoietic sources (2,3) or by donor cells presenting processed, acquired Ag via the indirect pathway (2,(4)(5)(6). In addition to these two classical pathways, we have been interested in the semidirect pathway of Ag presentation, whereby a donor APC which has acquired MHC of host-type, via "trogocytosis" or "cross-dressing" could potentially stimulate antihost responses from donor T cells (7)(8)(9).…”